My Seasoning Season Ended….2 month ago…Drying Experiment Cont'

[woodchip]

From the graphs what should be clear is that the fresh "live" c/s/s wood will dry quickly at first, practically no matter the conditions. See Portland's weather last April-June if you have any doubts.

Thanks for this follow up post, I'm following this with a lot of interest.

Taking this thought of fast initial seasoning no matter what the conditions, I'm going to put my thoughts here if I may.

The rapid loss of the first part of moisture occurs because the wood is damper than most dry or humid days, and will also give up more moisture while the sapways (is that the right term) are more open after cutting.

If this is the case, cutting in the early fall will allow seasoning to take pace during the fall/winter while the split is still relatively wet, and will continue to season well the following Summer when the humidity should be lower and seasoning conditions better.

On that basis, with good wind flow and a dryish Summer, most wood would dry well with in one year of cutting where you are.

Now for the acid test. Have you any plans to burn your test wood against some which has been seasoning for, say, 3 years ???

 

[skyline]

Thanks to all for the interest.

What is the average windspeed at your house skyline? Do you show up on the map as at least fair?

(broken link removed to http://www.nrel.gov/gis/pdfs/windsmodel4pub1-1-9base200904enh.pdf)


Someone here is eventually going to develop a model that predicts with a high level of certainty how long it takes to dry any piece of firewood anywhere. .

You have to remember that wind map is for the resource 50m high and I haven't been able to get my stacks quite to that level. In all seriousness, I don't think wind is a major factor in drying here, its all about EMC and from a practical perspective it is more about the size/shape of your split. See my 2nd post in this thread. The 2 splits were from the same tree c/s/s the same day and only differed by 3.5 lbs.(16.3 vs. 12.8) After 4 months during the summer the small one is at 11%, the bigger one at 22% and you know that last 5% takes longer that the first 50% to lose. I'll have to wait until next spring before the big piece gets to 16% if I leave it outside in our climate.

THIS IS outstanding work, real science!

i have read through the posts quickly.....but..what caused the increase of moisture around day 175 or so?

Barkeater,

I'm not sure it's at the level of real science, just persistence with a scale.
Day 175 was Oct. 12. If Oct.'s weather picture doesn't give you an idea why the wood gained weight, just let me know :roll: What is more remarkable is how much water the wood lost in April and May (see those weather pics). After 42 days of drying, 30 of them with rain, my average split went from 100% MC to 52%! July's picture also explains why the Maple which I c/s June 21 dried so much faster than the fir.

would I want good ventilation to the outside?

Conventional wisdom says ventilation or breeze.

I also figure if there is no ventilation you will have a high level of humidity from the green wood.

True, that why you need to provide ventilation, whether it is mechanical or natural (wind). The air surrounding the splits would otherwise quickly approach 100% RH, at which point drying essentially ceases. However, you don't need as much air movement as you might think. Just a few MPH of moving air has a remarkable effect on drying time. That's a lot easier to do outside than inside a shed, which is why most folks dry outside in single rows and move the wood into the shed once it is dry.

I agree with BK, but I'll bite and buck conventional wisdom. As BK said you need air flow but not that much. There is no question an open sided shed or stack will dry the wood in a year+ so if that works for you go for it. But based on my results, BK's, and others, I am going to build a closed up wood shed that is insulated. A small 4.7" computer fan will move 60 cfm or 3600 cu. ft. of air per hour. That means I could exchange the air in a 8' tall shed 12'W X 37' long every hour. Boost the fan size for any inefficiencies, add some solar heat, which lowers the RH, and exhaust the humidity in a shed that stays above outside temps every night and all winter long and I think I'll speed up my drying time over an open sided shed, especially in our weather.

From the graphs what should be clear is that the fresh "live" c/s/s wood will dry quickly at first, practically no matter the conditions. See Portland's weather last April-June if you have any doubts.

Thanks for this follow up post, I'm following this with a lot of interest.

Taking this thought of fast initial seasoning no matter what the conditions, I'm going to put my thoughts here if I may.

The rapid loss of the first part of moisture occurs because the wood is damper than most dry or humid days, and will also give up more moisture while the sapways (is that the right term) are more open after cutting.

If this is the case, cutting in the early fall will allow seasoning to take pace during the fall/winter while the split is still relatively wet, and will continue to season well the following Summer when the humidity should be lower and seasoning conditions better.

On that basis, with good wind flow and a dryish Summer, most wood would dry well with in one year of cutting where you are.

