What is too low for moisture readings?

[Ashful]

So in a nut shell - yes - wood can be TOO dry (hence the MFG warning of KD stuff) and YES - too dry of wood can cause a dirty burn and the possibility of an overfire. Cord wood stacked in the elements - probably not an issue.

I suspect the overwhelming majority of all "my wood is too dry," statements come from inaccurate moisture meter measurements, either defective meters or operator error. That said, with sufficient time under shelter, the equilibrium moisture content of firewood stacked in Bridgeport CT will eventually settle in at 13%.

 

[Jutt77]

Here is the deal: Too low of MC can cause the outgassing of the wood to exceed the stoves ability to burn them. This results in a dirty burn. If the dirty gasses don't get burned, they go up the stack. This can also cause an overfire situation for your stove if sufficient control isn't there (remember - the control of the stove is designed around ~20% MC).

So in a nut shell - yes - wood can be TOO dry (hence the MFG warning of KD stuff) and YES - too dry of wood can cause a dirty burn and the possibility of an overfire. Cord wood stacked in the elements - probably not an issue.

Thanks for the explanation, I've read something published a while back that mentioned the same things I just couldn't remember exactly what. Same paper suggested mixing too dry with some wetter wood as Lumber-Jack suggested.

To further beat this poor dead horse, what percentage is considered too dry? I just split up some standing dead (10yrs) Rocky Mtn Juniper on Saturday that is at 12%. I'll probably just mix it but curious if I can burn it alone.

 

[Jags]

To further beat this poor dead horse, what percentage is considered too dry?

I am not real sure that there is a specific number. My stove might be able to handle 13% just fine and maybe somebody's cat can handle 10%. Draft will make a difference also.
If I were burning 12% stuff and I am not sure how the stove will react, I would do like I tell every new burner. Start small - see where it goes. Or in your case...mix a little in that has a higher MC. I don't think 12% is gonna melt your stove, but that is just my opinion.

ETA: Keep an eye on your pipe. Smoke or no smoke...that is the question (and answer).

 

[tsquini]

The moisture can never be too low. It just burns differently. The drier the wood is, the hotter the fire will burn. You just have to be aware of the stove top temperature and that it is not over firing the stove when using drier wood.

 

[HDRock]

I appreciated HDRock's comment about people burning kiln dried wood -- I'm planning on doing just that come December. My Builder is saving my 2x6 and 2x4 cut offs for me. Says there's a nice pile going! He also stacked my logs from the trees that got cut down to build the house. Still, I hope my kiln dried is dry enough since it is piling up outside (not that it ever rains in Oregon ) .

I would get it off the ground and cover it up and keep it dry
Just remember the scraps can burn hot n fast ,so, don't load stove full right off the bat, do small loads or mix in with cord wood ,until you get an idea of what you can control.

 

[jillybeansisme]

Thanks again, HDRock; however, I won't be there until mid-December and it is piling up as we speak. I plan to get it stacked when I am there (and cover it up).

 

[Lumber-Jack]

Simple solution: buy a catalytic stove.

Actually I would like to get a catalytic stove, but it's a ways down on my priority list.
I did however just buy a new chainsaw, which got bumped to the top of the list when my 30+ year old Husqvarna muffler bolt broke for the umpteenth time. Oh well, she was a good saw and served me well for more than 30 years.

 

[bobdog2o02]

Simple solution: buy a catalytic stove.

My BK will burn dirty on super dry wood, the first time i burned a local brand of eco brick. They manufacture their product from the waste of large local custom cabinet manufacturers. It got a bit out of hand, the cat was VERY active when i dialed it back and this created more "off gassing" than the cat could gobble up. It continued for 3 hrs till the load cooled down. With uber dry wood this can happen.

 

[BCC_Burner]

Simple solution: buy a HYBRID stove.

FIFY...

 

[bobdog2o02]

FYIY? what's that mean?

I also fail to see how that would help unless the stove is engineered to run at 1000° and use 8% moisture wood.

 

[Ashful]

My BK will burn dirty on super dry wood, the first time i burned a local brand of eco brick. They manufacture their product from the waste of large local custom cabinet manufacturers. It got a bit out of hand, the cat was VERY active when i dialed it back and this created more "off gassing" than the cat could gobble up. It continued for 3 hrs till the load cooled down. With uber dry wood this can happen.

