# Does wood season quicker in winter, since it’s dry?  Weird...



## thinkxingu

SO, I posted a few weeks ago asking what to do with oak that was reading around 25-30% moisture and was advised to wait another year.  Well, this morning I went and tested a couple pieces from the same batch and they're reading around 20%.  Can this be right?

Same wood batch, same moisture meter...

S


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## heffergm

Did you split a piece and test from the center? I've also found when my wood is frozen the moisture meter is useless. Always reads low. Split a piece, bring it inside to thaw and the check it.


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## mainstation

I do think that would does dry out a bit in winter, not like summer time obviously, but a local Sawmill guy around here told me that the frost and cold does draw some moisture outta the wood.  If it is windy, the wood will be seasoning.


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## Bigg_Redd

thinkxingu said:
			
		

> Does wood season quicker in winter, since it’s dry?




No.


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## LLigetfa

This debate comes up every year and rages on.  Wood certainly does continue to dry in Winter.  I see the most shrinkage on my stacks in Winter.  How much it dries in Winter versus Summer can vary a lot by region.  The RH of air in Winter can be much lower due to the wide range of temperature that precipitates out the moisture.  Winter is Nature's best dehumidifier.

The naysayers of course often use clothes on the line as an example but firewood is not clothes on the line so it's an absurd analogy.  They also use the fact heat is used in a kiln for kiln drying.  Somehow they dismiss the practice of freeze drying though.  Heat is a component in drying but aside from its use in kilns, it is generally used to change the "Relative" part of RH.  The ability of air to absorb moisture from its surrounding depends on what the RH is.  Just as heat allows air to absorb more moisture, dehumidifying air with cold also lowers RH.

Contrary to what some people think, heat does not dry air, cold does.  Heat only allows air to absorb more moisture.  Heated air returned to its previous temperature will have as much or more RH.  Cold causes moisture to condense out of the air.  Reheated chilled air will have lower RH.  That is the basic principle of dehumidifiers.


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## bsa0021

Bigg_Redd said:
			
		

> thinkxingu said:
> 
> 
> 
> 
> Does wood season quicker in winter, since it’s dry?
> 
> 
> 
> 
> 
> No.
Click to expand...

 I'd have to agree. Once it gets cold, the moisture will freeze and maybe crack the wood but the moisture will not go anywhere for the most part. Now if the wood was stored in the house the dry air would help.


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## Bigg_Redd

Of course regional particulars vary, but, all things being equal wood will dry faster the warmer it is.  

Period.  

The End.


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## f3cbboy

i live in the northeast and i think my wood dries more in the winter than it does in the summer.  it is very humid in the summer around here and the cold dry air in the winter mixed with the winds dries my wood more efficiently than the summer.


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## EKLawton

LLigetfa said:
			
		

> This debate comes up every year and rages on.  Wood certainly does continue to dry in Winter.  I see the most shrinkage on my stacks in Winter.  How much it dries in Winter versus Summer can vary a lot by region.  The RH of air in Winter can be much lower due to the wide range of temperature that precipitates out the moisture.  Winter is Nature's best dehumidifier.
> 
> The naysayers of course often use clothes on the line as an example but firewood is not clothes on the line so it's an absurd analogy.  They also use the fact heat is used in a kiln for kiln drying.  Somehow they dismiss the practice of freeze drying though.  Heat is a component in drying but aside from its use in kilns, it is generally used to change the "Relative" part of RH.  The ability of air to absorb moisture from its surrounding depends on what the RH is.  Just as heat allows air to absorb more moisture, dehumidifying air with cold also lowers RH.
> 
> Contrary to what some people think, heat does not dry air, cold does.  Heat only allows air to absorb more moisture.  Heated air returned to its previous temperature will have as much or more RH.  Cold causes moisture to condense out of the air.  Reheated chilled air will have lower RH.  That is the basic principle of dehumidifiers.


dont forget that most wood kilns use a/c to dry the air..


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## karri0n

Water freezing inside the wood expands the cells and allows the moisture to escape more quickly. That doesn't necessarily mean the wood will dry faster in winter, but a winter cycle coupled with a spring and/or summer cycle are what contribute to wood completely drying.


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## Ducati996

Wood dries all year long... its called evaporation

ever wonder were the snows goes when it melts?  same principle when wood dries.
The sun works wonders in both summer and winter


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## raybonz

LLigetfa said:
			
		

> This debate comes up every year and rages on.  Wood certainly does continue to dry in Winter.  I see the most shrinkage on my stacks in Winter.  How much it dries in Winter versus Summer can vary a lot by region.  The RH of air in Winter can be much lower due to the wide range of temperature that precipitates out the moisture.  Winter is Nature's best dehumidifier.
> 
> The naysayers of course often use clothes on the line as an example but firewood is not clothes on the line so it's an absurd analogy.  They also use the fact heat is used in a kiln for kiln drying.  Somehow they dismiss the practice of freeze drying though.  Heat is a component in drying but aside from its use in kilns, it is generally used to change the "Relative" part of RH.  The ability of air to absorb moisture from its surrounding depends on what the RH is.  Just as heat allows air to absorb more moisture, dehumidifying air with cold also lowers RH.
> 
> Contrary to what some people think, heat does not dry air, cold does.  Heat only allows air to absorb more moisture.  Heated air returned to its previous temperature will have as much or more RH.  Cold causes moisture to condense out of the air.  Reheated chilled air will have lower RH.  That is the basic principle of dehumidifiers.



That was an inciteful post... Very well thought out and some valid points were made... Just the other day watching the weather they stated that the snow was evaporating directly into the dry cold air and never melted! I have often wondered if this could happen and indeed it does! Of course the warmer the air the more moisture it can hold but in cold weather it can hold moisture also known as snow... I would also think that a dry low moisture snow on wood would tend to act like a sponge removing moisture from the wood... Good post!

Ray


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## dave11

LLigetfa said:
			
		

> This debate comes up every year and rages on.  Wood certainly does continue to dry in Winter.  I see the most shrinkage on my stacks in Winter.  How much it dries in Winter versus Summer can vary a lot by region.  The RH of air in Winter can be much lower due to the wide range of temperature that precipitates out the moisture.  Winter is Nature's best dehumidifier.
> 
> The naysayers of course often use clothes on the line as an example but firewood is not clothes on the line so it's an absurd analogy.  They also use the fact heat is used in a kiln for kiln drying.  Somehow they dismiss the practice of freeze drying though.  Heat is a component in drying but aside from its use in kilns, it is generally used to change the "Relative" part of RH.  The ability of air to absorb moisture from its surrounding depends on what the RH is.  Just as heat allows air to absorb more moisture, dehumidifying air with cold also lowers RH.
> 
> Contrary to what some people think, heat does not dry air, cold does.  Heat only allows air to absorb more moisture.  Heated air returned to its previous temperature will have as much or more RH.  Cold causes moisture to condense out of the air.  Reheated chilled air will have lower RH.  That is the basic principle of dehumidifiers.



Lligetta--I agree with you in principle, but at the risk of further inflaming this post, I know that I have read alternative statements in woodworker's publications. In fact, the Hoadley book on wood, considered a very reliable source in the woodworkers' world, refers to the drying of wood essentially stopping below a certain temperature. Going from solid water to vapor (sublimation) may occur, but I suspect not as fast as going from liquid water to vapor. And perhaps because of the structure of wood pores, in which the water has such little surface area contact with air, the net effect is to slow the drying of wood as the temp falls, no matter how dry the air. 

Don't know. Just pouring on some gasoline.


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## iceman

wood dries in the summer and in the winter --period.
summer from wind and sun 
winter from wind and sun but more from wind/and dry air ...

its really simple we understand a good windy area will dry wood.....  so if the area is just as windy in the wintertime it wont dry? 
i find pieces that are quite yet ready to burn put them aside and let winter finish drying it out!  
that BIG blizzard left us with 2-4 inches... everyone was claiing for 8-12...  it did snow!  but the air was to dry it evaporated before it hit the ground....it was 8 hrs since it was over us before we even saw a flake...


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## dave11

Well, the original question was whether wood dries FASTER in the winter than the summer. After doodling out on paper the remnants of my college chemistry classes, I'm pretty sure the answer is that the wood must dry much faster in the summer than the winter, though it will dry somewhat in the winter as well. It has to do with the amount of energy (ie. heat) required to convert solid water (ice) in the wood to water vapor, as opposed to turning liquid water (sap) into water vapor. The first requires more energy (heat) than the second, so it will take longer, especially when there is less heat to be had, namely in the winter. 

And though the analogy isn't exact, the idea is demonstrated by the example of the wet towel hung on a line. It will, in fact, dry on the line in the winter, but will do so much slower than the same towel hung on the line in 70 degree weather.


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## rdust

thinkxingu said:
			
		

> SO, I posted a few weeks ago asking what to do with oak that was reading around 25-30% moisture and was advised to wait another year.  Well, this morning I went and tested a couple pieces from the same batch and they're reading around 20%.  Can this be right?
> 
> Same wood batch, same moisture meter...
> 
> S



Your wood is frozen, bring a piece in for a while, split it and check it.  Wood will continue to season in the winter but your oak will not go from 25-30% in a few short weeks.


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## thinkxingu

Mornin',
     I thought it was strange, but it never occurred to me that the water in the wood might have frozen up--making the moisture meter not all that accurate.  Looks like I'll be re-stacking to get to the wood in back.

Side question: how much longer would it take for wood to season in a woodshed?  My racks aren't big enough to hold the amount of wood I need PLUS wood being seasoned, so I'm thinking about building a woodshed--but I can't have both.

S


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## LLigetfa

thinkxingu said:
			
		

> Side question: how much longer would it take for wood to season in a woodshed?


Side answer: It depends.

It depends on air movement, how much higher the temperature is over ambient, and the RH.  Since the wood won't get direct sun unless you build a greenhouse, you will rely on lower RH and air movement to dry the wood.


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## Wood Duck

Drying wood requires that water in the wood evaporates, and evaporation requires energy. There is a lot more energy available in the warm summer than the cold winter. However, summer can also be a lot more humid, so despite lots of available energy, some of the time the air doesn't have a lot of extra capacity to absorb moisture and evaporation can be slow. Still, on balance there is more potential for evaporation in summer than winter no matter where you live, even in humid climates. This is certainly true of evaporation from something like a pond where the water is in contact with the air and there is an unlimited supply of water. The situation with wood is a little different, since the water is closely held in the wood cells or intersticial spaces between wood cells, but I think wood is likely to dry better in summer, as long as you have a decent place to store it (not too damp in summer, not too shady, not tightly enclosed, etc.) Now if you happen to live in a spot where it is always calm in summer and always windy in winter, that might tip the balance, and I could probably think of some other exceptional situations, but for most of us I think summer means faster wood drying. I have not actually tested this, and i don't really pay close enough attention to say I have observed it, so this is just speculation.

Also, I don't think oak dries fast winter or summer, so my response to the original question about whether oak can go from 25 to 35% moisture content to 20% in a few weeks is I don't think so.


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## Rockey

Wood Duck said:
			
		

> Drying wood requires that water in the wood evaporates, and evaporation requires energy. There is a lot more energy available in the warm summer than the cold winter. However, summer can also be a lot more humid, so despite lots of available energy, some of the time the air doesn't have a lot of extra capacity to absorb moisture and evaporation can be slow. Still, on balance there is more potential for evaporation in summer than winter no matter where you live, even in humid climates. This is certainly true of evaporation from something like a pond where the water is in contact with the air and there is an unlimited supply of water. The situation with wood is a little different, since the water is closely held in the wood cells or intersticial spaces between wood cells, but I think wood is likely to dry better in summer, as long as you have a decent place to store it (not too damp in summer, not too shady, not tightly enclosed, etc.) Now if you happen to live in a spot where it is always calm in summer and always windy in winter, that might tip the balance, and I could probably think of some other exceptional situations, but for most of us I think summer means faster wood drying. I have not actually tested this, and i don't really pay close enough attention to say I have observed it, so this is just speculation.
> 
> Also, I don't think oak dries fast winter or summer, so my response to the original question about whether oak can go from 25 to 35% moisture content to 20% in a few weeks is I don't think so.



I'm glad someone here has their head on straight. By and large wood seasons quicker in summer. Something no one hit on is the  fact there is much more daylight during the simmer, combine that with an integration of temperature over the course of a summer day. More heat = more energy= more evaporation.


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## DBoon

This post is just begging me to go check the moisture content of my meadow drying cut, split, stacked and covered hickory after what seems to be weeks of 20-30 m.p.h. winds and subzero temperatures...

It's a long hike, but now I'm curious.  I'll reserve mention of my hypothesis until the data is in.


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## ihookem

A cup of water will dry faster in the summer than in the winter. Wood will dry faster in the summer too. I always thought wood did dry out some in winter though because it's in moisture form and not solid form. Is my head on straight too?


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## iceman

wood dries in summer and winter-------  thats the correct answer.... which one will it dry faster, --- depends on your geographical location...
personally, in my area you cant convince me wood will "season" more or less in the summer... our weather typically starts getting nice around end of may beg.. of june... it doesnt really get consistantly "hot"  until july and august...  sept is a up and down month......however thats when the air starts to become more dry....  winter is bone dry..  but it can get real cold.. so the water in the wood would freeze causing it expand, which would cause cracks and then when the temp get above freezing allow more air in the wood ... right??????   so in the end winter needs summer and summer need winter.....  unless you are somewhere that gets extreme dry heat... then of course it would dry faster sitting in dry heat and sun all day...  but over here .. we dont have tht and people up in canada do see 90 degrees that much and their winters are longer than ours....  so when does their wood season?  
i dont believe there is a right or wrong.. it just depends on YOUR location and climate on which one will get you more...... up here hot summers with high humidity isnt any good.. 60-80 degrees of dry air with a breezy summer is awesome!  a warmer winter with temps mostly in 20-40 degree range with not a lot of precip is just as good ...
all i know is around here oak needs 2+ years  which is a bummer!!
living out in ohio or the plains i am sure you guys get a lot done in the summer, its very breezy out there ...  when i  was a kid we always knew when a bad storm (tornado) was coming cause the air would get still!

 i am sure there is some formula or guide/chart we could come up with ex... 30 degrees to 80 degrees with x amount of humidity means good/bad evaporation....add in wind of x amount of mph equals ?


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## Rockey

iceman said:
			
		

> wood dries in summer and winter-------  thats the correct answer.... which one will it dry faster, --- depends on your geographical location...
> personally, in my area you cant convince me wood will "season" more or less in the summer... our weather typically starts getting nice around end of may beg.. of june... it doesnt really get consistantly "hot"  until july and august...  sept is a up and down month......however thats when the air starts to become more dry....  winter is bone dry..  but it can get real cold.. so the water in the wood would freeze causing it expand, which would cause cracks and then when the temp get above freezing allow more air in the wood ... right??????   so in the end winter needs summer and summer need winter.....  unless you are somewhere that gets extreme dry heat... then of course it would dry faster sitting in dry heat and sun all day...  but over here .. we dont have tht and people up in canada do see 90 degrees that much and their winters are longer than ours....  so when does their wood season?
> i dont believe there is a right or wrong.. it just depends on YOUR location and climate on which one will get you more...... up here hot summers with high humidity isnt any good.. 60-80 degrees of dry air with a breezy summer is awesome!  a warmer winter with temps mostly in 20-40 degree range with not a lot of precip is just as good ...
> all i know is around here oak needs 2+ years  which is a bummer!!
> living out in ohio or the plains i am sure you guys get a lot done in the summer, its very breezy out there ...  when i  was a kid we always knew when a bad storm (tornado) was coming cause the air would get still!
> 
> i am sure there is some formula or guide/chart we could come up with ex... 30 degrees to 80 degrees with x amount of humidity means good/bad evaporation....add in wind of x amount of mph equals ?



I saw that you mentioned it takes 2 years to dry oak. It takes 260 hours at 140 degrees F, 90 hours at 180 deg f, 30 hours at 220 deg F. See a trend here? The more heat you add the quicker it dries. unless Ma has lower summer time temps than winter your argument has no merit. I also saw a commment about freeze drying something. The argument here is not whether or not you can freeze dry somehting its about whether firewood seasons faster in the summer. There has been data and time spent ad nauseum to prove that more heat equals equals quicker seasoning in both lumber and firewood. until I see some documentation proving that freeze drying is quicker than adding heat then that argument is also meritless.