Now for the acid test. Have you any plans to burn your test wood against some which has been seasoning for, say, 3 years ???

Woodchip, You have nailed. If you can, don't waist your good drying months when the wood is really wet, use them on the last few %MC you need to lose. Again it's the difference in wood MC and EMC that controls the drying rate. As my graphs and BK has noted, the closer your wood MC is to EMC, the slower it will dry. So raising the temp. and lowering the RH around your wood will always speed up drying.

 

[barkeatr]

THIS IS outstanding work, real science!

i have read through the posts quickly.....but..what caused the increase of moisture around day 175 or so?

Barkeater,

I'm not sure it's at the level of real science, just persistence with a scale.
Day 175 was Oct. 12. If Oct.'s weather picture doesn't give you an idea why the wood gained weight, just let me know :roll: What is more remarkable is how much water the wood lost in April and May (see those weather pics). After 42 days of drying, 30 of them with rain, my average split went from 100% MC to 52%! July's picture also explains why the Maple which I c/s June 21 dried so much faster than the fir.

hA!, I TRUE scientis, your even scientific and humble in response!

I understand what your saying now. the weather where i live is always like October, so I dont notice a difference. My mind, in order to survive, sort of numbs rainy weather out. I work in it like any other day.
my last question that has probably been answered already, was this wood under cover? I assume not. In my climate, i dont leave any wood out to dry in the open, it just rots. it has to go under cover to dry.

anyway thanks again.

barkeater

 

[barkeatr]

opps i did not do teh qoute thing correct in my post above.

 

[GatorDL55]

THIS IS outstanding work, real science!

i have read through the posts quickly.....but..what caused the increase of moisture around day 175 or so?

tim barkeater

Wood is hygroscopic, meaning that it readily absorbs moisture around it. (sort of like a sponge) Even if the humidity is up, and you have your stacks covered, the weight will increase just from pulling moisture from the air. This will continue until equilibrium is reached (i.e. wood will lose moisture if the air is dry and will gain moisture if the air has more than the wood.)

 

[skyline]

THIS IS outstanding work, real science!

i have read through the posts quickly.....but..what caused the increase of moisture around day 175 or so?

tim barkeater

Wood is hygroscopic, meaning that it readily absorbs moisture around it. (sort of like a sponge) Even if the humidity is up, and you have your stacks covered, the weight will increase just from pulling moisture from the air. This will continue until equilibrium is reached (i.e. wood will lose moisture if the air is dry and will gain moisture if the air has more than the wood.)

That is true but most of the extra weight is probably surface water in the bark and outside edge and will dry relatively quickly compared to the first time it lost it.
This document shows the EMC state month by month in your neck of the woods and gives you an idea that there isn't a huge difference throughout the year.
(broken link removed)

As I recall, these figures are based on outside temperatures, but in the shade and under cover. If your wood's MC reaches your outdoor EMC, then its good enough to burn almost everywhere. The trouble is when your wood is at 23% and EMC is at 18, there isn't much gradient between the two to cause the moisture to leave the wood and it takes a long time for it to dry that last 5%. (Like a "year of seasoning"!)
But if you had a solar shed that increased the temp, lowered the RH and EMC down to 10, even for just a few hours, the gradient between the two would cause the moisture to leave much more quickly and it won't reabsorb as fast or much above the average EMC state.

 

[maplewood]

Me cut wood.
Me split wood.
Me stack wood.
Me wait one year.
Me put wood in basement.
Me burn wood.
Me warm.
Me done.

 

[Jags]

Me cut wood.
Me split wood.
Me stack wood.
Me wait one year.
Me put wood in basement.
Me burn wood.
Me warm.
Me done.

No where in there did I see "Me drink beer". COMPLETELY UNACCEPTABLE.

 

[skyline]

Me cut wood.
Me split wood.
Me stack wood.
Me wait one year.
Me put wood in basement.
Me burn wood.
Me warm.
Me done.

No where in there did I see "Me drink beer". COMPLETELY UNACCEPTABLE.

Hate to add more controversy or "fuel to the fire" but Jags is right, sometimes wood has a higher purpose than burning or all this weighing stuff :exclaim:

 

[firefighterjake]

Me cut wood.
Me split wood.
Me stack wood.
Me wait one year.
Me put wood in basement.
Me burn wood.
Me warm.
Me done.

Pretty close . . . for me add in . . .