I suspect this depends almost entirely on cat combuster size vs. load or firebox size, as you're right in pointing out that super dry wood can gas out quick enough to overcome most cat's. However the cat stove does give you the ability to more tightly control the burn rate, and thus the out-gassing rate, if you don't let it build up too much head of steam before dialing back. It actually reminds me of several comments I've seen posted about running a non-cat on normal wood, in terms of having to dial it back before it gets going too good, lest it run away on you.

I also fail to see how that would help unless the stove is engineered to run at 1000° and use 8% moisture wood.

I could run my stove < 500F stuffed full of KD framing lumber. The cat combuster might rocket up to 2200F, but the stove top and body can be whatever temperature I want. I would assume your BK has even better control.

 

[Lumber-Jack]

To further beat this poor dead horse, what percentage is considered too dry? I just split up some standing dead (10yrs) Rocky Mtn Juniper on Saturday that is at 12%. I'll probably just mix it but curious if I can burn it alone.

View attachment 139222

If I'm getting any reading at all on the moisture meter I figure it's probably pretty good (providing it's below 20%). The wood I consider low MC is the stuff that won't register at all on my moisture meter.

OK, so people are going to say to themselves, how is no reading at all on the meter possible? Surely the wood must contain some moisture?
The answer is, moisture meters are calibrated for specific woods and moisture content, the more crucial of these, I believe, is what moisture content they are calibrated for, and most of the inexpensive ones we use for firewood are calibrated to be most accurate around 15% - 25% MC. Anything much above or below that will give increasingly inaccurate readings. In fact most of these moisture meters simple peg out or read OL, (Over Limit) on anything above 30% because the reading are just not accurate above that.. By the same token many pin type meters, including mine, will just peg out to 0% on anything much below 10%. So the dry wood I'm talking about could be anything from 0% to 10% or more, likely it is closer to 10% than 0% though because the ambient humidity just doesn't get down to 0% so it's pretty unlikely the wood could be that dry.
So although my meter isn't perfectly accurate, it's more accurate then guessing, and it will confirm accurately enough when my wood is too wet to burn properly, when it's within acceptable limits to burn, and when it's a little on the dry side. And that's about all I really need to know.

Not to get too far off topic, but while on the topic of moisture meters one other thing my moisture meter has helped me with has to do with selecting the trees I cut for firewood. I mainly cut beetle kill lodgepole pine. These trees are one of the few trees that can be cut down and burned immediately with no need to spit and season before burning, providing I'm careful to select the trees that have been standing (and seasoning) long enough. When these lodgepole pine die from the beetles their needles turn orange then gray as the moisture continues to leave the tree. By using my moisture meter I have found that the trees with the orange needles require at around 6 months to dry after cutting and splitting, but the trees with gray needles are dry enough to burn immediately. That alone is useful enough information for me because it means I can do all my cutting for the winter heating in the fall just before I need it, which is when I prefer to cut my wood.
Also another useful bit of information I have found with my moisture meter is that these same lodgepole pine trees that may have fallen to the ground on their own will actually reabsorb moisture very quickly once they are laying on their side, even if they are being held up off the ground by their branches or other fallen trees. Knowing this I now know that if I want wood to burn my wood immediately then I will need to avoid cutting these trees that already laying down, even though they seem like easy pickings, because they won't be ready to burn unless they are split and seasoned for a year.

 

[Jutt77]

Not to get too far off topic, but while on the topic of moisture meters one other thing my moisture meter has helped me with has to do with selecting the trees I cut for firewood. I mainly cut beetle kill lodgepole pine. These trees are one of the few trees that can be cut down and burned immediately with no need to spit and season before burning, providing I'm careful to select the trees that have been standing (and seasoning) long enough. When these lodgepole pine die from the beetles their needles turn orange then gray as the moisture continues to leave the tree. By using my moisture meter I have found that the trees with the orange needles require at around 6 months to dry after cutting and splitting, but the trees with gray needles are dry enough to burn immediately. That alone is useful enough information for me because it means I can do all my cutting for the winter heating in the fall just before I need it, which is when I prefer to cut my wood.
Also another useful bit of information I have found with my moisture meter is that these same lodgepole pine trees that may have fallen to the ground on their own will actually reabsorb moisture very quickly once they are laying on their side, even if they are being held up off the ground by their branches or other fallen trees. Knowing this I now know that if I want wood to burn my wood immediately then I will need to avoid cutting these trees that already laying down, even though they seem like easy pickings, because they won't be ready to burn unless they are split and seasoned for a year.

