Interesting moisture testing results--range of woods

[dreezon]

So... I went out to the wood piles, took some pieces and started splitting and taking moisture readings (Harbor Freight meter). I must say, it was an education. It may change the order and manner in which I burn my wood. Bear in mind, I bought my stove last fall and started harvesting wood in summer of 09. I have to burn what I have, but at least I can guarantee it will be drier than what I burned last year (still saved $800 on my heating bills).

So here's what I found:

Red Oak (split and stacked July 09): MC mostly in upper teens. A few isolated spots as high as 22 or 23% (Some of these were very fat splits too)
Sugar maple (split and stacked November 09): MC Mostly mid to upper teens, one or two spots as high as 21 or 22%
Hackberry and Soft Maple (purchased and stacked March 2010): MC Consistently in mid teens (This stuff was not seasoned and was wet with snow when I got it.)
Black Locust (split and stacked Aug-Sept 09): MC from upper teens up to mid 20s ! (Considering its low initial MC, I was surprised. Split pieces stayed within 22, but rounds much higher.
Osage (split and stacked Aug-Sept 09): MC from upper teens up to 22%
Honey Locust (split and stacked Sept 09): MC ranging from mid teens to mid 20s (this stuff had been bucked since May! Some pieces were good and dry; others not nearly dry enough)
I also had a bit of cherry and mulberry, but I haven't tested any of these yet.

I was pleasantly surprised by the levels on the oak and maple. Very pleased with the hackberry and soft maple considering it was actually in the shade of my house.

One question: How do you figure the MC of a given piece of wood? Do you go by the worst (wettest) spot on the split or do you average that with the 75% that is in the mid to upper teens? If you go by the average, I would say almost every piece was at or below 20%, but if you go by the worst part, I've got a lot of marginal pieces.

I tried to take my moisture readings from parts of the split that are furthest from an outer edge. Seems they are always most moist near bark.

Further information:
I stored most of this wood in an open, fairly sunny area with a good amount of wind exposure. I also keep a tarp over the tops of my racks during non summer months and hang some plastic during the winter to prevent rain and snow infiltration.

 

[Wood Duck]

I think it is the average moisture content that you should go by. Seems like all of this wood is about ready to burn.

 

[CJRages]

Interesting information. Thanks for sharing. Did you have a hot and dry summer there in Peoria? It looks like that wood is in great shape for burning this winter. Great news that the red oak is good and dry already.

Missouri had an above average hot summer - rainfall was normal. Lots of sizzling hot days with good wind speeds. October here has been one of the driest on record (so far .15" of rain) with above avg. temperatures to boot. My most seasoned stuff was cut & split in Jan, but I don't have a moisture meter to give any additional info.

 

[Battenkiller]

I think it is the average moisture content that you should go by. Seems like all of this wood is about ready to burn.

+1

Looks like you're doing it righter than a lot of folks. You'll be warm this winter for sure.

 

[wendell]

Adding a second stove this fall, I robbed some of my wood for next year so was checking different types to see what I could use this year and what need to wait until next and found similar results to you. Some of the same type in the same row would be quite different. I think that is the real benefit of getting 2 and 3 years ahead, letting those outlier pieces enough time to be ready too.

 

[Backwoods Savage]

Hey dreezon, I haven't seen many posts from you lately. Hope all is well with you.


Can we assume that you resplit the wood before checking the moisture? Does it perhaps make you wonder with all the various woods being so close to the same that maybe the meter is not entirely accurate? However, you will probably be well satisfied with the results you get this coming winter. Hope you stay nice and warm.

 

[wendell]

Also, I use the highest reading I get on a split as the moisture content for that piece.

 

[dreezon]

Hey dreezon, I haven't seen many posts from you lately. Hope all is well with you.


Can we assume that you resplit the wood before checking the moisture? Does it perhaps make you wonder with all the various woods being so close to the same that maybe the meter is not entirely accurate? However, you will probably be well satisfied with the results you get this coming winter. Hope you stay nice and warm.

Hey, Backwoods. I'm well. Thanks for asking. I appreciated all your help and advice last year.

I did, in fact, resplit each piece, and I tried to split them down the center so as to get a "core" reading.

True, the meter is not the most reliable, but I was seeing enough in the way of "trends" to make me believe that I was getting meaningful results. Also, with any given piece I would see variances that made sense... a few percent drier toward the point of the split where it's thinner and near the ends. Of course, it also makes a difference how far you press the points into the wood, so I tried to press them in as far as I could.