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## ChrisNJ

Damn good thread guys, thanks, while I enjoy both sides of the argument, here in NJ it gets awfully humid in the summer and dry in the winter, I am gonna be a chicken and agree with those that think that the year round of seasons is necessary 

Although my hands don't crack and bleed in the summer like they are now :-O


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## iceman

Rockey said:
			
		

> iceman said:
> 
> 
> 
> 
> wood dries in summer and winter-------  thats the correct answer.... which one will it dry faster, --- depends on your geographical location...
> personally, in my area you cant convince me wood will "season" more or less in the summer... our weather typically starts getting nice around end of may beg.. of june... it doesnt really get consistantly "hot"  until july and august...  sept is a up and down month......however thats when the air starts to become more dry....  winter is bone dry..  but it can get real cold.. so the water in the wood would freeze causing it expand, which would cause cracks and then when the temp get above freezing allow more air in the wood ... right??????   so in the end winter needs summer and summer need winter.....  unless you are somewhere that gets extreme dry heat... then of course it would dry faster sitting in dry heat and sun all day...  but over here .. we dont have tht and people up in canada do see 90 degrees that much and their winters are longer than ours....  so when does their wood season?
> i dont believe there is a right or wrong.. it just depends on YOUR location and climate on which one will get you more...... up here hot summers with high humidity isnt any good.. 60-80 degrees of dry air with a breezy summer is awesome!  a warmer winter with temps mostly in 20-40 degree range with not a lot of precip is just as good ...
> all i know is around here oak needs 2+ years  which is a bummer!!
> living out in ohio or the plains i am sure you guys get a lot done in the summer, its very breezy out there ...  when i  was a kid we always knew when a bad storm (tornado) was coming cause the air would get still!
> 
> i am sure there is some formula or guide/chart we could come up with ex... 30 degrees to 80 degrees with x amount of humidity means good/bad evaporation....add in wind of x amount of mph equals ?
> 
> 
> 
> 
> I saw that you mentioned it takes 2 years to dry oak. It takes 260 hours at 140 degrees F, 90 hours at 180 deg f, 30 hours at 220 deg F. See a trend here? The more heat you add the quicker it dries. unless Ma has lower summer time temps than winter your argument has no merit. I also saw a commment about freeze drying something. The argument here is not whether or not you can freeze dry somehting its about whether firewood seasons faster in the summer. There has been data and time spent ad nauseum to prove that more heat equals equals quicker seasoning in both lumber and firewood. until I see some documentation proving that freeze drying is quicker than adding heat then that argument is also meritless.
Click to expand...


it depends on location did you read that part? and you specific climate..  kiln dried would be the "perfect setup" is that what you have in your wallet/ backyard?  most people agree that you need air movement/wind... these arent in the kiln dried..   how many hours does one have at 140 in the own backyard????  if i have 40 degrees of dry air with a breeze that will not cause evaporation? .. when does wood dry  fastest???  --- it depends on YOUR specific location and climate conditions....
for you it is summer ... and maybe many others for for some it could be in the fall...  over here where i am.. our summers, when it gets real hot are just about always humid... the weather alert stay inside humid. about mid sept dry air comes in.. now there are some who live up in the mountains or people who have huge fields to maximize sun exposure but for the most part, we got a lotta trees and mountains/hills


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## Rockey

iceman said:
			
		

> Rockey said:
> 
> 
> 
> 
> 
> 
> 
> iceman said:
> 
> 
> 
> 
> wood dries in summer and winter-------  thats the correct answer.... which one will it dry faster, --- depends on your geographical location...
> personally, in my area you cant convince me wood will "season" more or less in the summer... our weather typically starts getting nice around end of may beg.. of june... it doesnt really get consistantly "hot"  until july and august...  sept is a up and down month......however thats when the air starts to become more dry....  winter is bone dry..  but it can get real cold.. so the water in the wood would freeze causing it expand, which would cause cracks and then when the temp get above freezing allow more air in the wood ... right??????   so in the end winter needs summer and summer need winter.....  unless you are somewhere that gets extreme dry heat... then of course it would dry faster sitting in dry heat and sun all day...  but over here .. we dont have tht and people up in canada do see 90 degrees that much and their winters are longer than ours....  so when does their wood season?
> i dont believe there is a right or wrong.. it just depends on YOUR location and climate on which one will get you more...... up here hot summers with high humidity isnt any good.. 60-80 degrees of dry air with a breezy summer is awesome!  a warmer winter with temps mostly in 20-40 degree range with not a lot of precip is just as good ...
> all i know is around here oak needs 2+ years  which is a bummer!!
> living out in ohio or the plains i am sure you guys get a lot done in the summer, its very breezy out there ...  when i  was a kid we always knew when a bad storm (tornado) was coming cause the air would get still!
> 
> i am sure there is some formula or guide/chart we could come up with ex... 30 degrees to 80 degrees with x amount of humidity means good/bad evaporation....add in wind of x amount of mph equals ?
> 
> 
> 
> 
> I saw that you mentioned it takes 2 years to dry oak. It takes 260 hours at 140 degrees F, 90 hours at 180 deg f, 30 hours at 220 deg F. See a trend here? The more heat you add the quicker it dries. unless Ma has lower summer time temps than winter your argument has no merit. I also saw a commment about freeze drying something. The argument here is not whether or not you can freeze dry somehting its about whether firewood seasons faster in the summer. There has been data and time spent ad nauseum to prove that more heat equals equals quicker seasoning in both lumber and firewood. until I see some documentation proving that freeze drying is quicker than adding heat then that argument is also meritless.
> 
> Click to expand...
> 
> 
> it depends on location did you read that part? and you specific climate..  kiln dried would be the "perfect setup" is that what you have in your wallet/ backyard?  most people agree that you need air movement/wind... these arent in the kiln dried..   how many hours does one have at 140 in the own backyard????  if i have 40 degrees of dry air with a breeze that will not cause evaporation? .. when does wood dry  fastest???  --- it depends on YOUR specific location and climate conditions....
> for you it is summer ... and maybe many others for for some it could be in the fall...  over here where i am.. our summers, when it gets real hot are just about always humid... the weather alert stay inside humid. about mid sept dry air comes in.. now there are some who live up in the mountains or people who have huge fields to maximize sun exposure but for the most part, we got a lotta trees and mountains/hills
Click to expand...


I can see your failing to grasp the concept here that for a given rise in temperature there is a proportionally equivalent drop in seaoning time needed. Your opinion will always be right as long as you ignore the facts. If you really believe that in YOUR location that wood dries faster in the winter than in in the summer because it is humid in the summer then you need to ask Santa Clause to bring you some kiln dried firewood, because your firewood flat out wont season as fast in the winter. I honestly think that most people with marginally seasoned wood this time of year want to convince themselves that it is seasoning faster to make themselves feel better. The others are just wrong.


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## thinkxingu

ihookem mentioned a cup of water dries more quickly in summer than in winter, but that's not the case here in Southern New Hampshire.  Case in point: in summer, if I don't use a fan in the bathroom we get tons of condensation.  In winter, I don't use one because the air is so dry it just absorbs the moisture.

So, if the air is dry, it will absorb much more moisture.  SO, what's more important dry air and wind or sun and heat?  Of course, if the water is frozen in the wood it probably won't go to far.

S


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## woodgeek

Lots of physical chemistry flying around this thread!  The answer, of course is that the evaporation rate is proportional to the difference in partial pressure of H2O.  Look up the vapor pressure of water as a fn of temp, it is about 3x higher at summer temps than winter temps.  The pressure of the water vapor in the air is that number X the relative humidity (RH).  Near the vapor source, the air is saturated (100% RH for that temp), and the difference in vapor pressure is what drives the flow of water into the ambient air.  Period.

So, that factor of 3x versus temperature can be compensated by differences in RH of outside air.  The drying RATE in winter at 40% outdoor RH, and the rate in summer at 80% RH would be about the same (60% RH difference vs 20% RH diff).   At night in most locations the RH goes to 100% as temp falls, so most drying is in the daytime (whether the sun shines on the wood or not). 

This also explains why indoor winter drying is so effective--high temp and low RH 24 hours of the day.  We should expect 3x faster rate due to high temp and low humidity, and another factor of 2x for 24 hour versus 12 hour drying.  A week inside can dry wood as well as 6 weeks of dry summer days, or maybe 8-10 weeks of actual summer weather.  Seems about right in my experience--I can (at least adequately) burn almost any wood that's been sitting in my house for two winter weeks--equiv to a full summer of outdoor seasoning.

Fact is, though, on many days no drying occurs (due to high RH during rain or snow)--how fast your wood dries during your different seasons depends on the statistics of your climate.  If you have dry summers, rainy falls and really cold/stormy winters (NE and upper midwest) you will say that most drying happens in the summer.  If you have humid/rainy summers, dry sunny falls and moderate winters (mid atlantic through lower midwest), you will find lots of drying happening in the fall and winter.


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## iceman

woodgeek said:
			
		

> Lots of physical chemistry flying around this thread!  The answer, of course is that the evaporation rate is proportional to the difference in partial pressure of H2O.  Look up the vapor pressure of water as a fn of temp, it is about 3x higher at summer temps than winter temps.  The pressure of the water vapor in the air is that number X the relative humidity (RH).  Near the vapor source, the air is saturated (100% RH for that temp), and the difference in vapor pressure is what drives the flow of water into the ambient air.  Period.
> 
> So, that factor of 3x versus temperature can be compensated by differences in RH of outside air.  The drying RATE in winter at 40% outdoor RH, and the rate in summer at 80% RH would be about the same (60% RH difference vs 20% RH diff).   At night in most locations the RH goes to 100% as temp falls, so most drying is in the daytime (whether the sun shines on the wood or not).
> 
> This also explains why indoor winter drying is so effective--high temp and low RH 24 hours of the day.  We should expect 3x faster rate due to high temp and low humidity, and another factor of 2x for 24 hour versus 12 hour drying.  A week inside can dry wood as well as 6 weeks of dry summer days, or maybe 8-10 weeks of actual summer weather.  Seems about right in my experience--I can (at least adequately) burn almost any wood that's been sitting in my house for two winter weeks--equiv to a full summer of outdoor seasoning.
> 
> Fact is, though, on many days no drying occurs (due to high RH during rain or snow)--how fast your wood dries during your different seasons depends on the statistics of your climate.  If you have dry summers, rainy falls and really cold/stormy winters (NE and upper midwest) you will say that most drying happens in the summer.  If you have humid/rainy summers, dry sunny falls and moderate winters (mid atlantic through lower midwest), you will find lots of drying happening in the fall and winter.





so in the end it depends on "the individual location, climate etc"  over where i am we get more "ideal weather for seasoning" from about mid sept on thru mid dec....  and also i would say may-june are the prime months for us.. and actually jan is good too sometimes  BUT all this is subject to change ... hell we could have a drought this summer and it would season better in the summer this year..... and get a lotta snow next year .. it always change....
at the end of the day....  wood can season in the summer (as we know) but also in the winter

rockey i dont disagree that wood will season in the summer and i don't diasagrre it will season fast given the right setup, i am simply making a case that for us over here we get can get as much  seasoning in the winter as summer because of our climate maybe more depending on the weather for the given season... if you notice the op is from southern new hampshire  which he is prolly about an hr north of me possibly in the mountains, i am in the valley so typically in the summer since we are in the "bottom are dewpoints and rh are higher


----------



## Wood Duck

thinkxingu said:
			
		

> ihookem mentioned a cup of water dries more quickly in summer than in winter, but that's not the case here in Southern New Hampshire.  Case in point: in summer, if I don't use a fan in the bathroom we get tons of condensation.  In winter, I don't use one because the air is so dry it just absorbs the moisture.
> 
> So, if the air is dry, it will absorb much more moisture.  SO, what's more important dry air and wind or sun and heat?  Of course, if the water is frozen in the wood it probably won't go to far.
> 
> S



Your bathroom fogs up in the summer because the air in the house is more or less at the same temperature as the humid outdoor air, so the relative humidity remains high indoors, and when you add a bunch of extra humidity from a hot shower, you overload the air and get condensation. On the other hand, in winter your house contain air that is much warmer than the outside air. Even though the RELATIVE humidity outside may be fairly high the ABSOLUTE humidity or moisture content is low because the cold air can't hold much moisture. When you warm up the outside air, the air's capacity to hold moisture increases dramatically and the relative humidity drops even though the absolute moisture content remains the same, or even rises. This means the indoor air can hold lots of extra moisture from the steamy shower and you don't see as much condensation. If you are attempting to season your firewood indoors in the winter, I am sure it would season fast, possibly faster than summer outdoors.

Outside right now at my place the wind is howling through the holz hausens, but at 14 degrees F I don't think there is enough energy to evaporate a lot of moisture. In this case instead of evaporating liquid water, seasoning would require sublimation of solid water directly to a vapor, which takes even more energy than evaporation of liquid.


----------



## DBoon

Just got back from checking my meadow-drying hickory.  Since November 1st, moisture content has dropped from 27% to 22%.  See this thread for more detail https://www.hearth.com/econtent/index.php/forums/viewthread/44360/

So it appears that in two months of what would be considered cold and cloudy weather, with humidity at low levels in the last month (month of December) along with below zero temperatures and very strong winds, the wood continues to dry.


----------



## Adios Pantalones

Sublimation is a slower process than evaporation.  Remember- in the winter the water is turning from ICE to vapor- not from liquid to vapor.  Also- when water leaves from surface fibers, the water in the middle is not so mobile and doesn't redistribute so quickly in ice form- but it does if it's water at warm temps.

Whether the air has a lower RH or not- the process comes to equilibrium much more quickly at a higher temp.  While the factor of the wood getting rained on is an important one, however- that cellular water getting out is more important than that extracellular water getting in, particularly for oak.

Wood dries in the winter, but much-much faster in the summer in my experience- and location.


----------



## Adios Pantalones

LOL at DBoon's avatar- "Bob Dylan wrote propaganda songs!"


----------



## DBoon

> LOL at DBoon’s avatar- “Bob Dylan wrote propaganda songs!”



Yes, that's correct Adios.  From the "What Makes a Man Start Fires" album.  Good eye.  

Just for the record, I have a lot of Bob Dylan albums also.


----------



## iceman

Adios Pantalones said:
			
		

> Sublimation is a slower process than evaporation.  Remember- in the winter the water is turning from ICE to vapor- not from liquid to vapor.  Also- when water leaves from surface fibers, the water in the middle is not so mobile and doesn't redistribute so quickly in ice form- but it does if it's water at warm temps.
> 
> Whether the air has a lower RH or not- the process comes to equilibrium much more quickly at a higher temp.  While the factor of the wood getting rained on is an important one, however- that cellular water getting out is more important than that extracellular water getting in, particularly for oak.
> 
> Wood dries in the winter, but much-much faster in the summer in my experience- and location.




this is one of those arguements that there really is no one wrong due to to many different variables, one thing we do know is wood does dry in the winter and the summer... anything after that is null n void...  without doing an experiment  of   'weather ' conditions... ie finding days of  rh with sun and breeze at 70 degrees vs i dunno 40 degrees super low rh and breezy...  i am sure if i had an open field where i got maximum sun/wind i would be on the other side....  but here i get most of mine in the fall/winter due to weather conditions .. most times... this past year we prolly all got it in fall caused it rained so much this past summer!!...


----------



## Green Energy

woodgeek said:
			
		

> The answer, of course is that the evaporation rate is proportional to the difference in partial pressure of H2O.  Look up the vapor pressure of water as a fn of temp, it is about 3x higher at summer temps than winter temps.  The pressure of the water vapor in the air is that number X the relative humidity (RH).  Near the vapor source, the air is saturated (100% RH for that temp), and the difference in vapor pressure is what drives the flow of water into the ambient air.  Period.



Woodgeek is absolutely correct that the driver for drying wood or anything is the partial pressure of H2O in the ambient air.  It is also true that when water goes from solid or liquid state to vapor, it absorbs heat.  However, it is the partial pressure of H2O that is the prime mover.  At 100 percent RH air, nothing transfers liquid (or solid) water to that air.  The reason that heat works wonders in kiln drying is that it lowers the RH of the air making the water carrying capacity of a cubic foot of air even greater.  In the summer, the dew point in my area gets into the 60s and sometimes into the lower 70s on humid summer days.  On a summer night, when the dry bulb temp equals the dew pt:  RH = 100% by definition.  At 100% RH, zero drying occurs.  However, during the day, when temps go into the 80s or 90s, RH can go down into the 50% range, upper 90s, RH that was at a 100% at 72, is now in the 30% range.  Raise the temps higher to solar drying levels or kiln levels, and the RH can approach < 5%.

Conversely, if you put anything wet in a steam room at 130 F, no drying will take place even though there is 130 F temp available. This is true because it is not temperature that determines drying rate, but partial pressure of H2O of the air, where the water goes when drying occurs.  

Generalizations about summer versus winter are always wrong, because as many people mentioned conditions vary from location to  location, AND from year to year for a given location.  Some winters around here can be 40s and rain for weeks.  When it rains, its 100% RH.  The last few days and next few days, we will have have excellently drying conditions even though the temps will be frigid because the air is soooo dry.  Also, we should have sun during the short winter days and wind.  

Just because it does take heat to vaporize H20, does not mean that there is not heat available to be absorbed at -20 F air.  There is plenty of heat available.  It is the heat that comes from lowering the temps of the surroundings from -20 to -22.  The driver is the dryness of the air, aka the partial pressure of H2O in the air.

So drying occurs both summer and winter, driven by the partial pressure of H2O in the air.  When RH reaches 100%, the air reaches its capacity for carrying any more water.  Raise the temp of that air, RH goes down; lower the temp of 100% RH air and water will condense out on surfaces below the dew point.  In my neck of the woods, we should get a lot of drying this week with frigid temps.  But not enough to dry out freshly cut oak.  As many have mentioned, bringing the wood inside, it dries even quicker, because at the higher temps in a house the RH is even lower (except for cooking, humidifiers, showers w/o exhausting air, etc. which all adds water to the air.).  If you want to get into the science and engineering of drying, a study of psychrometrics can be found at:

http://en.wikipedia.org/wiki/Psychrometrics

The psychrometric chart is used by engineers for HVAC cals of the heat and water content of air at various points in a process.


----------



## DBoon

Agreed that there are too many variables to really draw any conclusions that would be valid for everyone.  The advice I've seen often to keep it outside, covered, and in an exposed area with as much sun and wind as possible is going to dramatically speed up the seasoning and drying.


----------



## Green Energy

A dramatic example of how there is plenty of heat to evaporate water into very cold air is lake effect snow.  I just checked out the Accuweather map of lake effect snow for the Great Lakes: 12 - 18" for the southern rim of Lake Erie.  Dry air whipping across the lake drives the evaporation even when the air is frigid.  It can always find the heat to evaporate water into the dry air by simply lowering the temps of surrounds even lower.


----------



## raybonz

Judging by all the hot air in this thread I would venture to say it would dry fastest in this thread than anywhere on earth!! LOL  :ahhh: 

Ray


----------



## CrawfordCentury

Adios Pantalones said:
			
		

> Sublimation is a slower process than evaporation.  Remember- in the winter the water is turning from ICE to vapor- not from liquid to vapor.  Also- when water leaves from surface fibers, the water in the middle is not so mobile and doesn't redistribute so quickly in ice form- but it does if it's water at warm temps.
> 
> Whether the air has a lower RH or not- the process comes to equilibrium much more quickly at a higher temp.  While the factor of the wood getting rained on is an important one, however- that cellular water getting out is more important than that extracellular water getting in, particularly for oak.
> 
> Wood dries in the winter, but much-much faster in the summer in my experience- and location.



Good concise explanation, IMO.

And if you're wondering, laundry will dry at below freezing temps when hung on an outdoor line. It would take 2 to 3x as long.

Same basic principle as to why the ice cubes in my freezer from the Halloween party are some 40% smaller than when I first made them.