Good tips on finding seasoned standing beetlekill lodgepole as we have a lot of that around here as well.

Delmhorst MMs are calibrated for Douglas Fir and provides a species correction chart to your first point. This is really useful for Lodgepole (listed as SPF) as the correction is quite substantial. There's also a temperature correction chart but that isn't really statistically significant unless you're outside of a 50-90f range:

 

[Seanm]

Both very good posts Jutt77 and Lumber-Jack. So when Im reading 20% on my Lodgepole I'm really seeing 25%.... I will have to absorb that for awhile. I wonder if its the same for four pin? I guess for me most of my collecting is done in the spring and my mm readings are anywhere from 15% to 25% so I should be good. I might have to pull and split a few from the stacks and check them out as I'm curious. I find it interesting my Larch on that chart is pretty close to dead on with the numbers I see on the mm. Off to walk the dog and look for a few standing dead Lodgepole! Jutt77 I would be curious to see that temperature chart if you don't mind?

 

[Lumber-Jack]

Yes. I have actually seen that chart before and knew that lodgepole reading need to have a few extra % points tacked on to them to help calibrate. There was a former active member here "Battenkill" who described how he took readings on some of his wood with his hand held meter and calculated exact MC of this same wood by weighing and microwave drying it and then re-weighing it again, and then compared those findings to his hand held meter reading and found very little difference. I wanted to try his technique on some lodgepole pine just to see how correct these calibrations corrections were but didn't want to spend the money on letter scale just to try the experiment.

 

[Jutt77]

Both very good posts Jutt77 and Lumber-Jack. So when Im reading 20% on my Lodgepole I'm really seeing 25%.... I will have to absorb that for awhile. I wonder if its the same for four pin? I guess for me most of my collecting is done in the spring and my mm readings are anywhere from 15% to 25% so I should be good. I might have to pull and split a few from the stacks and check them out as I'm curious. I find it interesting my Larch on that chart is pretty close to dead on with the numbers I see on the mm. Off to walk the dog and look for a few standing dead Lodgepole! Jutt77 I would be curious to see that temperature chart if you don't mind?

The chart above came with my Delmorst meter and may or may not apply to other brands of meters. Meter readings would be dependent on species a meter is calibrated against and there may be some other factors so proceed with that in mind.

Here's the temp chart:

Entire manual is here: http://www.delmhorst.com/Documents/PDFs/Operating-Instructions/J-Lite.pdf

 

[Jutt77]

Yes. I have actually seen that chart before and knew that lodgepole reading need to have a few extra % points tacked on to them to help calibrate. There was a former active member here "Battenkill" who described how he took readings on some of his wood with his hand held meter and calculated exact MC of this same wood by weighing and microwave drying it and then re-weighing it again, and then compared those findings to his hand held meter reading and found very little difference. I wanted to try his technique on some lodgepole pine just to see how correct these calibrations corrections were but didn't want to spend the money on letter scale just to try the experiment.

Now that's interesting, I have a pretty accurate postage scale...

 

[Seanm]

The chart above came with my Delmorst meter and may or may not apply to other brands of meters. Meter readings would be dependent on species a meter is calibrated against and there may be some other factors so proceed with that in mind.

Here's the temp chart:

Entire manual is here: http://www.delmhorst.com/Documents/PDFs/Operating-Instructions/J-Lite.pdf
View attachment 139363
View attachment 139364

Neat thanks. As I was out walking the dog I was thinking that I should contact the company that I purchased my meter from and see if they have a chart to go off of. May be similar may not be.

 

[HDRock]

If I'm getting any reading at all on the moisture meter I figure it's probably pretty good (providing it's below 20%). The wood I consider low MC is the stuff that won't register at all on my moisture meter.

OK, so people are going to say to themselves, how is no reading at all on the meter possible? Surely the wood must contain some moisture?
The answer is, moisture meters are calibrated for specific woods and moisture content, the more crucial of these, I believe, is what moisture content they are calibrated for, and most of the inexpensive ones we use for firewood are calibrated to be most accurate around 15% - 25% MC. Anything much above or below that will give increasingly inaccurate readings. In fact most of these moisture meters simple peg out or read OL, (Over Limit) on anything above 30% because the reading are just not accurate above that.. By the same token many pin type meters, including mine, will just peg out to 0% on anything much below 10%. So the dry wood I'm talking about could be anything from 0% to 10% or more, likely it is closer to 10% than 0% though because the ambient humidity just doesn't get down to 0% so it's pretty unlikely the wood could be that dry.
So although my meter isn't perfectly accurate, it's more accurate then guessing, and it will confirm accurately enough when my wood is too wet to burn properly, when it's within acceptable limits to burn, and when it's a little on the dry side. And that's about all I really need to know.