 

[Swamp Fox]

So, today I began cutting rounds from one of the dump truck loads of logs that were delivered last week. The trees were cut down recently. In light of what I had been reading regarding the length of time it takes for red oak to season, I decided to check the moisture content of some red oak and white oak splits. The red oak splits were extremely heavy and gave the appearance of being damp to wet. I have a Delmhorst J-2000 moisture meter, which I checked for calibration and set the setting for outside temperature. Anyway, the white oak splits read at around 35% to 36% MC. All the red oak splits read at 99.9% moisture content. No wonder it takes three or more years for the red oak to season! I'm separating the red oak splits from the white oak splits, so I'll start burning the white oak during the 2013-2014 season, and the red oak after all the white oak is burned.

 

[Gark]

Should we question the accuracy of moisture meters that don't ask what species of wood they're measuring?
The moisture meter I got does not ask what species its probes are into. But a resistance table-to-moisture-content listing
got from this site shows, for instance - for 20% moisture content - American Elm is .48 Megohms and Paper Birch is 2.50 megohms. That's a big spread. Other species are somewhere in between. Any cheapo moisture meter that doesn't ask what species it is, does nothing more than an ohmmeter measuring resistance in megohms. It is simply reading out resistance on a different scale than megohms.. It claims "moisture content". But it doesn't take into account the species. After getting misled by the WILD GUESS readings on the cheapo MM from HF, I more trust the age-old methods of measuring moisture content: How heavy is it .. how long has it been C/S/S .. does a newly split surface feel 'cold' .. does it sound like a bowling pin or like a chunk of playdough when dropped on the concrete floor? Does it sizzle when burning? Is there serious checking on the ends? The cheapo meters without species-specific programming cannot give an accurate percentage of moisture reading.
Oh hey your stacking and storing method sounds righteous and it all sounds great to burn. What I'm saying is .. the meter only confirms what has already been done to rightly season the wood.

 

[Backwoods Savage]

Gark, although I've never owned nor used a moisture meter, your comments I find interesting as I've never heard of this before. How have you came to your conclusions about the types of woods, etc.?

 

[Lumber-Jack]

All you have to do is read the specs on those moisture meters and they will tell you they have a certain degree of inaccuracy, usually around 2-3% depending on the wood being tested and what end of the meters range the wood being tested is at. Most are calibrated to be most accurate between 10% and 20% MC which is fine for our purposes. For most wood burning needs the small degree of inaccuracy within that usable range is really not important. For instance, we are generally looking to get our firewood under 20% , if our meter has say a 3% degree of inaccuracy then to be safe we should try and get a reading of say around 17% on our meter to be sure it below that 20% mark. Of course that inaccuracy could go the other way and our wood is actually closer to 14% at that 17% reading on the meter. Still, at least we know our wood is dry enough to burn. Now, if we start banging, dropping, feeling and listening to our wood, I really wonder if you are going to be any more accurate than 3%. I mean, different types of wood feel and sound different. Oak is much heavier and denser than pine, heartwood is denser that sap wood, do you really think that pieces of pine that are 15% MC will sound the same (when banged together) as pieces of oak at the same moisture level? Certainly someone with a lot of experience with a particular type of wood will be able to tell when a piece of oak, or pine is well seasoned and ready to burn, but what about when they run into a type of wood they have no experience with? And what about those who have no experience at all? Surely a moisture meter would render more meaningful and accurate readings than a greenhorn could by banging to pieces of wood together. Unless of course your moisture meter is perhaps broken, as possibly Gark's could be. ;-)

 

[golfandwoodnut]

I agree with Carbon Liberator, we are not measuring moisture content for wood working, where it might be that critical. We just want to know if it is realatively safe to burn the wood. 20 percent or less is the number to look for. The only thing I find frustrating is that the last 2 or 3 percent can seem to take forever. I often get that 22 or 23 percent reading. I am sure it will still burn fine, I never get a sizzle or have a problem. I have plenty under 20.