----------



## iceman

raybonz said:
			
		

> Judging by all the hot air in this thread I would venture to say it would dry fastest in this thread than anywhere on earth!! LOL  :ahhh:
> 
> Ray


lmao!!

after taking part of this wonderful debate...  it seems as if the conclusions is  a draw!  to many variables and due to the fact that it can dry in winter and it can dry in summer....
BUT one thing that just occured to me is my calendar was off...in my head  winter starts by thanksgiving.  around this time i am usually burning 24/7 no later than thanksgiving... so my arguement was based on in "my head" i get more/just as much   seasoning from sept -dec  than from june -august  (when our temps are there hottest)...   i wasnt thinking jan-feb-march vs june -july-august  ....  while i do believe my wood will still season,  but prolly not as much as june-july-august....  now sept-early dec yes i do believe i get more than june -august in most years of course that is subject to change according to weather!...  but this has been a great debate


----------



## raybonz

iceman said:
			
		

> raybonz said:
> 
> 
> 
> 
> Judging by all the hot air in this thread I would venture to say it would dry fastest in this thread than anywhere on earth!! LOL  :ahhh:
> 
> Ray
> 
> 
> 
> lmao!!
> 
> after taking part of this wonderful debate...  it seems as if the conclusions is  a draw!  to many variables and due to the fact that it can dry in winter and it can dry in summer....
> BUT one thing that just occured to me is my calendar was off...in my head  winter starts by thanksgiving.  around this time i am usually burning 24/7 no later than thanksgiving... so my arguement was based on in "my head" i get more/just as much   seasoning from sept -dec  than from june -august  (when our temps are there hottest)...   i wasnt thinking jan-feb-march vs june -july-august  ....  while i do believe my wood will still season,  but prolly not as much as june-july-august....  now sept-early dec yes i do believe i get more than june -august in most years of course that is subject to change according to weather!...  but this has been a great debate
Click to expand...


So true and like all debates they are full of hot air! Though wood does dry in winter it does best when the air is warm as the air being warm is able to hold that much more moisture hence the higher humidity in the summer... The saturation point of air is much higher in hot temperatures than cool temperatures... Heat will enhance evaporation in most situations and also the ability to absorb the moisture that is given off as a result... Interesting subject for sure and lots of good well thought out answers all around... This is why I love this forum however when the air warms up I tend to evaporate and condense back here when the weather cools back off!


Ray


----------



## bbc557ci

DBoon said:
			
		

> Just got back from checking my meadow-drying hickory.  Since November 1st, moisture content has dropped from 27% to 22%.  See this thread for more detail https://www.hearth.com/econtent/index.php/forums/viewthread/44360/
> 
> So it appears that in two months of what would be considered cold and cloudy weather, with humidity at low levels in the last month (month of December) along with below zero temperatures and very strong winds, the wood continues to dry.



Typical central NY guy... how dare you introduce hard evidence into this debate LMAO   

btw.... Great discussion, very interesting!!


----------



## dave11

Adios Pantalones said:
			
		

> Sublimation is a slower process than evaporation.  Remember- in the winter the water is turning from ICE to vapor- not from liquid to vapor.  Also- when water leaves from surface fibers, the water in the middle is not so mobile and doesn't redistribute so quickly in ice form- but it does if it's water at warm temps.
> 
> Whether the air has a lower RH or not- the process comes to equilibrium much more quickly at a higher temp.  While the factor of the wood getting rained on is an important one, however- that cellular water getting out is more important than that extracellular water getting in, particularly for oak.
> 
> Wood dries in the winter, but much-much faster in the summer in my experience- and location.



Exactly! That's what I tried to say with my last post, but maybe I didn't say it clearly enough.

You folks who think there is no "right answer" to this are certainly wrong.There is a right answer, and it has nothing to do with your location. Just because some other folks keep stating conflicting opinions doesn't meant there's no right answer.

Firewood has to dry faster in warmer temps than colder. If you take frozen wood, and lower the humidity around it to zero, it will not dry one bit until enough energy is absorbed from the environment to cause sublimation. Wood at 80 degrees F will dry faster than wood at 20 degrees F, no matter what the humidity is. At atmospheric pressure, which is a constant, high humidity will not impede water from leaving the wood, if there's enough energy to make it do so, and low humidity will not make it go any faster.    

It's easy to prove from every day experience. Imagine a pot of boiling water. Can you make it boil less just by covering it with a lid? You can, only if the lid is airtight and increases the pressure inside the pot. If you cover it with a loose lid, so that some steam gets out here and there, you will greatly increase the humidity over the water, but you will not make it boil any less, because it doesn't care how much water vapor is over its surface,. It only cares about the pressure, and the temperature applied. 

Same with firewood, which is exposed to a constant atmospheric pressure, but is slowly absorbing energy/heat from it's surroundings, and so, being heated, just like the water in a pot. Just much slower

Look up the values of the enthalpy of vaporization and sublimation. They are dependent only upon the atmospheric pressure, not on the partial pressure of the substance in question. Since the atmospheric pressure around the wood is constant, it's mainly the temperature that affects the rate of water evaporation. 

Wood therefore must dry much faster in warmer temps. Everywhere on earth. 

This corresponds to published data in woodworking books.


----------



## iceman

dave11 said:
			
		

> Adios Pantalones said:
> 
> 
> 
> 
> Sublimation is a slower process than evaporation.  Remember- in the winter the water is turning from ICE to vapor- not from liquid to vapor.  Also- when water leaves from surface fibers, the water in the middle is not so mobile and doesn't redistribute so quickly in ice form- but it does if it's water at warm temps.
> 
> Whether the air has a lower RH or not- the process comes to equilibrium much more quickly at a higher temp.  While the factor of the wood getting rained on is an important one, however- that cellular water getting out is more important than that extracellular water getting in, particularly for oak.
> 
> Wood dries in the winter, but much-much faster in the summer in my experience- and location.
> 
> 
> 
> 
> Exactly! That's what I tried to say with my last post, but maybe I didn't say it clearly enough.
> 
> You folks who think there is no "right answer" to this are certainly wrong.There is a right answer, and it has nothing to do with your location. Just because some other folks keep stating conflicting opinions doesn't meant there's no right answer.
> 
> Firewood has to dry faster in warmer temps than colder. If you take frozen wood, and lower the humidity around it to zero, it will not dry one bit until enough energy is absorbed from the environment to cause sublimation. Wood at 80 degrees F will dry faster than wood at 20 degrees F, no matter what the humidity is. At atmospheric pressure, which is a constant, high humidity will not impede water from leaving the wood, if there's enough energy to make it do so, and low humidity will not make it go any faster.
> 
> It's easy to prove from every day experience. Imagine a pot of boiling water. Can you make it boil less just by covering it with a lid? You can, only if the lid is airtight and increases the pressure inside the pot. If you cover it with a loose lid, so that some steam gets out here and there, you will greatly increase the humidity over the water, but you will not make it boil any less, because it doesn't care how much water vapor is over its surface,. It only cares about the pressure, and the temperature applied.
> 
> Same with firewood, which is exposed to a constant atmospheric pressure, but is slowly absorbing energy/heat from it's surroundings, and so, being heated, just like the water in a pot. Just much slower
> 
> Look up the values of the enthalpy of vaporization and sublimation. They are dependent only upon the atmospheric pressure, not on the partial pressure of the substance in question. Since the atmospheric pressure around the wood is constant, it's mainly the temperature that affects the rate of water evaporation.
> 
> Wood therefore must dry much faster in warmer temps. Everywhere on earth.
> 
> This corresponds to published data in woodworking books.
Click to expand...



The problem was.. the op asked if it dried quicker in the winter or summer.....  thats where the whole location etc... everything came in.....  some of us have real humid summers very dry breezy falls thts wht started the whole thing...  
in another post someone said his wood dries out in his house in the winter time..  and someone else pointed out it was because its warm with no humidity .. which is true... but 65 -70 degrees with  low humidity is what we get here sept -oct in july august we get hot but very humid... the weather alert to stay indoors the air is to thick.... so prime time for me inmy location is often fall-early winter not "summer" so to speak...
but it was a great deabte and wood dries year round with different variables at least that did come out of it...
cool temps will cause evaporation but that is to a certain point then you have the sublimation ...  which is slower... so  once we get steady below say 20 it really slows down... wheras if its dry in the summer no matter how high the temp goes you are still gonna have evaporation....


----------



## leaddog

It only cares about the pressure, and the temperature applied. 

Same with firewood, which is exposed to a constant atmospheric pressure, but is slowly absorbing energy/heat from it's surroundings, and so, being heated, just like the water in a pot. Just much slower

Look up the values of the enthalpy of vaporization and sublimation. They are dependent only upon the atmospheric pressure, not on the partial pressure of the substance in question. Since the atmospheric pressure around the wood is constant, it's mainly the temperature that affects the rate of water evaporation. 

Wood therefore must dry much faster in warmer temps. Everywhere on earth. 

This corresponds to published data in woodworking books.[/quote]

so does that mean that if I put my wood in a vaccum and add heat it will dry faster???????????????????
leaddog


----------



## Green Energy

dave11 said:
			
		

> Wood therefore must dry much faster in warmer temps, regardless of the humidity. Everywhere on earth.



OK, I'm may be a sucker for bait, but here goes:  I know it is counter intuitive, but heat is not nearly as important as the relative humidity.  Heat appears to be the drying agent, but only when the heat lowers the RH.  There is more heat on a 70 summer morning, than tonight (teens to 20s).  Yet in many locations in the East, overnight and in the early summer morning, the RH approaches 100% during humid weather.  If there is morning dew, then there is 100% RH at ground level.  No drying is happening on nights/mornings.  No drying is occurring when its raining, regardless of whether it's warm rain or cold rain.  This is not because that the outside of the wood can get wet, because the air is saturated with water and there is no ability to hold more water. 

When there is 100% RH, the air can not hold any more water.  No drying occurs because there is no place for the air to go.

Put a dry towel in a 130 F steam room and the towel will become wet and never dry out because the RH is at 100% even though there is plenty of heat.

The partial vapor pressure is not the same at the atmospheric pressure.  High RH correspond to high partial H20 vapor pressure, low RH correspond to low partial H2O vapor pressure.  Either condition occurs at sea level or at 10,000 ft above sea level.  Dry air is literally sucking water into it where ever water is available to it.

The prime mover of water coming out of wood, laundry, or you name it is low partial vapor pressure in the air adjacent to the surface.  Warming the air, lowers the RH/partial pressure, that why it appears that heat causes the drying.  But heat is just lowering the RH of the air.  RH of the air is what matters.

So if you want to generalize, more drying occurs during dry weather with low humidity, then during rainy weather and high humidity.

Humidity is everything when it comes to drying.


----------



## LLigetfa

I haven't seen this much junk science before.  Reminds me "Sanford and Son".

http://www.fulmersbelly.com/img/sanford.jpg

I can say my Winter dried wood actually absorbs moisture in the Summer.  Not to worry though, it will dry out again come Winter.


----------



## Green Energy

Great pic!  Way to bring the comic relief.  What does "GSD" in your signature stand for?


----------



## LLigetfa

German Shepherd Dog


----------



## Battenkiller

LLigetfa said:
			
		

> I haven't seen this much junk science before.



LMAO!

I've seen bumper stickers that say, "Honk if you passed P-Chem". I never honk. But I _do_ know that my sweaty shirt dries lots faster on hot dry days than on hot muggy days.  What's the hurry for all that moisture to evaporate?  Doesn't it know that relative humidity is irrelevant?

Enthalpy, schmenthalpy... wood dries in the winter because it's dry outside.


----------



## LLigetfa

I wonder if living in the Rainy River District has something to do with how my wood dries in Summer?  I do know that our wild temp swings in Winter here sure dries out the air.


----------



## Battenkiller

I figured out the GSD, but not the HM wife.  My wife says its the same as her's... "Her Majesty".  That true?


----------



## Bigg_Redd

Battenkiller said:
			
		

> LLigetfa said:
> 
> 
> 
> 
> I haven't seen this much junk science before.
> 
> 
> 
> 
> LMAO!
> 
> I've seen bumper stickers that say, "Honk if you passed P-Chem". I never honk. But I _do_ know that my sweaty shirt dries lots faster on hot dry days than on hot muggy days.  What's the hurry for all that moisture to evaporate?  Doesn't it know that relative humidity is irrelevant?
> 
> Enthalpy, schmenthalpy... wood dries in the winter because it's dry outside.
Click to expand...


WTF is "P-Chem"?  

I thought Chem stopped at "O"


----------



## Adios Pantalones

A- chem, O-chem, IO-chem, P-chem, biochem...

A is analytical (also called anal chem), O is organic, IO is inorganic, p-chem is physical chemistry.  

I'm not gonna get into this one anymore- there's a lot of guessing, etc.  The plural of anecdote is not data  

-pH- passed a few chemistrational classes, and took a class from Bruce Hoadley his own self.  OK- Bruce taught me to tie fishing flies, but still...


----------



## Arlo

Location Location Location... 

Here in Eastern PA its humid in the summer. At the start of the winter, half of my wood was seasoned. The other half not so seasoned. Green in fact were many pieces of re-split splits. Since November, my wood has been exposed directly to days on end of 20+mph winds. That same wood is now seasoned. I'm no scientist but I do know this, the freezing cold wind dryed my wood, possibly faster than the humid summer windless days. Like many other people have said here; "its all about location" but wood definetley dries in the winter


----------



## LLigetfa

Battenkiller said:
			
		

> I figured out the GSD, but not the HM wife.  My wife says its the same as her's... "Her Majesty".  That true?


It almost could be but it's not.  It's High Maintenance.


----------



## Battenkiller

Bigg_Redd said:
			
		

> WTF is "P-Chem"?
> 
> I thought Chem stopped at "O"



Well, my brain stopped at O-chem, but the subject itself goes on. P-chem deals with the physics of bonds and reactions and rates and thermodynamics all that stuff you just dipped into in General Chem.  Pretty heavy stuff.  I struggled with Gen Chem, breezed through O-Chem and hit a wall with P-Chem.  Has to do with the way your brain is structured I think.  Mine isn't very well structured at all.  Dropped out of chem and got a bio degree. Way, way easier.

Anyway, I won't be bullied by the physical chemistry experts into thinking my wood won't dry well in the winter, at least here in the great Northeast.  

The heat of vaporization has very little to do with the phenomenon.  _All_ water has plenty of heat from a physical chemistry point of view (until you start approaching absolute zero), even when it is frozen.  At any temperature we are likely to encounter, from -40ºF/C to 125º in the Mohave, the amount of heat in the water is vastly more than at 0º Kelvin (-460ºF, -273ºC).  Yes, the heat of vaporization goes down in a relatively linear fashion (determined by many decades of experimental data) as temperature rises, but it is still a hell of a lot at _any_ normally encountered temps.  Even at (low) internal stove temps, evaporating water robs you of massive amounts of BTUs until you get up to about 600ºF.  That's why you need to burn wet wood hot as hell.  At smoldering temps, most of the heat gained from combustion is used up just converting liquid water into water vapor, which further lowers stove temps which robs more heat, etc.  It's actually even more complicated than that, but I digress...

Water molecules enter into the air one at a time.  They can only break the strong hydrogen bonds that hold them together when they are at the very surface, or when they are converted to steam bubbles while boiling.  Yes, the hotter you get the water, the faster it will evaporate.  That's because some individual water molecules at higher temperatures are more energetically favored to overcome the heat of vaporization (which is an experimentally derived figure that is an _average_ for the entire given mass at any given temp) than are others.  Does the air in your kitchen need to be hot to evaporate a pan of water simmering away on the back of the stove?  Or more to the point, does a hot kitchen allow the water to evaporate a lot faster than a cold kitchen? No, of course not, because the energy comes from the hot water itself, not the air.  Temperature and heat are _not_ the same, and anyone throwing physical chemistry terms around should be well aware of that.  No matter how high you get the air temperature, there will always be orders of magnitude of difference between the energy contained in the two substances, with water winning the battle by a long shot... even when it is frozen.  Temperature is just a measure of molecular motion, not the amount of heat contained.  As my prof used to tell us, there is immensely more energy in a bathtub of cold water than there is in a burning match.  Case closed.

Even when winter camping, water will boil away, and at high altitudes and extreme cold it still boils and evaporates (although now at a much lower temperature).  Air temps have nothing to do with it, it's the temperature of the water itself that dictates how water turns to vapor at any given atmospheric pressure. Outside your stove (where most of us like to dry our wood), differences in the heat of vaporization at varying temps have very little to do with the drying process.  Access to the water inside the wood (by any method) to the air that surrounds it, and differences in relative humidity are what is driving the whole thing.  

Sublimation has very little to do with the process, either.  Because the relative humidity is ofter lower in the winter than in the summer in many regions, wood can dry much faster.  But if it is solid, it will have to be removed by the process of sublimation.  This, as well, has very little to do with the differences in heat of vaporization.  It is a slow process because the water molecules don't circulate around when locked into a frozen position, and because... well, there's lots less heat in frozen water.  All of the molecules that enter the vapor state must come from the very surface, the only place where they have access to the air. But freeze/thaw cycles expand wood cells and damage them, freeing up some of the water bound inside the cell and liberating it when the wood thaws out.  In the living tree, there are numerous mechanisms to stop this, or to repair the damage when it occurs, but once cut, the wood is at the mercy of the elements, which break down the fiber structure.  It has to get cold enough to really freeze the wood all the way through.  Wood is a pretty good insulator, so overnight temps in the teens just won't cut it, but let the temps drop well below 0ºF for a few days running, and you will get the effect that the old timers I knew used to call "freeze drying".  It has nothing to do with partial pressures or vacuums, and little to do with sublimation. It is mostly due to structural damage to the wood followed by low relative humidity of the winter air.  LLigetfa hit the nail on the head... wildly changing outdoor temps and conditions are what drive winter drying.  But inside a kiln, where the water in the wood itself contains more heat and, therefore, can overcome the heat of vaporization easier, the process certainly does go much quicker than it does at ambient temps.


Of course... I could be way off here.


BTW, does everybody know that wood left at a constant RH of 90% will eventually reach an equilibrium MC of about 20% at room temperature?  Just takes a lot longer.