Me put wood in shed.
Me wait a second year.

Well that . . . and I'm never done . . . I'm always working on my wood.

 

[Battenkiller]

That is true but most of the extra weight is probably surface water in the bark and outside edge and will dry relatively quickly compared to the first time it lost it.
This document shows the EMC state month by month in your neck of the woods and gives you an idea that there isn't a huge difference throughout the year.
(broken link removed)

As I recall, these figures are based on outside temperatures, but in the shade and under cover. If your wood's MC reaches your outdoor EMC, then its good enough to burn almost everywhere. The trouble is when your wood is at 23% and EMC is at 18, there isn't much gradient between the two to cause the moisture to leave the wood and it takes a long time for it to dry that last 5%. (Like a "year of seasoning"!)
But if you had a solar shed that increased the temp, lowered the RH and EMC down to 10, even for just a few hours, the gradient between the two would cause the moisture to leave much more quickly and it won't reabsorb as fast or much above the average EMC state.

There's that link! I've been trying to find that so I don't have to keep taking screen captures of my PDF version.

Yeah, that table just about says it all, and you don't need to be a rocket scientist to understand it. Look up the closest city to your area, that's how dry your wood can get outside under cover. Nobody's gonna cheat this, no matter how long the wood sits. And your very intelligent explanation of the small moisture gradient at the end influencing the drying time gives insight into why there is so much disparity in perceived drying times across the membership.


Take these two examples (I already did the Photoshop work on this last night):


Dennis out in Michigan vs. CT.

Dennis' EMC is 3-4 points higher than these cities in CT. As his wood approaches 20% MC, it is only 3 points above his EMC, while in CT, their wood would be 6-7 points above EMC, meaning a much stronger gradient is driving the drying time, so it will get there a lot quicker. Also, Dennis seasons his wood outside as do most folks. That's probably the fastest way for wood to shed its free water load, but as it approaches EMC, every drop of water will set it back some. It will perpetually be getting set back to the same low-gradient conditions that made it finish off so slowly in the beginning. That's why I think it's best to dry outside for several months to a year, then get it under cover so it can finish to EMC without additional water being added.

Of course, as you mentioned, this gradient will be mostly on the outside, but I believe that that is the most important part to get dry. The biggest problem with marginal wood is slow ignition. Once the fire is well established it should burn OK, but if you can't get the outside going good, it's just gonna sit there and smolder on you. For fast starting fires, I'll take 25% MC on the inside and 15% on the outside any day over straight 20% through and through.

 

[Battenkiller]

I agree with BK, but I'll bite and buck conventional wisdom. As BK said you need air flow but not that much. There is no question an open sided shed or stack will dry the wood in a year+ so if that works for you go for it. But based on my results, BK's, and others, I am going to build a closed up wood shed that is insulated. A small 4.7" computer fan will move 60 cfm or 3600 cu. ft. of air per hour. That means I could exchange the air in a 8' tall shed 12'W X 37' long every hour. Boost the fan size for any inefficiencies, add some solar heat, which lowers the RH, and exhaust the humidity in a shed that stays above outside temps every night and all winter long and I think I'll speed up my drying time over an open sided shed, especially in our weather.

I don't believe it's quite so simple. What I meant by my comment above is that it doesn't take much airflow to get the air between the splits below 100% RH, but kiln-drying studies have shown that wood dries much faster if you can increase the air velocity across the wood surfaces to the point where is changes from laminar flow to turbulent flow. It's not just about air exchange inside the container, it's about actually increasing the chances that any given water molecule will lift off the surface and go into the surrounding air. I'd have to look it up to get the correct velocities, but if you download a copy of "The Dry Kiln Operator's Manual" it's all in there. My feeling is that you will be happier with bigger fans directed right at the ends of the splits and through the stack.

 

[Jags]

but kiln-drying studies have shown that wood dries much faster if you can increase the air velocity across the wood surfaces to the point where is changes from laminar flow to turbulent flow.

And this explains the reason that wood in my chicken coop (plenty of ventilation) does NOT season as fast as wood in single row stacks outside - even with the few degrees of thermal gain that the coop provides, the wind that the outside stacks get - trumps it.

 

[Battenkiller]

but kiln-drying studies have shown that wood dries much faster if you can increase the air velocity across the wood surfaces to the point where is changes from laminar flow to turbulent flow.