 

[iceman]

All you have to do is read the specs on those moisture meters and they will tell you they have a certain degree of inaccuracy, usually around 2-3% depending on the wood being tested and what end of the meters range the wood being tested is at. Most are calibrated to be most accurate between 10% and 20% MC which is fine for our purposes. For most wood burning needs the small degree of inaccuracy within that usable range is really not important. For instance, we are generally looking to get our firewood under 20% , if our meter has say a 3% degree of inaccuracy then to be safe we should try and get a reading of say around 17% on our meter to be sure it below that 20% mark. Of course that inaccuracy could go the other way and our wood is actually closer to 14% at that 17% reading on the meter. Still, at least we know our wood is dry enough to burn. Now, if we start banging, dropping, feeling and listening to our wood, I really wonder if you are going to be any more accurate than 3%. I mean, different types of wood feel and sound different. Oak is much heavier and denser than pine, heartwood is denser that sap wood, do you really think that pieces of pine that are 15% MC will sound the same (when banged together) as pieces of oak at the same moisture level? Certainly someone with a lot of experience with a particular type of wood will be able to tell when a piece of oak, or pine is well seasoned and ready to burn, but what about when they run into a type of wood they have no experience with? And what about those who have no experience at all? Surely a moisture meter would render more meaningful and accurate readings than a greenhorn could by banging to pieces of wood together. Unless of course your moisture meter is perhaps broken, as possibly Gark's could be. ;-)

Great, some of my wood was 23% it could really be 26% .. bummer

 

[fjord]

Luddites rejoice: no Moisture Meter.

If you have the time, a graduate course in statistics will give you Levels of Significance for the ranges of accuracy of this wildly inaccurate tool with a penetration of 1 mm.
Do you have the kind of time to deal with megohms and re-splitting splits ? Whew. We need firewood.

Here's the Luddite manner of determining seasoning:

1. Eye Method--is the wood a grey color with checked ends ? Usually Dry.

2. Weight Method: are the splits heavy (relative) and maybe feel damp ? Not dry.

3. Baseball Bat Method: knock two splits together. If a dull thud, then not dry. If a slight ringing (like hitting a ball with an ash bat), it is ready to burn.
Corollary to above Bat Method: as above explained, drop on concrete floor.

and, finally #4. The Burn Test: If the split placed onto a bed of red coals sizzles hard with bubbles bursting out the ends, it is not dry and not seasoned.

This Forest Gump stuff.

 

[golfandwoodnut]

Luddites rejoice: no Moisture Meter.

If you have the time, a graduate course in statistics will give you Levels of Significance for the ranges of accuracy of this wildly inaccurate tool with a penetration of 1 mm.
Do you have the kind of time to deal with megohms and re-splitting splits ? Whew. We need firewood.

Here's the Luddite manner of determining seasoning:

1. Eye Method--is the wood a grey color with checked ends ? Usually Dry.

2. Weight Method: are the splits heavy (relative) and maybe feel damp ? Not dry.

3. Baseball Bat Method: knock two splits together. If a dull thud, then not dry. If a slight ringing (like hitting a ball with an ash bat), it is ready to burn.
Corollary to above Bat Method: as above explained, drop on concrete floor.

and, finally #4. The Burn Test: If the split placed onto a bed of red coals sizzles hard with bubbles bursting out the ends, it is not dry and not seasoned.

This Forest Gump stuff.

I hear ya, but unfortuneatly these unscientific methods are not conclusive. I have plenty of grey wood with checked ends that are not under 20%. I have wood that is extremely light (Oak) when compared to wet Oak, but still not ready. Boy if you can rely on the sound that is amazing since different species sound different. I can get any wood to burn on a hot bed of coals, most of which never sizzle. None of these methods indicate if the wood is ideal. Don't you really want ideal wood, if possible? Let the marginal stuff get ready. Now if you waited 2-3 years on everything, no need to do any of the tests.

 

[dreezon]

Luddites rejoice: no Moisture Meter.

If you have the time, a graduate course in statistics will give you Levels of Significance for the ranges of accuracy of this wildly inaccurate tool with a penetration of 1 mm.
Do you have the kind of time to deal with megohms and re-splitting splits ? Whew. We need firewood.

Here's the Luddite manner of determining seasoning:

1. Eye Method--is the wood a grey color with checked ends ? Usually Dry.

2. Weight Method: are the splits heavy (relative) and maybe feel damp ? Not dry.

3. Baseball Bat Method: knock two splits together. If a dull thud, then not dry. If a slight ringing (like hitting a ball with an ash bat), it is ready to burn.
Corollary to above Bat Method: as above explained, drop on concrete floor.

and, finally #4. The Burn Test: If the split placed onto a bed of red coals sizzles hard with bubbles bursting out the ends, it is not dry and not seasoned.

This Forest Gump stuff.