----------



## iceman

Battenkiller said:
			
		

> Bigg_Redd said:
> 
> 
> 
> 
> WTF is "P-Chem"?
> 
> I thought Chem stopped at "O"
> 
> 
> 
> 
> Well, my brain stopped at O-chem, but the subject itself goes on. P-chem deals with the physics of bonds and reactions and rates and thermodynamics all that stuff you just dipped into in General Chem.  Pretty heavy stuff.  I struggled with Gen Chem, breezed through O-Chem and hit a wall with P-Chem.  Has to do with the way your brain is structured I think.  Mine isn't very well structured at all.  Dropped out of chem and got a bio degree. Way, way easier.
> 
> Anyway, I won't be bullied by the physical chemistry experts into thinking my wood won't dry well in the winter, at least here in the great Northeast.
> 
> The heat of vaporization has very little to do with the phenomenon.  _All_ water has plenty of heat from a physical chemistry point of view (until you start approaching absolute zero), even when it is frozen.  At any temperature we are likely to encounter, from -40ºF/C to 125º in the Mohave, the amount of heat in the water is vastly more than at 0º Kelvin (-460ºF, -273ºC).  Yes, the heat of vaporization goes down in a relatively linear fashion (determined by many decades of experimental data) as temperature rises, but it is still a hell of a lot at _any_ normally encountered temps.  Even at (low) internal stove temps, evaporating water robs you of massive amounts of BTUs until you get up to about 600ºF.  That's why you need to burn wet wood hot as hell.  At smoldering temps, most of the heat gained from combustion is used up just converting liquid water into water vapor, which further lowers stove temps which robs more heat, etc.  It's actually even more complicated than that, but I digress...
> 
> Water molecules enter into the air one at a time.  They can only break the strong hydrogen bonds that hold them together when they are at the very surface, or when they are converted to steam bubbles while boiling.  Yes, the hotter you get the water, the faster it will evaporate.  That's because some individual water molecules at higher temperatures are more energetically favored to overcome the heat of vaporization (which is an experimentally derived figure that is an _average_ for the entire given mass at any given temp) than are others.  Does the air in your kitchen need to be hot to evaporate a pan of water simmering away on the back of the stove?  Or more to the point, does a hot kitchen allow the water to evaporate a lot faster than a cold kitchen? No, of course not, because the energy comes from the hot water itself, not the air.  Temperature and heat are _not_ the same, and anyone throwing physical chemistry terms around should be well aware of that.  No matter how high you get the air temperature, there will always be orders of magnitude of difference between the energy contained in the two substances, with water winning the battle by a long shot... even when it is frozen.  Temperature is just a measure of molecular motion, not the amount of heat contained.  As my prof used to tell us, there is immensely more energy in a bathtub of cold water than there is in a burning match.  Case closed.
> 
> Even when winter camping, water will boil away, and at high altitudes and extreme cold it still boils and evaporates (although now at a much lower temperature).  Air temps have nothing to do with it, it's the temperature of the water itself that dictates how water turns to vapor at any given atmospheric pressure. Outside your stove (where most of us like to dry our wood), differences in the heat of vaporization at varying temps have very little to do with the drying process.  Access to the water inside the wood (by any method) to the air that surrounds it, and differences in relative humidity are what is driving the whole thing.
> 
> Sublimation has very little to do with the process, either.  Because the relative humidity is ofter lower in the winter than in the summer in many regions, wood can dry much faster.  But if it is solid, it will have to be removed by the process of sublimation.  This, as well, has very little to do with the differences in heat of vaporization.  It is a slow process because the water molecules don't circulate around when locked into a frozen position, and because... well, there's lots less heat in frozen water.  All of the molecules that enter the vapor state must come from the very surface, the only place where they have access to the air. But freeze/thaw cycles expand wood cells and damage them, freeing up some of the water bound inside the cell and liberating it when the wood thaws out.  In the living tree, there are numerous mechanisms to stop this, or to repair the damage when it occurs, but once cut, the wood is at the mercy of the elements, which break down the fiber structure.  It has to get cold enough to really freeze the wood all the way through.  Wood is a pretty good insulator, so overnight temps in the teens just won't cut it, but let the temps drop well below 0ºF for a few days running, and you will get the effect that the old timers I knew used to call "freeze drying".  It has nothing to do with partial pressures or vacuums, and little to do with sublimation. It is mostly due to structural damage to the wood followed by low relative humidity of the winter air.  LLigetfa hit the nail on the head... wildly changing outdoor temps and conditions are what drive winter drying.  But inside a kiln, where the water in the wood itself contains more heat and, therefore, can overcome the heat of vaporization easier, the process certainly does go much quicker than it does at ambient temps.
> 
> 
> Of course... I could be way off here.
> 
> 
> BTW, does everybody know that wood left at a constant RH of 90% will eventually reach an equilibrium MC of about 20% at room temperature?  Just takes a lot longer.
Click to expand...



my head is spinning.....  wow!....  so in conclusion are you saying that wood will dry just as much in the winter as summer as long as the temp doesnt stay below 0??


----------



## Battenkiller

iceman said:
			
		

> my head is spinning.....  wow!....  so in conclusion are you saying that wood will dry just as much in the winter as summer as long as the temp doesnt stay below 0??



_You're_ head is spinning?  I just got through writing all that. :lol: 

Not exactly.  But if you live in a climate like I do, you will get tons of drying done after several freeze/thaw cycles destroy the wood a bit.  Temps need to get above 0ºC  (but above 32ºF) for the ice to melt again. Liquid water moving to the surface of the wood can evaporate faster than the ice trapped inside the wood can evaporate by sublimation.  If the water in the wood stays frozen, is can't very easily move to the outside where it can contact the low humidity air.  All water that leaves the wood must do it at the molecular level at the air/water interface.

A good comparison is freezer burn in your home freezer.  Meat or veggies that aren't vacuum packed get pretty dried up in the low humidity of the freezer environment, but the effect is primarily limited to the outside.  Of course, as the process continues, it leaves air spaces at the surface that can then contact the water further inside.  Eventually, you might end up with a very dehydrated product, but it will take a very long time.

Best bet is to let it go all winter into the next season.  Buy or cut your wood now in the winter and go fishing in the summer like you're supposed to.  Let it get good and cracked from the freezing temps and it will dry out even better in the summer. The wood will thank you for damaging it like this, and it will reward you for your cruelty next burn season.


----------



## gerry100

Can't we get along and invoke one of those pesky laws of Thermodynamics?

If the air is drier than the wood - the wood will lose moisture no matter what time of the year it is.

If the reverse is true the wood will absorb.

The structure of the wood means that is reacts to the difference much slower than the air changes.

Therefore it eventually reaches the average moisture content of the air.

Eventually usually means 1-2 years, depending on th ewood type,shape etc.


----------



## gerry100

Can't we get along and invoke one of those pesky laws of Thermodynamics?

If the air is drier than the wood - the wood will lose moisture no matter what time of the year it is.

If the reverse is true the wood will absorb.

The structure of the wood means that is reacts to the difference much slower than the air changes.

Therefore it eventually reaches the average moisture content of the air.

Eventually usually means 1-2 years, depending on the wood type,shape etc.


----------



## ansehnlich1

ok, ok, ok, 

I admit it...

I PUT my wood in the freezer to season it  :bug:  

Naw, look, my stacks sit at the edge of a walnut grove, they get sun for a half day or more, and prevailing winds all the time. It takes 1, 2, or 3 years to season depending on species.

And YES, I think it seasons in winter as well as summer.


----------



## bogydave

With all the knowledge I just gained from seasoning wood in the Winter I've decided to only season wood in the Winter. 
I haven't figured how to stop it from seasoning in the Spring, Summer & Fall but am working on it.


----------



## Battenkiller

gerry100 said:
			
		

> If the air is drier than the wood - the wood will lose moisture no matter what time of the year it is.
> 
> If the reverse is true the wood will absorb.
> 
> 
> Therefore it eventually reaches the average moisture content of the air.



Nope.  Doesn't do that either.  Like I said, wood dried at 90% relative humidity will eventually reach a moisture content of about 20%, and it will stay that way forever as long as the RH doesn't change.  Even if you raise the RH of the surrounding air up to 100%, it won't regain much of the water it lost during seasoning. Counterintuitive... but true.


----------



## Rockey

Battenkiller said:
			
		

> gerry100 said:
> 
> 
> 
> 
> If the air is drier than the wood - the wood will lose moisture no matter what time of the year it is.
> 
> If the reverse is true the wood will absorb.
> 
> 
> Therefore it eventually reaches the average moisture content of the air.
> 
> 
> 
> 
> wood dried at 90% relative humidity will eventually reach a moisture content of about 20%, and it will stay that way forever as long as the RH doesn't change.  .
Click to expand...


There are many charts that prove this true: http://www.csgnetwork.com/emctablecalc.html

Your earlier write up was very impressive. I have a suggestion. There are guys whose livings are dpendant upon this very subject. There quite a few sawmills that cut  dimensional lumber and air dry it year round. These guys are much more practical experts on the subject than we will ever be. I think a few phone calls can give us a definitive answer. Once again I stand by my original statemnt that "by and large much more seasoning is done during the summer" If I;m wrong I;ll change my username to SisterBart or BrotherFart, take your pick, for 1 week.


----------



## awfireman

You need to use the conversion ruler to determine moisture content when its below freezing. I am in the Forestry Field and any Delhurst Moisture Reader comes the with this ruler. Oak, giving a 20% moisture reading when its 32 or below is really around 28-32% moisture depending how much you get below the freezing mark.

Fireman


----------



## woodgeek

Ok, watch out, more P-chem and partial pressure...

If I'm a water molecule in a liquid (or ice) I can hop off into the air.  While it does take a little energy for me to do that (since we are below 212°F), there is plenty of energy around--my average thermal velocity is 1000 mph.  Batten has a sensible argument.  If I'm a molecule I don't care if there are other water molecules out there when I decide to leave the liquid/ice, I only care about my energy change.

BUT the flaw in the argument is that the opposite can happen. Water molecules in the vapor can decide to rejoin the liquid/ice, and the rate of that happening is directly proportional to the ambient RH.  So, 100% RH doesn't prevent H2O molecules from leaving the liquid, it just causes the return process to balance the leaving process, for zero net drying rate.

The partial pressure concept is the easiest way to describe this.  If we put water/ice in a vacuum, it would vaporize until the total pressure of vapor suffices to return vapor to the liquid at the same rate it was leaving--equilibrium.  At 212°F, that vapor pressure is 1 ATM, which is why it forms bubbles in water at that temp on the Earth's surface. At lower temps, including below 32°F, the pressure is lower, but not zero. 

After a little googling:
T (°F)    mmHg
-40       ~0
12          2
32          5
52         10
72         15
84         30

So, this confirms that the drying rate (at 0%RH) 32°F is 1/3rd that at 72°F, or 1/6th that at 84°F.  Sounds like a lot, but is tempered by the typical lower winter RH, getting us back to the mild winter (nom 32°F) drying rate being 2-3X less than summer, but not zero.  If your typical temps in the winter are <<32°F, then yeah, your winter drying rate is the pits.

Woodworkers do know, but everything I've read about air-drying dimensional lumber is completely in line with this 2-3X rate figure.
That is: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr121.pdf
which tabulates drying time for different species and locations.  Enjoy.

Yeah--winter drying is just ok by me.


----------



## Battenkiller

Woodgeek, what you are describing with partial pressures at varying temperature is just the formal way of explaining what relative humidity is all about.  Air doesn't "hold" moisture, it's just another gas in the mix.  So all we need to know is that relative humidity is temperature dependent.  What you are saying is the same thing I'm saying, just using terms that are hard for most folks to grasp.

There is no flaw in my argument.  I never said that water molecules don't go back into the source water, just that they do so at a slower rate than they leave until equilibrium is reached.  Equilibrium is temperature dependent for sure, but it isn't only reached at 100% RH, it is reached at _any_ RH between 0% and 100%, at temps between -40ºC and 100ºC (at 760mmHg).

Even though evaporation rate is directly proportional to changes in partial pressure/relative humidity, it really doesn't matter. Wood is a very complex structure, not a drop of liquid in an enclosed flask.  The water is locked inside the structure of the wood fibers, and it's removal rate is dependent on many other things besides just the ideal gas laws.

And for the record, I never said that wood won't dry faster as temperatures rise, just that it dries a hell of a lot due to the effects of cold weather as well.  The fact that I speed dry my wet wood in my stove room (and that it actually works) is enough proof for me.

BTW, you can't really use data from air-drying dimensional lumber to explain how firewood dries.  Dimensional lumber dries mostly through the sides because its exposed surface area is almost entirely along the sides. Firewood dries mostly through the ends because it is short relative to its cross sectional area.   Makes a _big_ difference how stuff is cut.

Regardless, thanks for providing the link to the drying tables.  Good information to have no matter where or when you dry your wood. ;-)


----------



## IanDad

P Chem. Yikes! I ran away from it as fast as I could also. This thread is why I love the internet, though.

Outstanding discussion, and it certainly heartens me after a several days of 30 - 40 mph gusts and temps in the  twenties with some stacks of somewhat questionably dry wood.

Very informative. Thanks to all.


----------



## Rockey

Thank you Woodgeek. The proof is within: http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr121.pdf

Here is a direct quote from the US Department of Agriculture Forest Services -

"In addition to the effect of summer–winter temperature differences,
estimates of air drying time are affected by the time of year
when the lumber is stacked. Lumber stacked in the spring
may dry in a relatively short time because a large portion of
the drying may be in the warm spring and summer months. In
contrast, lumber stacked in late summer or early fall may take
a relatively long time to dry because it will be exposed to
winter temperatures, when drying may almost stop."

The data extrapolated from that research data graphs proves that by far in every region that they tested and for every species summer drying is FAR more effective.


----------



## Adios Pantalones

You sort of are way off on some points  .  If the water is frozen then it must sublime- so I dunno why you say "Sublimation has very little to do with the process, either. ". 

"This, as well, has very little to do with the differences in heat of vaporization. " The standard enthalpy of sublimation for a material is equivalent to the sum of its enthalpy of fusion and enthalpy of vaporization, whereas liquid water only needs to overcome vaporization.  

"you will get the effect that the old timers I knew used to call "freeze drying".  It has nothing to do with partial pressures or vacuums, and little to do with sublimation."

Water going from a solid to a vapor is sublimation.  I don't care if it's solid wood, lignum vitae, damaged balsa, or mashed potatoes.  If it's frozen, then drying is by sublimation.  Freeze drying IS sublimation.

If it's frozen, then the water has very limited mobility through the piece.  If it's cold but not frozen, then diffusion rates are also reduced.

Look- wood will dry in the winter.  If it's already dry then it may dry to a level below equilibrium that it would see in the summer, and may rehydrate a bit the next summer.  That doesn't mean that fresh wood dries faster in the winter- which is sort of the question... I think.  What the heck was the question again?




			
				Battenkiller said:
			
		

> Bigg_Redd said:
> 
> 
> 
> 
> WTF is "P-Chem"?
> 
> I thought Chem stopped at "O"
> 
> 
> 
> 
> 
> 
> Sublimation has very little to do with the process, either.  Because the relative humidity is ofter lower in the winter than in the summer in many regions, wood can dry much faster.  But if it is solid, it will have to be removed by the process of sublimation.  This, as well, has very little to do with the differences in heat of vaporization.  It is a slow process because the water molecules don't circulate around when locked into a frozen position, and because... well, there's lots less heat in frozen water.  All of the molecules that enter the vapor state must come from the very surface, the only place where they have access to the air. But freeze/thaw cycles expand wood cells and damage them, freeing up some of the water bound inside the cell and liberating it when the wood thaws out.  In the living tree, there are numerous mechanisms to stop this, or to repair the damage when it occurs, but once cut, the wood is at the mercy of the elements, which break down the fiber structure.  It has to get cold enough to really freeze the wood all the way through.  Wood is a pretty good insulator, so overnight temps in the teens just won't cut it, but let the temps drop well below 0ºF for a few days running, and you will get the effect that the old timers I knew used to call "freeze drying".  It has nothing to do with partial pressures or vacuums, and little to do with sublimation. It is mostly due to structural damage to the wood followed by low relative humidity of the winter air.  LLigetfa hit the nail on the head... wildly changing outdoor temps and conditions are what drive winter drying.  But inside a kiln, where the water in the wood itself contains more heat and, therefore, can overcome the heat of vaporization easier, the process certainly does go much quicker than it does at ambient temps.
> 
> 
> Of course... I could be way off here.
> 
> .
Click to expand...


----------



## Adios Pantalones

Rockey- Yup!  Warm weather- faster drying.  I'll stand by that- unless you happen to live where it just rains constantly I guess.


----------



## Adios Pantalones

"BTW, you can’t really use data from air-drying dimensional lumber to explain how firewood dries.  Dimensional lumber dries mostly through the sides because its exposed surface area is almost entirely along the sides. Firewood dries mostly through the ends because it is short relative to its cross sectional area.  Makes a big difference how stuff is cut."

This one has been dispelled.  I have dried enough 72" bow staves to know that it's not quite the case that the bulk of the wood dries through the ends.  See tyhe pics that someone took of split oak drying that are currently up- you can see the wet portions!


----------



## Rockey

Adios Pantalones said:
			
		

> "BTW, you can’t really use data from air-drying dimensional lumber to explain how firewood dries.  Dimensional lumber dries mostly through the sides because its exposed surface area is almost entirely along the sides. Firewood dries mostly through the ends because it is short relative to its cross sectional area.  Makes a big difference how stuff is cut."
> 
> This one has been dispelled.  I have dried enough 72" bow staves to know that it's not quite the case that the bulk of the wood dries through the ends.  See tyhe pics that someone took of split oak drying that are currently up- you can see the wet portions!