And this explains the reason that wood in my chicken coop (plenty of ventilation) does NOT season as fast as wood in single row stacks outside - even with the few degrees of thermal gain that the coop provides, the wind that the outside stacks get - trumps it.

Jags, you're a tech geek like me. Download that kiln operator's manual. It's heavy going but manageable. Chapter Two alone is worth the price (free) of admission. It's interesting to find out that even in controlled situations like a kiln, there are enough variables within wood that they have to constanly check to see that the wood has actually dried down to where it's supposed to be. That's a big point Sky is driving home. It just might take a year or two for all the variables to even themselves out. Those poor dry kiln operators don't have the luxury of infinite time like we do.

 

[Jags]

....there are enough variables within wood.... That's a big point Sky is driving home.

Oh, I took a look at the download. It is interesting - I would like to think that every wood worker out there would like to have that at their finger tips.

For us woodBURNERS I think your statement above hits home. It is something that has been said time and time again on this forum (It Depends), but now we can actually base it on factual info. No more guestimating WHY. And it also backs up the often repeated mantra of "split, stack, season for two years and you should be good to go". Could it happen sooner - sure. But that covers the bases as about complete as one can while only using a single statement.

 

[skyline]

I agree with BK, but I'll bite and buck conventional wisdom. As BK said you need air flow but not that much. There is no question an open sided shed or stack will dry the wood in a year+ so if that works for you go for it. But based on my results, BK's, and others, I am going to build a closed up wood shed that is insulated. A small 4.7" computer fan will move 60 cfm or 3600 cu. ft. of air per hour. That means I could exchange the air in a 8' tall shed 12'W X 37' long every hour. Boost the fan size for any inefficiencies, add some solar heat, which lowers the RH, and exhaust the humidity in a shed that stays above outside temps every night and all winter long and I think I'll speed up my drying time over an open sided shed, especially in our weather.

I don't believe it's quite so simple. What I meant by my comment above is that it doesn't take much airflow to get the air between the splits below 100% RH, but kiln-drying studies have shown that wood dries much faster if you can increase the air velocity across the wood surfaces to the point where is changes from laminar flow to turbulent flow. It's not just about air exchange inside the container, it's about actually increasing the chances that any given water molecule will lift off the surface and go into the surrounding air. I'd have to look it up to get the correct velocities, but if you download a copy of "The Dry Kiln Operator's Manual" it's all in there. My feeling is that you will be happier with bigger fans directed right at the ends of the splits and through the stack.

BK, I think we mostly agree. And yes I will have a fan to mix the air in my wood shed. My point was to show that a tiny computer fan could remove all of the air in a typical shed several times every hour which brings the humidity inside back down to ambient. I think most folks who have experience with wood drying slowly in a shed is because there is virtually no air flow or mixing going on at all.

I think the kiln example is not quite applicable as I don't think there will be laminar flow going on around my splits or anyone else's.

My understanding is the following: laminar flow conditions develop in kilns because they are blowing through evenly spaced flat lumber, not splits. Also, they are intentionally keeping the RH high to prevent drying too quickly but just below the wood and moisture from the wood can lead to saturated conditions in laminar flow. For the wood to dry evenly, the air must be mixed well (turbulently) so that RH is constant throughout the kiln and lumber doesn't check from uneven drying. Since my RH will be as low as I can make it, just a small amount of air flow and venting should remove all the moisture the wood can give up. And I won't care if my splits dry unevenly as long as the wet ones have time to catch up to the dry ones. So I think your statement that it doesn't take much airflow to dry splits is right on.

Another factor driving all this is that not only does our EMC average over 16 for 5 moths this time of year but a lot of stacks outside around here turn to fungus after more than a year.

 

[skyline]

I found this typical Kiln drying schedule and thought it might be helpful. Basically it looks like they keep the EMC within 20% of the wood MC to prevent damage but far enough to drive the moisture out in a hurry.

It's only after the first 4 steps do they drop the RH below 70% and raise the temp above 110. No wonder folks can dry their wood quickly in the SW when EMC may hit 2 or 3 everyday.

Also, you don't need to have temperatures at 100 degrees or above to have a low EMC. Just 70 °F and 20% RH will give you an EMC of 4.5.

 

[jonwright]

Ooooo....good info. My thoughts were indeed correct: Stack wood where it will get sun and wind.

Fits with the observation that mud puddles dry in the sun and wind faster than in shade and no wind - why wouldn't my wood stack?

Although I will say I'm pleasantly surprised by how fast the wood can dry.