I hear ya, but unfortuneatly these unscientific methods are not conclusive. I have plenty of grey wood with checked ends that are not under 20%. I have wood that is extremely light (Oak) when compared to wet Oak, but still not ready. Boy if you can rely on the sound that is amazing since different species sound different. I can get any wood to burn on a hot bed of coals, most of which never sizzle. None of these methods indicate if the wood is ideal. Don't you really want ideal wood, if possible? Let the marginal stuff get ready. Now if you waited 2-3 years on everything, no need to do any of the tests.

I agree. I've seen wood go gray and checked well before it was ready. And I've had green fresh-split wood that rings like a bell when smacked together (honey locust). Weight can also be pretty difficult, inexact and subjective to judge. It certainly can't tell you the difference between 20% and 25%, especially on red oak, which has so much moisture to lose. I would love to just have all my wood seasoned for 2 to 3 years and not worry about it at all, but I just don't have the space to accommodate that much wood.

I think the moisture meter helps, especially if you take a lot of readings from a lot of samples. That is helpful to know, however, that different woods have different inherent levels of resistance. I would like more information on that subject so I can factor that into the readings I'm getting.

Regardless, I will stay away from woods like red oak and seek the dryer species (black locust, cherry, maple, hackberry, etc.) as much as possible.

 

[Lumber-Jack]

That gray look is almost meaningless to me. All the wood in the picture below is < 20% MC. The only gray wood is in the bottom left corner of the wood shed. And the only reason that stuff is gray is because of the water dripping off the roof got that portion of the wood wet and it's been sitting there long enough that it allowed that gray (black) bacteria to grow on it. Other than that my wood goes from a kind of white (as you see in the wood stacked in the foreground) to a yellow color (as seen in the wood shed). If I allowed the wood to sit out in the open, exposed to the weather, for a few years it would all get gray, but it wouldn't mean that it's any more "seasoned", because it's already seasoned. In fact it would absorb more moisture being exposed like that, so the gray color for me means that it has gotten wetter, not drier.

 

[Battenkiller]

That is helpful to know, however, that different woods have different inherent levels of resistance. I would like more information on that subject so I can factor that into the readings I'm getting.

Below is a species correction table that will help you with most common firewoods. It was compiled by Delmhorst, the foremost maker of moisture meters for the wood industry.


Still, there are better methods that are 100% accurate all of the time and need no species correction at all:


http://www.richardjonesfurniture.com/Articles/microwave-dry-wood/microwave-dry-wood.html


And you thought I was the first... :roll:

 

[Battenkiller]

And the only reason that stuff is gray is because of the water dripping off the roof got that portion of the wood wet and it's been sitting there long enough that it allowed that gray (black) bacteria to grow on it... so the gray color for me means that it has gotten wetter, not drier.

Bingo.

Here is a photo of some bitternut hickory and red oak. It was delivered last December and stored outside for about two months, under a tarp to keep the snow off it. During sunny days there would be lots of moisture evaporating and re-condensing back onto the wood when it cooled off. This allowed microbial action to take place and for the ends to start graying in spots. Then I brought it inside to dry by the fire, where it proceeded to check like a bastard. I posted this pic last week and it drew a comment about not needing to overseason my wood like that.

Truth is, the wood was only inside for about a week when this photo was taken. After two weeks I took one of these pieces (#9 on the table below) and a couple more from outside (7&8) and did my infamous microwave moisture content test on it. It was still at 31% MC at the time of the test. The hickory from outside was at 41%, so the hickory in the photo was probably still at over 35% when the photo was taken. An oak split (#10) taken from wood in the same photo came in at 53% MC! Not hardly ready for prime time.

 

[fjord]

Excellent points...BUTT, who has that kind of time ? We heat 100% with self harvested wood from our woodlands.
While I may have other O.C.D.'s, spreadsheeting the moisture content of the firewood splits with an admittedly inaccurate
tool ( think: the pins enter the wood how far for the megaohms ? ) is too much. Enough to harvest, stack, burn. Got enough on our plate.
In winter the firewood is harvested, bucked in place, then trailered and stored in butts until the split and stacking over spring into summer.
Most goes into the woodshed ( ~ 5-6 cords ). The rest is open stacked for fall burns.
Been done that way since we bought and built in '99. The wood does fine with hardly a sizzle or creosoted flues.

Eyeballing, end checks, weight, color work fine for most.
P.S. I hated statistics.