The pictures in this thread dispell it even further: https://www.hearth.com/econtent/index.php/forums/viewthread/49669/


----------



## woodgeek

Battenkiller said:
			
		

> Woodgeek, what you are describing with partial pressures at varying temperature is just the formal way of explaining what relative humidity is all about.  Air doesn't "hold" moisture, it's just another gas in the mix.  So all we need to know is that relative humidity is temperature dependent.  What you are saying is the same thing I'm saying, just using terms that are hard for most folks to grasp.
> 
> There is no flaw in my argument.  I never said that water molecules don't go back into the source water, just that they do so at a slower rate than they leave until equilibrium is reached.  Equilibrium is temperature dependent for sure, but it isn't only reached at 100% RH, it is reached at _any_ RH between 0% and 100%, at temps between -40ºC and 100ºC (at 760mmHg).
> 
> Even though evaporation rate is directly proportional to changes in partial pressure/relative humidity, it really doesn't matter. Wood is a very complex structure, not a drop of liquid in an enclosed flask.  The water is locked inside the structure of the wood fibers, and it's removal rate is dependent on many other things besides just the ideal gas laws.
> 
> And for the record, I never said that wood won't dry faster as temperatures rise, just that it dries a hell of a lot due to the effects of cold weather as well.  The fact that I speed dry my wet wood in my stove room (and that it actually works) is enough proof for me.
> 
> BTW, you can't really use data from air-drying dimensional lumber to explain how firewood dries.  Dimensional lumber dries mostly through the sides because its exposed surface area is almost entirely along the sides. Firewood dries mostly through the ends because it is short relative to its cross sectional area.   Makes a _big_ difference how stuff is cut.
> 
> Regardless, thanks for providing the link to the drying tables.  Good information to have no matter where or when you dry your wood. ;-)



Didn't mean to beat up on you, Batten, I think we are agreed about the behavior of water/ice.  I was just hopped up about all the 'energy' talk in this thread and I painted you with that brush--sorry.

Your other point is a good one: that water adsorbed in/on wood fibers is not that same as bulk water--agreed.  It will have to have a different vapor pressure vs temp.  For very hygroscopic compounds, this vapor pressure will be much lower.  While wood fiber is certainly somewhat hygroscopic, the fact that its equilibrium MC is pretty low suggests that it does not do such a great job pulling water from the air by adsorption energy--so I think using the bulk water thermodynamics is not likely to be too shabby. 

On your other point that 'transport' is the limiting factor other than partial pressure, well remember that wood is a highly porous structure with a huge specific area.  Much of the transport through the wood could be driven by (or limited by) vapor diffusion in the pore spaces.  In this limit the diffusive water flux is ALSO proportional to the (temp dependent) vapor pressure.


----------



## leaddog

Sorry guys but I just did an experment and just proved that my wood drys faster in the winter. I took a load of wood that was average of 24%. I very carefully placed it in my top compartment of my eko-80 and within 4hrs it was completely dry. This is with a outside air temp of 26* on Jan. 6. 
This has been very interesting though. It's amasing how much a person can learn here on the net.
leaddog


----------



## Battenkiller

Adios Pantalones said:
			
		

> "BTW, you can’t really use data from air-drying dimensional lumber to explain how firewood dries.  Dimensional lumber dries mostly through the sides because its exposed surface area is almost entirely along the sides. Firewood dries mostly through the ends because it is short relative to its cross sectional area.  Makes a big difference how stuff is cut."
> 
> This one has been dispelled.  I have dried enough 72" bow staves to know that it's not quite the case that the bulk of the wood dries through the ends.




I may have to throw my hands up on this one.  You keep directly quoting me, yet entirely misinterpreting what I am saying. Then you go on to tell me exactly what I have been saying all along.  All in good fun, regardless.  


72" bow staves are _not_ 16" firewood splits.  They are very long relative to their cross sectional area, and if you are drying them properly, you should be sealing the end grain anyway to avoid checking. If sealed, nearly 100% of the water lost will be by diffusion across the thickness and evaporation along the sides, with nothing lost at the ends. Go to any yard that specializes in air-dried lumber.  There will be checks in the ends that go down about 4-6" or so (unless they are sealed before stickering)  6" on both ends of a 16" firewood split is most of the whole thing.  I have several hundred board feet of air-dried northern white cedar, cherry and basswood 4/4 planks from 6-18' long that all show this end checking.  Only way to prevent it is to seal the ends or to start the drying process near the 100% RH mark in a kiln.

Picture taking slices of a round of oak on a deli slicer (we actually did this with a microtome in my botany course).  All drying will occur at the ends, and none will happen along the sides.  Regardless of what some guys think, length matters.  

On the sublimation thing, I'm not the one that is claiming that wood is drying while it's frozen.  I personally feel that it is likely that very little sublimation occurs once the outside is dry since there is very little ice at the surface to sublime.  It's the old timers I used to talk to that called it freeze drying, I'm just looking for a better explanation for the winter drying phenomenon I have experienced with stacked cord wood.  I am currently hypothesizing that drying occurs during the _thaw_ cycles, not the freezes.  I thought I have made that as obvious as possible in as many ways as I care to say it.

Anyway, all I am maintaining is that beating up firewood by exposing it to extreme cold may help it dry better later.  I never once said anywhere that wood dries faster in the cold, just that deep freezes help loosen up the free water so it can get released easier when the temps rise and RH drops. I have no scientific proof of this, but I have come to this conclusion based on many years of experience.  Your experience may be different.  LL belives his winter dried wood gets soggier in the summer, and he may be correct if his average RH is higher in the summer than in the winter.


Anyway, Adios Muchacho.  I have to go figure out why I'm getting a smoky burn today even though I'm using the driest, hardest and most thoroughly beat up wood I own. ;-)


Now... let's turn it back over to the physical chemist.  I'm really intrigued by what he is saying.  I particularly want to know why (mechanistically) there are lower vapor pressures in hydroscopic materials.  And is wood actually hydroscopic to any great degree?  Even at 100% RH, it fails to pick up much moisture once it is fully seasoned.  Seems entirely driven by RH and cohesive forces rather than the molecular attraction of water molecules to a substrate that I think of when someone uses the term hydroscopic.


----------



## iceman

what a thread
this is great!
there has to be a temp, rh%/ dewpoint/ and breeze  that is the ultimate for drying wood......
we know it dries in the summer...
we know it dries in the winter....  
which would go back to ooooooooooo
in which ever season you get the best conditions... that allow the moisture to get out.....thats when your wood will season faster....
for most it prolly will be summer for some it will be winter.. it all depends on your location AND what weather you experience during the time the wood is "seasoning"


----------



## Adios Pantalones

"72” bow staves are not 16” firewood splits."

Exactly- but they dry quickly anyway- whether the end is sealed or not (and it's not always necessary- depending on a mess of factors)- which shows that a split will dry without water going through the ends.  That's why I quoted you and disagreed- see also the pics etc alluded to earlier.

"Picture taking slices of a round of oak on a deli slicer"  OK- then the bulk of the wood's surface area is end grain- so the analogy is really not appropriate.  In a normal split- most of the area is sides.

"Now… let’s turn it back over to the physical chemist."
Well, I have a PhD in analytical chemistry- sometimes called applied physical chemistry, but as you wish.

"I particularly want to know why (mechanistically) there are lower vapor pressures in hydroscopic materials. "

It's hygroscopic, not hydroscopic (sorry- a pet peeve)- and wood comes to an equilibrium.  In fact, bow makers (for shootin' bows) will target 30-40% RH in order to achieve optimum RH in the wood.  You can set a hygrometer in a drying box or drying area, and the wood will equilibrate to 6% MC at 30%RH, and something like 9%MC at 50% RH.  This is a very reversible process without "firced drying", so the wood is not hygroscopic.  I supposeby loose definition- a wood at an MC corresponding to an RH that is lower than ambient is hygroscopic.

There are several easy treatise on what makes something hygroscopic- but essentially, the material accepts a hydration sphere that's not currently satisfied.  Add energy and you drive off water. 

"Even at 100% RH, it fails to pick up much moisture once it is fully seasoned.  Seems entirely driven by RH and cohesive forces rather than the molecular attraction of water molecules to a substrate that I think of when someone uses the term hydroscopic. "

I don't get it- you contradict yourself between the first and second sentence- is it RH or not?  Cohesive factors?  Huh?


----------



## Rockey

iceman said:
			
		

> what a thread
> this is great!
> there has to be a temp, rh%/ dewpoint/ and breeze  that is the ultimate for drying wood......
> we know it dries in the summer...
> we know it dries in the winter....
> which would go back to ooooooooooo
> in which ever season you get the best conditions... that allow the moisture to get out.....thats when your wood will season faster....
> for most it prolly will be summer for some it will be winter.. it all depends on your location AND what weather you experience during the time the wood is "seasoning"



The myth(title to this thread) has been busted. Firewood, just like lumber seasons MUCH faster in the summer than the winter in over 50 cities that were tested.


“In addition to the effect of summer–winter temperature differences,
estimates of air drying time are affected by the time of year
when the lumber is stacked. Lumber stacked in the spring
may dry in a relatively short time because a large portion of
the drying may be in the warm spring and summer months. In
contrast, lumber stacked in late summer or early fall may take
a relatively long time to dry because it will be exposed to
winter temperatures, when drying may almost stop."
- US Department of Agriculture Forest Services


----------



## Adios Pantalones

If wood dried through the ends soo much better than the sides, then we would not need to split it to dry it.


----------



## JerseyWreckDiver

My god. Junk science is one way of putting it... I've been refraining from posting lately on things like this because it seems there are some people who come here just to argue and plenty who think they can keep from being wrong just through shear insistence. Glad to see the likes of; Wood Duck, Woodgeek, Green Energy, Adios, Dave and others posting with good, provable science. (Not to mention punctuation and proper grammar...) 

What the above posters have stated can't be argued, I don't care how much you really really mean it, your wrong. Yes, the air in Winter is much much much much drier. That's because the cold air isn't capable of holding as much moisture as warm air!@#$!@$!@! 

There are some here that just won't be convinced no matter what anybody says. God himself could come down and tell them they are flat out wrong and they would just dance around it. But for those who are interested, do a search for a document from the Department of Agriculture/Forest Service/Forest Products Laboratory General Technical Report FPL-GTR-118 - Drying Hardwood Lumber.  It's a lengthy document, 144 pages. I doubt I will be able to attach it to this post but I will try. Page 39 begins the section below, this is only the first paragraph. (Sorry, this also puts the kibosh on you "it dries faster uncovered" people. There are other sections of the document that talk about winter drying and from an extensive, NATIONWIDE study, most areas in December/January etc... have only a few drying days compared to Summer months. 



Climatic Conditions
The climate of the area or region in which the hardwood air
drying yard is located greatly influences the air drying rate
and yard output. *The most influential factor is temperature*,
but RH and rainfall also play roles. In the northern United
States and most of Canada, *the drying rate is retarded during
the winter months by low temperatures*. In the southern
United States, where the winter dry-bulb temperatures are
higher, better drying conditions are expected. However, these
higher temperatures may be offset in some localities by rain
that wets the lumber and extends the drying time, unless the
lumber is well protected. Research on beech, sugar maple,
and red oak by Peck (1954, 1957, 1959) indicated that hardwoods
air dry at a moderate rate when the daily mean temperature
exceeds 45oF (7oC) and at a considerably faster rate
when the temperature exceeds 60oF (16oC).

Well, I last put wood in the Vigilant around 9:00 am, about 23f here right now and I hear a bed of coals calling to be fed. Good night all.


----------



## Battenkiller

Adios Pantalones said:
			
		

> "72” bow staves are not 16” firewood splits."
> 
> Exactly- but they dry quickly anyway- whether the end is sealed or not (and it's not always necessary- depending on a mess of factors)- which shows that a split will dry without water going through the ends.  That's why I quoted you and disagreed- see also the pics etc alluded to earlier.
> 
> "Picture taking slices of a round of oak on a deli slicer"  OK- then the bulk of the wood's surface area is end grain- so the analogy is really not appropriate.  In a normal split- most of the area is sides.
> 
> "Now… let’s turn it back over to the physical chemist."
> Well, I have a PhD in analytical chemistry- sometimes called applied physical chemistry, but as you wish.
> 
> "I particularly want to know why (mechanistically) there are lower vapor pressures in hydroscopic materials. "
> 
> It's hygroscopic, not hydroscopic (sorry- a pet peeve)- and wood comes to an equilibrium.  In fact, bow makers (for shootin' bows) will target 30-40% RH in order to achieve optimum RH in the wood.  You can set a hygrometer in a drying box or drying area, and the wood will equilibrate to 6% MC at 30%RH, and something like 9%MC at 50% RH.  This is a very reversible process without "firced drying", so the wood is not hygroscopic.  I supposeby loose definition- a wood at an MC corresponding to an RH that is lower than ambient is hygroscopic.
> 
> There are several easy treatise on what makes something hygroscopic- but essentially, the material accepts a hydration sphere that's not currently satisfied.  Add energy and you drive off water.
> 
> "Even at 100% RH, it fails to pick up much moisture once it is fully seasoned.  Seems entirely driven by RH and cohesive forces rather than the molecular attraction of water molecules to a substrate that I think of when someone uses the term hydroscopic. "
> 
> I don't get it- you contradict yourself between the first and second sentence- is it RH or not?  Cohesive factors?  Huh?




Adios, I have no idea what anyone's academic background is on a bulletin board, so don't be offended.  And for the record, just because I don't spell a word like hygroscopic correctly doesn't mean you are correct in your analysis just because you point it out.  Must I point out that you spoke of the optimum RH in the wood?  What exactly is RH in wood, and how exactly does it correlate to MC in wood and the RH of the air the wood is at equilibrium with?  


Did you really make an effort to illuminate what hygroscopic means by telling us it's a material that "accepts a hydration sphere that's not currently satisfied"?  I never implied that I have any advanced chemistry in my background.  My understanding is simply that of a lay person smitten with curiosity, so bear with me, eh?  When I am pressed to describe what is going on in a piece of wood, I use terms that I feel are correct, even though they may not be.   I know water molecules have a strong attraction to each other because they are highly polar molecules.  I thought that on a macro scale, that was called cohesion.  The term has been used in the literature to describe why water can stay up way above 32 feet even after transpiration stops.  I believe that capillary action is a cohesive force, but feel free to correct me if I am wrong.



The water in wet wood leaves the end grain primarily through the tubules that run longitudinally within it.  The shorter you cut it, the faster it will leave the wood.


It makes sense to me that water will be drawn along the tubules via capillary action, so when some disappears at the ends, more will be drawn along to replace it.  If that has nothing to do with cohesion, then simply correct me, don't accuse me of contradicting myself. When I said, “Even at 100% RH, it fails to pick up much moisture once it is fully seasoned.  Seems entirely driven by RH and cohesive forces rather than the molecular attraction of water molecules to a substrate that I think of when someone uses the term hydroscopic.", I was replying to another poster who was speaking of wood being hygroscopic to some degree.  I felt that there were other forces that were at play that were responsible for the re-uptake of water into wood, and that even at 100% RH, wood failed to continue to attract water molecules past the point of equilibrium as a truly hygroscopic material would.  Therefore, the entire rehydration process had to do with RH alone, and water's strong affinity for itself keeps it from continuing to dry out past equilibrium.   Maybe not a solid scientific explanation, but hey, I'm not submitting my posts here for peer review. 


The water in wet wood leaves the faces primarily by the process of diffusion across the grain. The thinner you split it, the faster it leave the wood.  


I cut guitar wood to about 3/16".  The pieces are about 24" long and about 9" across.  Cut that way like a veneer, they dry so fast through the faces that they never check at the ends.  But if I left them in split wedges, they would be useless inside a couple of days because the checks formed at the ends would propagate even after the wood was cut into slices.  That's why it is necessary to seal the ends thoroughly if they are left in large splits.



You don't need to have an analytical physical chemist tell you that wood dries through the faces as well as through the end grain.  Anyone who has split green wood for kindling knows it will be dry as a bone in a day or two inside the stove room.  I don't think anyone believes that the air sucks it all out of the end grain like a drinking straw. 

All I am saying is that the _free water_, water that is not bound to the cellular structure of the wood fibers themselves, leaves a _lot_ faster than it does through the faces in most species of wood, but the _ratio_ of drying between the two surfaces depends on how the wood is cut.  It's not just about the relative sizes of the surface areas. Wood is not homogenous in structure. That's why checks form at the ends, even in long boards.


Anyway, aside from all this... I'm interested in the bows you make.  You mentioned Tonkin cane on another thread.  Are they laminated?  Any links so we can see them?


----------



## skyline

I came here looking for more ideas for improving my wood storage but this has been a fun read and I just can't resist jumping in. 

Some observations:

We all have trouble being persuaded on anything that is counter to our experiences especially when we think we know why they happen, me included, Rockey too! :coolsmile: 

From my background I will stand firmly in the camp that the Relative Humidity(RH) gradient between the wood and surrounding air PRIMARILY drives the drying process, not temperature, but yes since RH is related to temperature, it is also a factor but less relevant regarding what has been posted and less important as several have explained. 
If my physics, climate and hydrology classes hadn't taught me that, living in Virginia in the summer and Nevada in the winter certainly has.

But don't take just my word for it, check out http://www.woodweb.com/knowledge_base/Wood_Handbook.html for the most authoritative discussion on wood properties.
To quote the "Wood Handbook" often considered to be the wood workers bible,
"The rate at which moisture moves in wood depends on the relative humidity of the surrounding air, the steepness of the moisture gradient, and the temperature of the wood. The lower the relative humidity, the greater the capillary flow. Low relative humidity also stimulates diffusion by lowering the moisture content at the surface, thereby steepening the moisture gradient and increasing the diffusion rate. The greater the temperature of the wood, the faster moisture will move from the wetter interior to the drier surface.

So everyone deserves some credit but RH is the driving factor.

Rockey may be correct in that in "most" places of the U.S. for us wood burners, there is an advantage in summer drying over winter, but if you mistakenly think it's primarily temperature driven and not RH it won't necessarily help you with your wood storage design, drying techniques and how best to take advantage of winter's low relative humidity and those things are ultimately why many of us are here. And while others have correctly pointed out, that it depends upon where you are. See Table 12–1."Equilibrium moisture content of wood, exposed to outdoor atmosphere, in several U.S. locations" 
in 1997 in Wood Handbook, often there is negligible difference between summer and winter in natural outdoor conditions and most of us are trying to modify those by covering our wood, sheds etc.