Not to get too far off topic, but while on the topic of moisture meters one other thing my moisture meter has helped me with has to do with selecting the trees I cut for firewood. I mainly cut beetle kill lodgepole pine. These trees are one of the few trees that can be cut down and burned immediately with no need to spit and season before burning, providing I'm careful to select the trees that have been standing (and seasoning) long enough. When these lodgepole pine die from the beetles their needles turn orange then gray as the moisture continues to leave the tree. By using my moisture meter I have found that the trees with the orange needles require at around 6 months to dry after cutting and splitting, but the trees with gray needles are dry enough to burn immediately. That alone is useful enough information for me because it means I can do all my cutting for the winter heating in the fall just before I need it, which is when I prefer to cut my wood.
Also another useful bit of information I have found with my moisture meter is that these same lodgepole pine trees that may have fallen to the ground on their own will actually reabsorb moisture very quickly once they are laying on their side, even if they are being held up off the ground by their branches or other fallen trees. Knowing this I now know that if I want wood to burn my wood immediately then I will need to avoid cutting these trees that already laying down, even though they seem like easy pickings, because they won't be ready to burn unless they are split and seasoned for a year.

I agree with pretty much all of that and most of the same thing applies for the dead standing ash or on the ground ash around here, if it's dead standing it's probably ready, on the ground the bark will suck up and hold moisture

 

[HDRock]

I have some 45 year old (originally kiln dried) oak boards, stored inside mostly unheated, uncooled , what's your guess at the equilibrium moisture content in my area ?

 

[Squirrel]

USDA Moisture equilibrium info.
Find out here. http://www.woodweb.com/knowledge_base/fpl_pdfs/fplrn268.pdf
I guess it still depends if you're in a swamp or on a hill top though!

 

[Lumber-Jack]

I agree with pretty much all of that and most of the same thing applies for the dead standing ash or on the ground ash around here, if it's dead standing it's probably ready, on the ground the bark will suck up and hold moisture

Yep, I've confirmed it time and time again. In fact just last week my family and I went out cutting wood, we dropped a number of trees, bucked them up and loaded the rounds into the truck. When it became obvious we didn't have enough to fill the truck I started preparing to fall another tree, but wife pointed out that there was already a rather large tree laying down close to the area I dropped the other trees, and she suggested I just buck that one up. I told her to get the moisture meter I always keep in the chainsaw tool box and I went over and bucked a section out of that fallen tree and said if the moisture meter reads less than 20% I'll buck it up. It didn't, it pegged the meter at well over 30%. If I was cutting in the spring I would have no problem taking that tree, but I'll be needing this wood this winter and there is plenty more standing dry trees around.

 

[Ashful]

I have some 45 year old (originally kiln dried) oak boards, stored inside mostly unheated, uncooled , what's your guess at the equilibrium moisture content in my area ?

Yes. I don't know what MC% they dried lumber to in 1970, but these days framing lumber is dried to 8 - 10%, and will actually expand / go up in MC% in the weeks after coming out of the kiln. Mass hardwood is likely "over-dried" a bit, too... but I suspect more of the specialty hardwood dealers stop near equilibrium MC%. Kilning hardwood is an expensive proposition, both in terms of energy usage and shelf time.

Either way, it doesn't matter if that 45 year old oak was KD'd or AD'd. It's at equilibrium after 45 years under cover.

 

[bobdog2o02]

Yes. I don't know what MC% they dried lumber to in 1970, but these days framing lumber is dried to 8 - 10%, and will actually expand / go up in MC% in the weeks after coming out of the kiln. Mass hardwood is likely "over-dried" a bit, too... but I suspect more of the specialty hardwood dealers stop near equilibrium MC%. Kilning hardwood is an expensive proposition, both in terms of energy usage and shelf time.

Either way, it doesn't matter if that 45 year old oak was KD'd or AD'd. It's at equilibrium after 45 years under cover.

I think you missed his question,

what's your guess at the equilibrium moisture content in my area ?

but i think the tables in squirrel's post pretty much answered the question

 

[Lumber-Jack]

It's at equilibrium after 45 years under cover.

What! I thought 3 years was a long time, now you say I have to season my firewood for 45 YEARS? !