The original question (I think :-S) about drying faster or slower in summer or winter that morphed into why or how fast our wood dries in winter may not be the right question. The wood will dry the fastest when it is the wettest and the RH is the lowest. RH being the same it will dry faster at higher temps. Just like the temperature of our hot coffee cools the fastest at first (when the gradient is highest), the wood will lose its moisture the fastest when its first cut and split and the gradient is likely to be the highest and gradually slow down from there.  This is like every other steep gradient we experience whether it be temperature, humidity, speed etc. 

We probably don't compare this often as I suspect most of us cut and split our wood when the weather is nice, when our wood is the wettest and will therefore dry the fastest. But I recommend everyone buy an extra scale and take it to your wood shed. Weigh a few fresh rounds, split them and tie the pieces back together (bark to bark) and re-weigh them everyday and watch how fast the weight decrease at first and then more slowly after that no matter the temperature. Put one round on the pile, the wind, the garage and see what works best in your location and season and share the data. 

Below freezing temperatures, wood species, cell structure also play a role. I had a shear splitter once and the wood dried faster than when saw cut when tested due to the wood fibers being torn instead of cut. 

For me, I'm hoping for a wood shed that keeps the wood dry, slightly raises the temperature above to ambient to lower the RH,(perhaps solar) and a fan or wind exposure to maximize drying speed. If you have some good ideas pleas pass them on.

Just my two cents.


----------



## woodgeek

Battenkiller said:
			
		

> Now... let's turn it back over to the physical chemist.  I'm really intrigued by what he is saying.  I particularly want to know why (mechanistically) there are lower vapor pressures *in* hydroscopic materials.  And is wood actually hydroscopic to any great degree?  Even at 100% RH, it fails to pick up much moisture once it is fully seasoned.  Seems entirely driven by RH and cohesive forces rather than the molecular attraction of water molecules to a substrate that I think of when someone uses the term hydroscopic.



I am giving you a prop on the whole wood adsorbed water is not the same as bulk water issue.  I wouldn't use "in" here, so much as "in contact with".  The idea is that near the interface between the air and the liquid/solid water the RH is locally 100%, or in equilibrium (by definition), because the two phases are in intimate contact.  If a solid material is hygroscopic, there is a binding energy that favors the water to be in/on the solid (moreso than in a bulk liquid) and that will shift the equilibrium partial pressure below the bulk water/vapor equilibrium partial pressure.  

If wood retains finite MC at less that 100% ambient RH in equilibrium (e.g. as Adios points out), then it is by the above definition somewhat hygroscopic.  If there were no binding energy it would dry out completely (eventually).  So, the vapor pressure of water in the pore spaces of the wood (and presumably the rate of drying) is lower than suggested by the bulk water tables.  If there were a temp dependence to this effect, I would expect that it would be more important at lower temp, making winter even less favorable at low temps than the 2-3X slower rate predicted by the bulk water vapor pressure table.  That is, hygroscopic things work better at absorbing at low temps (which is why you dry silica gel in an oven to regenerate it).

On everything stopping below 32F: The pore water will freeze into ice at 32F, but it will still sublime at the previously liquid/vapor interfaces. The vapor/ice partial pressure at 31F and the vapor/liquid pp at 33F are basically the same, so the drying rate of pore water should not change by much on freezing. Moreover, the adsorbed water isn't ice below 32F, its still adsorbed water.  The water molecules are touching the wood, not each other, and so can't form an ice crystal.  There is no reason why their mobility or vapor pressure should do anything special at 32F either.  I get your water crystals breaking the the structure thing, which is intriguing, but do you have any evidence?  Can't wood fibers be stretchy enough to accommodate the strain?

On the end/side drying issue--I think we all know that split wood dries faster, so there must be some drying out the sides.  I saw a study once (can't find it) that said the diffusivity of water is 4x higher along the grain than across it, so a drying front would move in from the ends 2x faster than from the sides (its a square root of D).  Not a huge difference.  The cracking ends are due to the shrinkage being across the grain rather than along it (as lots of folks here will confirm). So, once the wood piece is more than couple times longer than it is wide, that guy will dry as much through the sides as the ends.  That square root business also explains why a 'plank' that is much thinner in one cross grain direction dries so much faster than a square cross section--splitting a square into two planks should dry 4x faster, into 3 equal planks should dry 9x faster etc.

Sorry to those who hate long posts....


----------



## iceman

Rockey said:
			
		

> iceman said:
> 
> 
> 
> 
> what a thread
> this is great!
> there has to be a temp, rh%/ dewpoint/ and breeze  that is the ultimate for drying wood......
> we know it dries in the summer...
> we know it dries in the winter....
> which would go back to ooooooooooo
> in which ever season you get the best conditions... that allow the moisture to get out.....thats when your wood will season faster....
> for most it prolly will be summer for some it will be winter.. it all depends on your location AND what weather you experience during the time the wood is "seasoning"
> 
> 
> 
> 
> The myth(title to this thread) has been busted. Firewood, just like lumber seasons MUCH faster in the summer than the winter in over 50 cities that were tested.
> 
> 
> “In addition to the effect of summer–winter temperature differences,
> estimates of air drying time are affected by the time of year
> when the lumber is stacked. Lumber stacked in the spring
> may dry in a relatively short time because a large portion of
> the drying may be in the warm spring and summer months. In
> contrast, lumber stacked in late summer or early fall may take
> a relatively long time to dry because it will be exposed to
> winter temperatures, when drying may almost stop."
> - US Department of Agriculture Forest Services
Click to expand...



the myth isnt busted until "we" do the experiment and make a video!

so how bout we all split some wood and report back with mc,  say over a 4 month period and we can all give - species of the wood our location and we can track it... then we can really see who has the shortest drying time.. as well as see how other fare in other parts of the country.....
anyone on board?


----------



## Adios Pantalones

"And for the record, just because I don’t spell a word like hygroscopic correctly doesn’t mean you are correct in your analysis just because you point it out."

Notice that I called it a pet peeve.  The spelling is  a common misunderstaning    I didn't state or imply that your use of it proved or disproved anything- just that it crossed my own neurosis.  

Other than that I'll just say that everyone's observation is that wood split thinner dries much quicker- by a huge factor.  That tells us that water is leaving the sides at a greater rate than the ends.  I have had rounds sit and not dry a lick in a year (have had them gush out free water), but when split they dry lickedy split (pun intended).  If end grain was the primary route of drying then wood would dry about as quick in log form.  As I pointed out- long pieces (with relatively low end grain area per mass) dry MUCH quicker than an 18" round- therefore It's pretty easy to conclude that through the sides is the primary route of drying for wood that we actually burn (not super thin cross sections).


----------



## Wood Duck

The diverse and sometimes scientific theoretical points of view posted here indicate to me that drying of firewood is a process that is best quantified empirically. In other words, you have to measure moisture content in real firewood to know how fast it seasons. There are just too many variables and too many assumptions are necessary to apply theory to firewood seasoning. We have all done the experiment, but haven't collected the data. As I sit here, I am thinking it wouldn't be that tough to conduct my own wood seasoning experiment; in fact I am conducting one in the back yard right now, but I know I'll never bother to collect data.


----------



## JerseyWreckDiver

skyline said:
			
		

> I came here looking for more ideas for improving my wood storage but this has been a fun read and I just can't resist jumping in.
> 
> Some observations:
> 
> We all have trouble being persuaded on anything that is counter to our experiences especially when we think we know why they happen, me included, Rockey too! :coolsmile:
> 
> From my background I will stand firmly in the camp that the Relative Humidity(RH) gradient between the wood and surrounding air PRIMARILY drives the drying process, not temperature, but yes since RH is related to temperature, it is also a factor but less relevant regarding what has been posted and less important as several have explained.
> If my physics, climate and hydrology classes hadn't taught me that, living in Virginia in the summer and Nevada in the winter certainly has.
> 
> But don't take just my word for it, check out http://www.woodweb.com/knowledge_base/Wood_Handbook.html for the most authoritative discussion on wood properties.
> To quote the "Wood Handbook" often considered to be the wood workers bible,
> "The rate at which moisture moves in wood depends on the relative humidity of the surrounding air, the steepness of the moisture gradient, and the temperature of the wood. The lower the relative humidity, the greater the capillary flow. Low relative humidity also stimulates diffusion by lowering the moisture content at the surface, thereby steepening the moisture gradient and increasing the diffusion rate. The greater the temperature of the wood, the faster moisture will move from the wetter interior to the drier surface.
> 
> So everyone deserves some credit but RH is the driving factor.
> 
> Rockey may be correct in that in "most" places of the U.S. for us wood burners, there is an advantage in summer drying over winter, but if you mistakenly think it's primarily temperature driven and not RH it won't necessarily help you with your wood storage design, drying techniques and how best to take advantage of winter's low relative humidity and those things are ultimately why many of us are here. And while others have correctly pointed out, that it depends upon where you are. See Table 12–1."Equilibrium moisture content of wood, exposed to outdoor atmosphere, in several U.S. locations"
> in 1997 in Wood Handbook, often there is negligible difference between summer and winter in natural outdoor conditions and most of us are trying to modify those by covering our wood, sheds etc.
> 
> The original question (I think :-S) about drying faster or slower in summer or winter that morphed into why or how fast our wood dries in winter may not be the right question. The wood will dry the fastest when it is the wettest and the RH is the lowest. RH being the same it will dry faster at higher temps. Just like the temperature of our hot coffee cools the fastest at first (when the gradient is highest), the wood will lose its moisture the fastest when its first cut and split and the gradient is likely to be the highest and gradually slow down from there.  This is like every other steep gradient we experience whether it be temperature, humidity, speed etc.
> 
> We probably don't compare this often as I suspect most of us cut and split our wood when the weather is nice, when our wood is the wettest and will therefore dry the fastest. But I recommend everyone buy an extra scale and take it to your wood shed. Weigh a few fresh rounds, split them and tie the pieces back together (bark to bark) and re-weigh them everyday and watch how fast the weight decrease at first and then more slowly after that no matter the temperature. Put one round on the pile, the wind, the garage and see what works best in your location and season and share the data.
> 
> Below freezing temperatures, wood species, cell structure also play a role. I had a shear splitter once and the wood dried faster than when saw cut when tested due to the wood fibers being torn instead of cut.
> 
> For me, I'm hoping for a wood shed that keeps the wood dry, slightly raises the temperature above to ambient to lower the RH,(perhaps solar) and a fan or wind exposure to maximize drying speed. If you have some good ideas pleas pass them on.
> 
> Just my two cents.



Skyline, the document you are suggesting as support of your position is contradicting you.
From pg. 12-6. 

Air Drying
The main purpose of air drying lumber is to evaporate as
much of the water as possible before end use or transfer to a
dry kiln. Air drying usually extends until wood moisture
content is as low as 20% to 25%, at which time the lumber
is transferred to a dry kiln if final drying to a lower moisture
content is required. Sometimes, depending on a mill’s
scheduling, air drying may be cut short at a higher moisture
content before the wood is sent to the dry kiln. Air drying
saves energy costs and reduces required dry kiln capacity.
Limitations of air drying are generally associated with uncontrolled
drying.* The drying rate is very slow during the cold
winter months.*

Interestingly this is another Forest Service Document which is mostly a compilation of many others including the more detailed one I referenced above...

There is no question, RH is a major player in the drying process, but think about it, what drives RH more then anything else???? TEMPERATURE!


My 0.02 - worth the price charged.


----------



## Rockey

iceman said:
			
		

> Rockey said:
> 
> 
> 
> 
> 
> 
> 
> iceman said:
> 
> 
> 
> 
> what a thread
> this is great!
> there has to be a temp, rh%/ dewpoint/ and breeze  that is the ultimate for drying wood......
> we know it dries in the summer...
> we know it dries in the winter....
> which would go back to ooooooooooo
> in which ever season you get the best conditions... that allow the moisture to get out.....thats when your wood will season faster....
> for most it prolly will be summer for some it will be winter.. it all depends on your location AND what weather you experience during the time the wood is "seasoning"
> 
> 
> 
> 
> The myth(title to this thread) has been busted. Firewood, just like lumber seasons MUCH faster in the summer than the winter in over 50 cities that were tested.
> 
> 
> “In addition to the effect of summer–winter temperature differences,
> estimates of air drying time are affected by the time of year
> when the lumber is stacked. Lumber stacked in the spring
> may dry in a relatively short time because a large portion of
> the drying may be in the warm spring and summer months. In
> contrast, lumber stacked in late summer or early fall may take
> a relatively long time to dry because it will be exposed to
> winter temperatures, when drying may almost stop."
> - US Department of Agriculture Forest Services
> 
> Click to expand...
> 
> 
> 
> the myth isnt busted until "we" do the experiment and make a video!
> 
> so how bout we all split some wood and report back with mc,  say over a 4 month period and we can all give - species of the wood our location and we can track it... then we can really see who has the shortest drying time.. as well as see how other fare in other parts of the country.....
> anyone on board?
Click to expand...



Darnit, I was hoping we could open a "busted" section and this could be the first topic


----------



## iceman

Rockey said:
			
		

> iceman said:
> 
> 
> 
> 
> 
> 
> 
> Rockey said:
> 
> 
> 
> 
> 
> 
> 
> iceman said:
> 
> 
> 
> 
> what a thread
> this is great!
> there has to be a temp, rh%/ dewpoint/ and breeze  that is the ultimate for drying wood......
> we know it dries in the summer...
> we know it dries in the winter....
> which would go back to ooooooooooo
> in which ever season you get the best conditions... that allow the moisture to get out.....thats when your wood will season faster....
> for most it prolly will be summer for some it will be winter.. it all depends on your location AND what weather you experience during the time the wood is "seasoning"
> 
> 
> 
> 
> The myth(title to this thread) has been busted. Firewood, just like lumber seasons MUCH faster in the summer than the winter in over 50 cities that were tested.
> 
> 
> “In addition to the effect of summer–winter temperature differences,
> estimates of air drying time are affected by the time of year
> when the lumber is stacked. Lumber stacked in the spring
> may dry in a relatively short time because a large portion of
> the drying may be in the warm spring and summer months. In
> contrast, lumber stacked in late summer or early fall may take
> a relatively long time to dry because it will be exposed to
> winter temperatures, when drying may almost stop."
> - US Department of Agriculture Forest Services
> 
> Click to expand...
> 
> 
> 
> the myth isnt busted until "we" do the experiment and make a video!
> 
> so how bout we all split some wood and report back with mc,  say over a 4 month period and we can all give - species of the wood our location and we can track it... then we can really see who has the shortest drying time.. as well as see how other fare in other parts of the country.....
> anyone on board?
> 
> Click to expand...
> 
> 
> 
> Darnit, I was hoping we could open a "busted" section and this could be the first topic
Click to expand...


well,,.... we could always start a new thread !


----------



## Battenkiller

After reading how much some of you have invested in your wood burning operations, maybe we can start a "flat busted" thread.

Anybody got a photo of Keira Knightly?


----------



## Rockey

Battenkiller said:
			
		

> After reading how much some of you have invested in your wood burning operations, maybe we can start a "flat busted" thread.
> 
> Anybody got a photo of Keira Knightly?



I saw a picture earlier today of Sarah Palin when she was younger wearing a shirt that said "I may be broke but Im not flat busted"


----------



## skyline

Skyline, the document you are suggesting as support of your position is contradicting you.
From pg. 12-6. 

Air Drying
The main purpose of air drying lumber is to evaporate as
much of the water as possible before end use or transfer to a
dry kiln. Air drying usually extends until wood moisture
content is as low as 20% to 25%, at which time the lumber
is transferred to a dry kiln if final drying to a lower moisture
content is required. Sometimes, depending on a mill’s
scheduling, air drying may be cut short at a higher moisture
content before the wood is sent to the dry kiln. Air drying
saves energy costs and reduces required dry kiln capacity.
Limitations of air drying are generally associated with uncontrolled
drying.* The drying rate is very slow during the cold
winter months.*

Interestingly this is another Forest Service Document which is mostly a compilation of many others including the more detailed one I referenced above...

There is no question, RH is a major player in the drying process, but think about it, what drives RH more then anything else???? TEMPERATURE!


My 0.02 - worth the price charged.[/quote]

Jerseywreckdiver,

No, the document doesn't contradict me, you do.
Here's the difference.  What I quoted directly addresses RH as the driving force, as well as addressing temperature. To be redundant:

The rate at which moisture moves in wood depends on the relative humidity of the surrounding air, the steepness of the moisture gradient, and the temperature of the wood. The lower the relative humidity, the greater the capillary flow. Low relative humidity also stimulates diffusion by lowering the moisture content at the surface, thereby steepening the moisture gradient and increasing the diffusion rate. The greater the temperature of the wood, the faster moisture will move from the wetter interior to the drier surface.

What you've quoted doesn't even mention RH, but you have gone on to ASSUme that temperature is the primary factor since you read "the drying rate is very slow during the cold
winter months."

As I stated before, Rockey was correct in that in most areas of the U.S. wood dries faster in summer than winter. No surprise as the Equilibrium Moisture Content is lower in the summer in most places (SE exceptions)

The science of kiln drying lumber generally boils down to controlling the RH around the wood so that it doesn't dry too fast and check, crack, warp etc. Temperature is often used to speed the process as expected for economic reasons. The goal being to get wood to a state of moisture content close to it's eventual RH environment (regardless of temperature) so that it performs well.

To quote you "think about it" Why are fans used in kilns regardless of their operating temperatures. To keep the RH at the wood/air interface from becoming saturated so that it continues to dry.
There's no quicker way to become fired as a kiln operator than to ignore RH. Yes, we all know RH is related to temperature but functionally important for all of us wood burners is how best to dry our wood and know that we can continue to dry our wood in winter especially if we can take advantage of lower RH conditions. 

Few of us have the means to provide summer time temperatures for our wood stacks in winter but we can do lots do reduce RH, such as dry storage, elevated off the ground, increased air movement around pile and even a slight temperature increase over the ambient to reduce RH.

I match your .02 cents and call!


----------



## skyline

I hate to post after my post but I think I have found better data to answer some of what we have been discussing, certainly not all.

So addressing the question, (and only this question!) which is more important, temperature or Relative Humidity in drying our firewood

Again, according to Wood Handbook http://www.woodweb.com/knowledge_base/Wood_Handbook.html
See specifically chapter 3 pg 5 & 7

"The Equilibrium Moisture Content
The moisture content of wood below the fiber saturation point is a function of both relative humidity and temperature of the surrounding air. Equilibrium moisture content (EMC) is defined as that moisture content at which the wood is neither gaining nor losing moisture; an equilibrium condition has been reached. The relationship between EMC, relative humidity, and temperature is shown in Table 3–4. For most practical purposes, the values in Table 3–4 may be applied to wood of any species."

So when wood reaches it's EMC conditions it will be happy. Until then it will try to lose (or gain) moisture to match the EMC conditions outside.
The lower the EMC conditions we provide the steeper the gradient and the faster the wood will try to get there.

I'll try to reproduce the table here but you may have to check it out for yourselves

Table 3–4. Moisture content of wood in equilibrium with stated temperature and relative humidity 
Temperature Moisture content (%) at various relative humidity values 
(°C    (°F)) 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% 55%   60% 65% 70% 75% 80% 85% 90% 95% 
−1.1  (30) 1.4  2.6   3.7   4.6   5.5   6.3   7.1   7.9   8.7   9.5   10.4   11.3 12.4 13.5 14.9 16.5   18.5 21.0 24.3 
4.4    (40) 1.4  2.6   3.7   4.6   5.5   6.3   7.1   7.9   8.7   9.5   10.4   11.3 12.3 13.5 14.9 16.5   18.5 21.0 24.3 
10.0  (50) 1.4  2.6   3.6   4.6   5.5   6.3   7.1   7.9   8.7   9.5   10.3   11.2 12.3 13.4 14.8 16.4   18.4 20.9 24.3 
15.6  (60) 1.3  2.5   3.6   4.6   5.4   6.2   7.0   7.8   8.6   9.4   10.2   11.1 12.1 13.3 14.6 16.2   18.2 20.7 24.1 
21.1  (70) 1.3  2.5   3.5   4.5   5.4   6.2   6.9   7.7   8.5   9.2   10.1   11.0 12.0 13.1 14.4 16.0   17.9 20.5 23.9 
26.7  (80) 1.3  2.4   3.5   4.4   5.3   6.1   6.8   7.6   8.3   9.1     9.9   10.8 11.7 12.9 14.2 15.7   17.7 20.2 23.6 
32.2 (90) 1.2   2.3   3.4   4.3   5.1   5.9   6.7   7.4   8.1   8.9     9.7   10.5 11.5 12.6 13.9 15.4   17.3 19.8 23.3 
37.8 (100) 1.2 2.3   3.3   4.2   5.0   5.8   6.5   7.2   7.9   8.7     9.5   10.3 11.2 12.3 13.6 15.1   17.0 19.5 22.9 
43.3 (110) 1.1 2.2 3.2 4.0 4.9 5.6 6.3 7.0 7.7 8.4 9.2 10.0 11.0 12.0 13.2 14.7 16.6 19.1 22.4 
48.9 (120) 1.1 2.1 3.0 3.9 4.7 5.4 6.1 6.8 7.5 8.2 8.9 9.7 10.6 11.7 12.9 14.4 16.2 18.6 22.0 

As expected, higher temperatures have lower EMC as do lower RH. If I wanted to know which was more important in drying my wood, RH or Temperature I might ask which is going to drive my EMC lower, raising the temperature 30 °F or lowering RH 30%. Example: from 40 °F to 70 °F or 70% RH to 40% RH. (realistic values for our discussion) 
From the table, wood EMC will decrease between .1 and .5 across RH's between 5% and 80% when raising the temperature by 30 °F.

If on the other hand one lowers the RH from 70% to 40% the EMC drops between 5.6 (13.5 to 7.9)  at 40 °F to 5.4 (13.1 to 7.7)  at 70 °F.
This shows a 30% RH change is about 50X more significant in changing the EMC of wood (the point at which wood doesn't want to release or gain moisture) than changing the temperature by 30 °F 
Incidentally lowering the RH it is more affective at lower temperatures than higher!

Yes °C are larger degrees than °F but still insignificant compared to RH.

So how does this translate for us. Effort spent of lowering the RH around our wood piles is more important than raising the temperature unless that also lowers the RH.
What are the best ways to do that? That's what I came here for in the first place

I think I want to take back my last hand, match your .02 cent and raise it a quarter.


----------



## Adios Pantalones

Skyline- that doesn't really address the question- which is- does it dry faster in the winter.  It only addresses - does it dry more.  

The wood will be at a lower EMC, but it could take forever to get there- so it doesn't address the debate I think.

what was the question again?


----------



## skyline

No it only address the question I said it addressed.
"... which is more important, temperature or Relative Humidity in drying our firewood."

As stated in previous posts, the data  http://www.woodweb.com/knowledge_base/Wood_Handbook.html Chapt. 12 pg 4 shows in general,  Lower EMC values in "more" places of the U.S. during the summer, thus wood generally dries faster in the summer with no input on our part. This is more pronounced in the arid west than new england.
But for example Boston's lowest EMC month is February, New York's is April, you throw in local variables of wind and moisture supply and we're back to that old statement for your wood pile, it depends on where you are.
But the main reason it depends on where you are is because RH is more important in adjusting the EMC conditions than temperature!

And besides these differences between the EMC across seasons are generally small and we can affect those if we know what to do work on, ie. prioritise RH over temperature.

My Final Answer, I hope!


----------



## Lumber-Jack

Well this thread probably has some of the most detailed, thought out, researched and convincing information I think I have ever read in this forum, but certainly the most convincing argument was made by Bigg_Redd in his post way back on the first page of the thread. Notice the way he actually took the trouble to spell out the word "period" instead of just hitting the period key. This in itself demonstrations his certainty and conviction in his answer, and as if that wasn't testimony enough, finalizing his post with the statement "The End", surely that alone should have precluded any further discussion or debate on the matter.

No, Redd had me convinced long ago.........   Period, The End




			
				Bigg_Redd said:
			
		

> Of course regional particulars vary, but, all things being equal wood will dry faster the warmer it is.
> 
> Period.
> 
> The End.


----------



## skyline

I know (hope) you answer in jest, but this is why data only goes so far. 
No matter the results of  people believe what they want to, and when they don't have any data, they ignore it or make some up.

The fact the data shows Relative Humidity 50 X more important to lowering wood's EMC than temperature, is significant. 
It means lots of other variables can probably be safely discounted as they won't overcome such a huge relative difference.

Of course what Bigg_Redd said is true "...all things being equal(including Relative Humidity) wood will dry faster the warmer it is.  

Equally true and more important ...."all things being equal(including temperature) wood will dry faster the lower the RH. 

Double Period..


----------



## Adios Pantalones

"No it only address the question I said it addressed.
“... which is more important, temperature or Relative Humidity in drying our firewood.”"

No, it only addresses how much moisture, not how fast in the winter, which is part of that question, and the entire topic of this thread. 


LOL- sorry- there I go trying to get on-topic


----------



## dave11

If the arguments made from an energy consumption standpoint still don't sway everybody, then I think the Forestry study already mentioned, and the numerous trade publication statements should settle the issue. *Wood dries faster in the summer than the winter*. If you need yet another reference, here's another from Missouri Dept of Agriculture:

http://extension.missouri.edu/publications/DisplayPub.aspx?P=G5550

Also, some people here are continuing to confuse the concept of Relative Humidity in the air around the wood with the moisture content of the air. They are not the same. Just because the RH is 80% doesn't mean the wood will eventually reach an MC of 80%. A RH of 80% will ultimately lead to a MC in the wood of 16%. In other words, you can get wood perfectly dry, in the woodburner's sense, even if you live in an area with constant 80% RH. It will just take longer than if you live in an area of 20% RH.


----------



## Battenkiller

woodgeek said:
			
		

> If there were no binding energy it would dry out completely (eventually).




It will, and without any added energy needed to drive the process.  Any RH/MC chart will show that the EMC of wood at 0% RH is 0%. The problem becomes getting the air down to 0% RH.





> On everything stopping below 32F: The pore water will freeze into ice at 32F, but it will still sublime at the previously liquid/vapor interfaces. The vapor/ice partial pressure at 31F and the vapor/liquid pp at 33F are basically the same, so the drying rate of pore water should not change by much on freezing. Moreover, the adsorbed water isn't ice below 32F, its still adsorbed water.  The water molecules are touching the wood, not each other, and so can't form an ice crystal.  There is no reason why their mobility or vapor pressure should do anything special at 32F either.  I get your water crystals breaking the the structure thing, which is intriguing, but do you have any evidence?  Can't wood fibers be stretchy enough to accommodate the strain?




How will the water bound into the cells sublime once the RH of the air deep inside the wood rises to 100%.  It will happen, but at a greatly reduced rate compared to sublimation occurring at the surface. A moisture gradient will soon be established as water molecules start to leave the ice inside, and the most saturated air will be that closest to the fibers themselves.  Yes, molecules will diffuse into the intercellular spaces and longitudinal tubules, but without a rapid exchange of air like is found at the surface, little sublimation will occur by comparison to the outer surface. 

The damage to the cellular structure in wood is a well documented phenomenon.  There is mention in the literature of this occurring in live trees as well, but in the live tree there are mechanisms that help mitigate this. I had about a face cord of green cherry stored next to my stove over the Thanksgiving holiday.  When it was half gone I brought in replacement wood that had received a deep freeze during the second week of December. The replacement wood was already checked in the ends (hey, if it's not drying out there, the checking must be from freezing damage alone) when I brought it in, but after about 4-5 days it exhibited a very deep checking of the end grain, much deeper than the wood stored in the basement for several weeks more.  You could actually see the diagonal line that separated the old wood from the new in the stack, the new wood looking severely checked in the ends although it most likely still contained a higher moisture content.





> On the end/side drying issue--I think we all know that split wood dries faster, so there must be some drying out the sides.  I saw a study once (can't find it) that said the diffusivity of water is 4x higher along the grain than across it, so a drying front would move in from the ends 2x faster than from the sides (its a square root of D).  Not a huge difference.  The cracking ends are due to the shrinkage being across the grain rather than along it (as lots of folks here will confirm). So, once the wood piece is more than couple times longer than it is wide, that guy will dry as much through the sides as the ends.  That square root business also explains why a 'plank' that is much thinner in one cross grain direction dries so much faster than a square cross section--splitting a square into two planks should dry 4x faster, into 3 equal planks should dry 9x faster etc.




It's nice to know that we have a person on board with a PhD in applied physical chemistry, but I got to thinking, Gee... what if we could consult a guy with a PhD in wood technology.  He might really be able to answer this question.

Then I remembered about a little known book called "Understanding Wood", written by a dude named Bruce Hoadley.  I was in town this morning and decided to finally buy a copy of the book at the local Barnes and Noble.  Here's what Mr. Hoadley has to say about the subject in Chapter 6 "Wood And Water":

... on page 130

"But perhaps the most universal problem is end-checking. Water moves longitudinally through the wood 10 to 15 times faster than it moves perpendicular to the grain. Therefore, end-grain surfaces rapidly lose their moisture and are the first to drop below FSP [fiber saturation point] and begin to shrink. If the shrinkage exceeds 1.5%, tension failures in the form of end-checking may occur.  Here's another way to look at it: let's assume that moisture moves on the average 12 times faster along the grain than across it.  Suppose a board is 1" thick. Up to 6" from either end, water molecules at the mid-thickness of the board have a better chance to escape through the end-grain surface than through the side-grain surface.  Except for the 6" inches near the end, drying from the board should be uniformly slow because most molecules will [have to] escape through the side grain.  The objective of end-coating boards with sealers is to prevent rapid end-drying and create side- grain drying right to the end of the board.  Stresses are ever-present in drying because there must be differential drying in a piece of wood to make moisture move.  If the moisture gradiants are great enough, serious defects will develop."         


So, Mr. Adios might better come to me for the fly tying lessons (I used to be a commercial tier) and seek wood drying advice from Mr. Hoadley when next they meet.





> Sorry to those who hate long posts....




Don't apologize to me, I'm a wordy SOB myself. I really appreciate all you have pointed out.  Others are pointing to the work done on long boards (almost entirely cut 4/4 BTW) even though we are talking about short sections split rather thickly by comparison.  You have obviously taken the time to explain what you know in a way that any of us here can figure out, giving mechanisms that describe the actual movement of water.  You have added to my knowledge base. I hope I have added some to yours.

BK


----------



## JerseyWreckDiver

skyline said:
			
		

> No it only address the question I said it addressed.
> "... which is more important, temperature or Relative Humidity in drying our firewood."
> 
> As stated in previous posts, the data  http://www.woodweb.com/knowledge_base/Wood_Handbook.html Chapt. 12 pg 4 shows in general,  Lower EMC values in "more" places of the U.S. during the summer, thus wood generally dries faster in the summer with no input on our part. This is more pronounced in the arid west than new england.
> But for example Boston's lowest EMC month is February, New York's is April, you throw in local variables of wind and moisture supply and we're back to that old statement for your wood pile, it depends on where you are.
> But the main reason it depends on where you are is because RH is more important in adjusting the EMC conditions than temperature!
> 
> And besides these differences between the EMC across seasons are generally small and we can affect those if we know what to do work on, ie. prioritise RH over temperature.
> 
> My Final Answer, I hope!



Huh? Whats that God? Oh, why yes, he is a mighty fine dancer...


----------



## Battenkiller

And this just in:


http://www.jstor.org/pss/1505844


Seems that sublimation is going on a _lot_ more than I had been giving it credit for.  Bring on the cold.






> *Abstract*
> 
> The winter climatic conditions of much of Canada provide an ideal environment for freeze-drying. We have been attempting to use these conditions for the drying of large waterlogged timbers. In the freeze-drying process, the wood is kept in a frozen state and the drying proceeds by sublimation. We are particularly concerned with the treatment of large timbers which present great difficulties when treated by the accepted methods. A structure was built to keep snow and rain off the wood but which allowed air to pass over it. The structure was covered with polyethylene sheet to allow the sun to shine on the wood surface and heat it. Weight changes in the wood were measured with a load transducer and temperature was followed with thermocouple probes. Temperature and relative humidity of the surrounding air were recorded instrumentally. The timbers were of several varieties of wood in various states of decomposition. All of the wood dried quickly and much of the water was removed. This technique appears to have the potential to treat large quantities of timber in an economic and simple way.




The diagrams shown in the introduction clearly demonstrate the exact effect that was shown in those photos of the frozen oak split that was posted on another thread.  The outside drying by sublimation and the icy part receding toward the center.  I can't get the rest of the article, but I can only guess that there is a diffusion gradient that develops in the wood that allows it to dry as if it was a solid block of ice rather than how an unfrozen piece would dry (much faster at the ends).  In fact, they even tested completely water-logged wood and it dried fine.


So there you go, LLigetfa, you are vindicated at last.  What the eyes see, the heart must believe.


When someone says "scientific study", I usually think of peer reviewed literature, not stuff coming out of the forestry dept.  I know that NY Fishery "biologists" fudge their data, or allow experimental confounds to go uncorrected to allow them to "prove" their point.  _That's_ "junk science". This abstract  comes from a real scientific journal, which to me, gives it orders of magnitude more credibility.


----------



## Rockey

Battenkiller said:
			
		

> And this just in:
> 
> 
> http://www.jstor.org/pss/1505844
> 
> 
> Seems that sublimation is going on a _lot_ more than I had been giving it credit for.  Bring on the cold.
> 
> 
> 
> 
> 
> 
> 
> *Abstract*
> 
> The winter climatic conditions of much of Canada provide an ideal environment for freeze-drying. We have been attempting to use these conditions for the drying of large waterlogged timbers. In the freeze-drying process, the wood is kept in a frozen state and the drying proceeds by sublimation. We are particularly concerned with the treatment of large timbers which present great difficulties when treated by the accepted methods. A structure was built to keep snow and rain off the wood but which allowed air to pass over it. The structure was covered with polyethylene sheet to allow the sun to shine on the wood surface and heat it. Weight changes in the wood were measured with a load transducer and temperature was followed with thermocouple probes. Temperature and relative humidity of the surrounding air were recorded instrumentally. The timbers were of several varieties of wood in various states of decomposition. All of the wood dried quickly and much of the water was removed. This technique appears to have the potential to treat large quantities of timber in an economic and simple way.
> 
> 
> 
> 
> 
> The diagrams shown in the introduction clearly demonstrate the exact effect that was shown in those photos of the frozen oak split that was posted on another thread.  The outside drying by sublimation and the icy part receding toward the center.  I can't get the rest of the article, but I can only guess that there is a diffusion gradient that develops in the wood that allows it to dry as if it was a solid block of ice rather than how an unfrozen piece would dry (much faster at the ends).  In fact, they even tested completely water-logged wood and it dried fine.
> 
> 
> So there you go, LLigetfa, you are vindicated at last.  What the eyes see, the heart must believe.
> 
> 
> When someone says "scientific study", I usually think of peer reviewed literature, not stuff coming out of the forestry dept.  I know that NY Fishery "biologists" fudge their data, or allow experimental confounds to go uncorrected to allow them to "prove" their point.  _That's_ "junk science". This abstract  comes from a real scientific journal, which to me, gives it orders of magnitude more credibility.
Click to expand...


I dont remember anyone here doubting that freeze drying occurs. The argument in this thread is about whether wood will season quicker in the summer or the winter. The facts have proved that summer has a huge advantage over winter in this department in North America. Maybe the magic Canadian air allows for quicker freeze drying -please show that data that proves it is quicker to season in the winter. One puzzling fact is that from the article that you quoted all of the timbers studied were in "various stages of decomposition".


----------



## LLigetfa

Finally a study that addresses the drying of large waterlogged timbers, not thin strips of lumber.

All I know is what I see.  I take wood and stack it tight to the rafters in my shed and over the course of Winter, I see significant shrinkage.  When I stack wood in the shed in Spring, I don't see that same amount of shrinkage over the Summer.  Wood in my shed that is not quite ready for burning heading into Winter, may be suitable for burning at the tail end of Winter.

Mind you, it is an unfair comparison because we have long Winters and short Summers.  Most of what is officially Spring and Fall gets tacked onto Winter in this comparison.  Summer is just two months of lousy skiing.

Some will argue that trying to dry wood in my shed in Summer is not the ideal way, but for an apples to apples comparison, that is where it dries in Winter.  Without a doubt, a kiln would be the best and fastest, but my shed is no kiln.

Shrinkage alone is not a good measure of how much the wood has dried.  When wood dries quickly just at the end grain yet is wet at the core, it forms deep checks which is shrinkage but the shrinkage is internal to the wood and the outer dimension doesn't really change much until the wood has dried to the core.  Once the wood dries all the way through, the deep checks actually close up some unless the wood fibres have deteriorated from repeated wet/dry cycles.  Wood dried in a kiln with the end grain protected has little or no checks.


----------



## LLigetfa

Rockey said:
			
		

> One puzzling fact is that from the article that you quoted all of the timbers studied were in "various stages of decomposition".


Various stages of decomposition is just highbrow talk for dead wood.  Once you cut it from its roots and remove the foliage, it's all dead wood.


----------



## Rockey

It appears that one of the objects of this study was to prove that this is an economical and simple method for drying timbers without the irreversible cellular damage that other methods induce. Sounds like it is very plausible. I would like to see the publication in its entirety.

The statement that " In air-drying the moisture content remains evenly distributed throughout the wood " is quite interesting. This is probably true while the wood is frozen but when it is warm I have seen the exact opposite, i never tried it frozen. I can resplit oak and see a distinctive line that seperates the dry wood from the wet wood.  I can measure the MC from the outer edge to the the distinctive line and the MC incrases proportionally as you approach the line of wet wood. This distinctive line and band of dry wood appears around every edge (all sides and edges).


----------



## Battenkiller

Rockey said:
			
		

> I dont remember anyone here doubting that freeze drying occurs. The argument in this thread is about whether wood will season quicker in the summer or the winter. The facts have proved that summer has a huge advantage over winter in this department in North America. Maybe the magic Canadian air allows for quicker freeze drying -please show that data that proves it is quicker to season in the winter. One puzzling fact is that from the article that you quoted all of the timbers studied were in "various stages of decomposition".



Let's ignore the unfortunate title of this thread that led to 7 pages of debate.  What the OP really asked was this:



			
				thinkxingu said:
			
		

> SO, I posted a few weeks ago asking what to do with oak that was reading around 25-30% moisture and was advised to wait another year.  Well, this morning I went and tested a couple pieces from the same batch and they're reading around 20%.  Can this be right?



Just as nobody doubts that freeze-drying occurs, no one is really saying it happens faster than summer drying... with the possible exception of LLigetfa, for whom it may very well be true.  The OP seemed to be asking if it was possible that the wood he tested had dried 5% in a few weeks of cold weather.  Since he hasn't reported back with his MM findings, I guess we still don't know.  Maybe it did.

I don't think the authors of the paper were trying to prove anything.  Number one, real scientists never set out to prove things. That's not science.  On my interview for my first job as a lab rat, the director (a megalomaniac and an MD, _not_ a scientist) said to me, " I know I'm right, I just haven't been able to prove it yet."  Not an auspicious omen for my scientific aspirations there.  Thankfully, he was just the money man who got the funding.  We then did our own thing with his dough and let him have the limelight.

Secondly, the paper was published in a journal for the conservation of historic and artistic works.  They seemed to be suggesting that the technique could be used for drying large timbers, but that does not appear to be the motivating factor behind the study.  

Everything you are saying about air-drying wood is completely in line with what I know as well, from my own experience and from info I have gathered from the wood industry. That portion of water in wet that leaves along the lateral surfaces does so by establishing a diffusion gradient across the grain.  This is something that is also in the Hoadley book. So I'm not quite sure what they mean by that, and I also wish I could read the entire paper.  Many scientific journals charge big money to institutions to subscribe, and I think this is an antiquated practice in these times of information sharing.  I'm sure this will come to an end in due time, but there are many holdouts in the scientific community.  One of my first lab rat tasks was to read hundreds of PubMed medical journal abstracts looking for papers that pertained to the work we were doing, and then see if the Albany Medical School library had those journals in their stacks so I could get photocopies for our files.  It would have been so much easier to read the entire articles online.  Maybe soon.

I am still waiting to see firewood specific data that confirms that it dries faster from the lateral surfaces than it does from the ends.  4/4 dimensional lumber is very long and has a nominal thickness of only 1", and not too many folks cut, split and stack firewood to that size.  As I quoted from Hoadley above, wood dries _10-15 times as faster_ from the end grain than it does from the sides.  Seems that 16" long splits, therefore, must do much of their drying from the ends, and 12" splits must do most all of their drying that way.  This may be important to the way it can dry by sublimation.


----------



## claudebo

nice conversation! 
this is my first posting so if is miss some sort of protocol plz forgive 
and tell me nicely! 
now some general observations I have made ( this is mainly reference to OP question)
"I posted a few weeks ago asking what to do with oak that was reading around 25-30% moisture and was advised to wait another year.  Well, this morning I went and tested a couple pieces from the same batch and they’re reading around 20% in regards to I posted a few weeks ago asking what to do with oak that was reading around 25-30% moisture and was advised to wait another year.  Well, this morning I went and tested a couple pieces from the same batch and they’re reading around 20%:" 

Moisture meters are not always accurate, you can have green wood that reads 25% and wood that has 
been outside for 1 year also read 25%.  Are they equally dry, no.
I speculate that the meter does not account for the moisture in the wood cells but reads the 
moisture of the longitudinal cells.  The real test is the volume/weight ratio, but that is difficult to do. 
Fortunaly veteran wood burners have the toss and catch method.  Take a piece of wood and toss it a couple inches up and feel the weight of it in your hand.  You would be surprised with a bit of practice how accurate this is.   Of course you need to be thinking of the wood species. Pine will much lighter then
say oak. 

In your case OP it would not be surprising to have a difference of 5% between different pieces of wood.  Think of doing an average of say 20 pieces.  If you really want to get a sense of it cut a couple pieces in the middle, I found this to be a much better reading of the moisture.  

Oak is one of slowest drying wood, but you can burn it at 25% moisture.  If you can bring some indoors for a couple of weeks prior that will also help a lot.  Ballpark:  wood indoors will try about 3 times faster.  
Moisture in wood is always trying to reach and equilibrium with its neighboring wood cells and evtually the ambient environment.  Think of a sponge.  A sponge will always dry from the outside edges toward the middle.  Conversely moisture on the outside of a sponge will travel toward the middle.  IMHO what makes a successful wood pile is time, time and time, more than if it is covered, in a shed, in the sun wind etc.. Although all those factors certainly contribute.  
I cut mine (8 cords) in the fall and use it the following winter so about 12 to 15 months. My moisture readings range from 15% to 22%, the oak being the 22%. 
Oh and finally did your check the batteries in your moisture meter ; )  

For more on wood drying check out: 
http://en.wikipedia.org/wiki/Wood_drying


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## DBoon

Whew, five pages of super-technical explanations from chemists - and I thought engineers were tough in this regard.  Still, I learned a lot.  Thanks to all the chemists for such detailed explanations.  

I have some data here https://www.hearth.com/econtent/index.php/forums/viewthread/44360/ on my hickory and maple seasoning, using not a "moisture meter" (which I assume to be mostly as useful as a car dashboard light that says "overtemperature") but a multimeter using the forest service lookup table for an ohms to moisture content conversion (much more accurate, and consistent).  

I'll continue to update that thread.  Perhaps others will care to also and provide some real data.  I have no pre-determined conclusions, but I do have a hypothesis (it is that wood will dry in the winter, but by how much, I don't know).  If I am proved wrong, I won't be embarrassed, so fear not fudged data.  

I noted the comment from another poster that low temperatures during measurement have to be taken into account as they will provide misleading data.  I won't assume that this is true or false.  But in the future, I will note the temperature my measurement was made at from here on out.


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## LLigetfa

I think some people inferred from my statements that I said wood dries faster in Winter under equally ideal conditions. I don't think I actually said that. What I said is I see the most shrinkage on my stacks over the course of Winter. I also said what I call Winter is much longer than what I call Summer. I believe however that I do get a significant amount of drying over Winter. I think a lot of people think that drying comes to a halt when the wood freezes.

For clarification, I don't own a moisture meter and I have never tried to calculate scientifically how much moisture left when. I have only two points of reference WRT drying. 1, The height of my stacks which indicate shrinkage and 2, the weight of a split gauged only by how it feels in hand.

WRT the height of the stacks, I stated that since wood dries more out the endgrain, deep checks form which indicate shrinkage but the overall height of the stack only happens when the centre also shrinks. This is evidenced by the end checks closing back up. What the percentage of MC is at any particular stage, I haven't a clue. Over the years I've had occasion to stack fresh cut wood both in my shed and in my roundtop. I also moved wood that sat out in a heap all Summer and then got stacked in the shed come Fall. My recollection of what shrank how fast, and when are just that, not scientific record keeping.

When I let wood dry in heaps outside all Summer and then moved it to the shed, I would sort it by relative weight into now, later, and much later stacks. In this case, there is no fair comparison between Summer and Winter drying since a heap out in the rain and laying on top of wet clay is not ideal Summer drying. Neither is stacking tight in a shed with no spacing between rows ideal but at least one face was exposed to the air. That said, as I burned through the "now" wood, the "later" wood got lighter. Depending on how much I had of each, I would take some of the "much later" wood to mix in and was surprised by how much lighter it got over time despite the frozen state.

Last year I decided to change how I lay up wood WRT what time it spent where and when. I built "slotted bins" on the empty half of my woodshed that would keep the stacks stable through the shrinking process so that I could stack fresh split wood in the Spring without concern that the shrinking would topple my stacks. I laid up the stacks so that I had spaces between them that I could in-fill later in the Fall. This gave me the opportunity to observe shrinkage over time as I stacked tight up to the rafters. I was disappointed by how little the stacks shrank versus the other half of my shed that held wood from the prior year. The old side was packed in tight with no spacing between rows and I could see how the exposed face row shrank faster than the ones behind it. In fact, as the exposed end of the stack shrank, it caused the stack to curve and lean from the faster drying through the endgrain.

I have another experiment underway outside. There are three sets of stacks that spent the entire Summer outdoors. One set is two rows on pallets with no space between the rows but covered only on the top. I then have a space and another two rows also on pallets but not covered. In other words, there are two rows, a space, and two more rows. There is another space and a fifth row (exposed on both sides) but not on pallets. Each row is a cord and all this wood will get moved to my shed next Summer after I build my slotted bins on the side that will then be empty. This will be my 2012/2013 wood. A year from now I plan to take delivery of another 12 cord to process for 2013 and beyond.


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## iceman

each side has its given points... but once again it is more on your location to which one is actually gonna be the right one for any person....
yes if you bring wood in the house it will season quickly, my r/h in the house is about  45 right now with a temp of 75... that would equate to a lotta drying... now if i go outside its prolly about 20 degrees with a r/h of prolly 0-10 at about 5 ft off the ground( who knows) with a breeze.... who knows whats happening...
but this is a helluva great debate!


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## Rockey

iceman said:
			
		

> each side has its given points... but once again it is more on your location to which one is actually gonna be the right one for any person....
> yes if you bring wood in the house it will season quickly, my r/h in the house is about  45 right now with a temp of 75... that would equate to a lotta drying... now if i go outside its prolly about 20 degrees with a r/h of prolly 0-10 at about 5 ft off the ground( who knows) with a breeze.... who knows whats happening...
> but this is a helluva great debate!



FYI - the relative humidity in Springfield, Ma as per NOAA is 69%   http://forecast.weather.gov/MapClic...BOX&textField1=42.115&textField2;=-72.539&e=1


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## iceman

Rockey said:
			
		

> iceman said:
> 
> 
> 
> 
> each side has its given points... but once again it is more on your location to which one is actually gonna be the right one for any person....
> yes if you bring wood in the house it will season quickly, my r/h in the house is about  45 right now with a temp of 75... that would equate to a lotta drying... now if i go outside its prolly about 20 degrees with a r/h of prolly 0-10 at about 5 ft off the ground( who knows) with a breeze.... who knows whats happening...
> but this is a helluva great debate!
> 
> 
> 
> 
> FYI - the relative humidity in Springfield, Ma as per NOAA is 69%   http://forecast.weather.gov/MapClic...BOX&textField1=42.115&textField2;=-72.539&e=1[/qu
> 
> 
> 
> lol not on my little temp setup!-- FYI
> Also i am not in springfield tht is the closet city to me right now i am at 42%
> but that could be wrong, it was taken this afternoon, however, even if you look at your link you will see the dewpoint is around 16-18 which is really a key indicator on moisture in the air....
> right now the r/h is 54%...
Click to expand...


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## Rockey

Ok its official... this  thread is now just about as exciting as watching a bucket of water dry (in the wintertime).


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## Battenkiller

Iceman, the RH in your area right now is 78% and the dewpoint is 16ºF.  Temperature is 21º with calm winds. If it drops just 5 more degrees, the RH will be 100%.

In those conditions, if Rockey brings his bucket of ice over to your house, it won't dry...er... I mean _sublimate_ until hell freezes over.


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## savageactor7

Dead wood that's harvested in the winter will dry up pretty fast, 5-10 days depending on conditions.

You would think it would all burn up being dead and all but mostly only the top third is an immediate good burn. The rest I split up and stack in a long row under the lean-to. We withdraw from right to left and continually replace with more recently cut standing dead. Wind helps it dry faster or I can set splits under the hearth for a few hours or up to a day. 

This isn't really seasoning so much as a drying out type operation. But if your desperate for wood this method could be of benefit to you. Another critical task to burn standing dead asap is to make small splits, nothing goes into the stove bigger than my biceps or smaller. After the splits sit by the warm hearth awhile you can feel the difference in heft.







Here's some standing dead harvested yesterday and burning right now.


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## SolarAndWood

savageactor7 said:
			
		

> nothing goes into the stove bigger than my biceps



Given whats in your bucket, you must have some big guns.


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## savageactor7

LOL... No not really that bucket is apple and you know how that is...you can only get so far with it. The bigger splits will languish under the stove for awhile longer. While my objective  is a certain sized split...we can't always get what we want.


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## karri0n

At long last, after seven pages of debate, countless sources referenced for scientific data, and hours of anecdotal evidence, we have FINALLY reached a definitive answer:

Q. Does wood dry faster in summer or winter?

A. Yes.


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## savageactor7

karri0n that was my experience with 'drying' dead wood the OP was talking 'seasoning'. Truthfully I can't remember if the OP was cutting dead wood or live wood and there is a difference...

...just for clarity case someone plans on cutting today.


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## karri0n

savageactor7 said:
			
		

> karri0n that was my experience with 'drying' dead wood the OP was talking 'seasoning'. Truthfully I can't remember if the OP was cutting dead wood or live wood and there is a difference...for clarity.




Oh, I think you need to re-read my question... It's a "trick answer", so to speak.


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## savageactor7

OH ... didn't realized you were the OP. OK then someone cover me I going in for another recon of the OP.


EDIT OK I'm back...guess back in the day I quit reading after the 2nd page...got too complicated. No...not that's is a bad thing, it's me. My fault.

*Water freezing inside the wood expands the cells and allows the moisture to escape more quickly.*
^probably why I can only hand split winter wood with my torn rotator cuff...wouldn't try that in the summer. Ruin my golf game for weeks...


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## iceman

Battenkiller said:
			
		

> Iceman, the RH in your area right now is 78% and the dewpoint is 16ºF.  Temperature is 21º with calm winds. If it drops just 5 more degrees, the RH will be 100%.
> 
> In those conditions, if Rockey brings his bucket of ice over to your house, it won't dry...er... I mean _sublimate_ until hell freezes over.



so you are telling me its does not dry in the winter??
all this time i have been waiting for hell to freeze over??


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## iceman

Rockey said:
			
		

> Ok its official... this  thread is now just about as exciting as watching a bucket of water dry (in the wintertime).



how bout you bring the bucket.. i got the water...  we can put beer in it while we are waiting..... (and you bring the lady from your previous post)
and we will have fun in the wintertime.. !


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## Battenkiller

iceman said:
			
		

> Battenkiller said:
> 
> 
> 
> 
> Iceman, the RH in your area right now is 78% and the dewpoint is 16ºF.  Temperature is 21º with calm winds. If it drops just 5 more degrees, the RH will be 100%.
> 
> In those conditions, if Rockey brings his bucket of ice over to your house, it won't dry...er... I mean _sublimate_ until hell freezes over.
> 
> 
> 
> 
> so you are telling me its does not dry in the winter??
> all this time i have been waiting for hell to freeze over??
Click to expand...


No, I'm telling you that no matter how low the dewpoint goes, it won't dry much at 78% RH.  I'll bet the RH dropped considerably during the hottest part of the day today, though. However, I didn't check it so I don't know.

Hey, can I join you guys for the beer?


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## Rockey

iceman said:
			
		

> Rockey said:
> 
> 
> 
> 
> Ok its official... this  thread is now just about as exciting as watching a bucket of water dry (in the wintertime).
> 
> 
> 
> 
> how bout you bring the bucket.. i got the water...  we can put beer in it while we are waiting..... (and you bring the lady from your previous post)
> and we will have fun in the wintertime.. !
Click to expand...


I got the first round of Sam Adams.


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## iceman

Rockey said:
			
		

> iceman said:
> 
> 
> 
> 
> 
> 
> 
> Rockey said:
> 
> 
> 
> 
> Ok its official... this  thread is now just about as exciting as watching a bucket of water dry (in the wintertime).
> 
> 
> 
> 
> how bout you bring the bucket.. i got the water...  we can put beer in it while we are waiting..... (and you bring the lady from your previous post)
> and we will have fun in the wintertime.. !
> 
> Click to expand...
> 
> 
> I got the first round of Sam Adams.
Click to expand...


listen i love sams.. if you are coming with the bucket... i will have a couple of kegs and food ... i have driven to toledo a couple of times ... so i will handle it ...just dont forget the "company"  lol


hey batten!!  hell ya you can come  i am not youg so can't kill a keg anymore... but the 3 of us prolly could!!


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