 

[Battenkiller]

While I may have other O.C.D.'s, spreadsheeting the moisture content of the firewood splits with an admittedly inaccurate
tool ( think: the pins enter the wood how far for the megaohms ? ) is too much.

P.S. I hated statistics.

Fjord, apparently you didn't really read my entire post:

...and did my infamous microwave moisture content test on it.

That data was gathered from a solitary MC test made using the oven-dry method... specifically, a microwave oven.


https://www.hearth.com/talk/threads/53683/


This moisture content assessment method is not subject to any of the inaccuracies inherent with meters. The wood is weighed, all the water is driven from the wood and then it is re-weighed. The difference between the two weights represents the water lost during drying. According to the American Society for Testing and Materials (ASTM), Standard D-4442, the correct formula to use is: total water removed divided by the oven-dry weight times 100 = %MC. No pins, no megaohms, no species correction needed. And 100% accurate for the entire piece, not just the very center of a split.

Yes, you are correct about the need for concern regarding the depth of the meter pins. The wood could be 10% on the outside and 60% on the inside after a week or two of hot, dry, windy weather. But just about everybody here knows by now that you have to split the wood again and read from a fresh internal face, so this concern is unfounded when the reading is taken correctly. The only worry with doing it this way is that some folks get paranoid as all get out when they get a reading higher than 25%MC on the inside when the average MC of the entire split may well be a lot lower than that. Let them stick it back outside for another year if they're worried, it won't really hurt anything as long as it doesn't get too dry - unlikely with wood exposed to the elements.

For the record, I have zero interest in doing this on a regular basis. I only did it that one time to demonstrate the method to others and to get a reasonable assessment of the effect of indoor wood storage in my stove room on moisture content in my firewood. I put the results into a spreadsheet merely to present the data. I didn't feel the need to run it through the statistical package in Excel. Myself, I just love statistics, but I really don't anticipate getting together a large enough sample size using this method to get useful results. Now, if a dozen or so folks feel like getting involved in providing large amounts of drying data using this method of moisture content assessment, I'd be only too glad to run the stats on it. In the meantime, don't hold your breath.

As I have said before, if you have a kitchen scale and don't want to buy a meter, doing this once or twice a year wouldn't take any longer than sharpening a chain by hand, and is a heck of a lot easier to learn. Hardly an imposition, particularly for burners who haven't been at it since 1999. FWIW, there are a lot of folks here been burning a lot longer than since 1999. Some, like Dennis (Backwoods Savage) have been at it for half a century. I'm just a baby at it by comparison, only been at it since the 70s but have been heating this place and the place before this one for nearly 25 years, 24/7, 6-7 months/yr... exclusively with wood. Burned over 150 full cord in that time. Learned a bit along the way, and I'm still here to tell the story.

 

[fjord]

While I may have other O.C.D.'s, spreadsheeting the moisture content of the firewood splits with an admittedly inaccurate
tool ( think: the pins enter the wood how far for the megaohms ? ) is too much.

P.S. I hated statistics.

Fjord, apparently you didn't really read my entire post:

...and did my infamous microwave moisture content test on it.

That data was gathered from a solitary MC test made using the oven-dry method... specifically, a microwave oven.


https://www.hearth.com/talk/threads/53683/


This moisture content assessment method is not subject to any of the inaccuracies inherent with meters. The wood is weighed, all the water is driven from the wood and then it is re-weighed. The difference between the two weights represents the water lost during drying. According to the American Society for Testing and Materials (ASTM), Standard D-4442, the correct formula to use is: total water removed divided by the oven-dry weight times 100 = %MC. No pins, no megaohms, no species correction needed. And 100% accurate for the entire piece, not just the very center of a split.

Yes, you are correct about the need for concern regarding the depth of the meter pins. The wood could be 10% on the outside and 60% on the inside after a week or two of hot, dry, windy weather. But just about everybody here knows by now that you have to split the wood again and read from a fresh internal face, so this concern is unfounded when the reading is taken correctly. The only worry with doing it this way is that some folks get paranoid as all get out when they get a reading higher than 25%MC on the inside when the average MC of the entire split may well be a lot lower than that. Let them stick it back outside for another year if they're worried, it won't really hurt anything as long as it doesn't get too dry - unlikely with wood exposed to the elements.

For the record, I have zero interest in doing this on a regular basis. I only did it that one time to demonstrate the method to others and to get a reasonable assessment of the effect of indoor wood storage in my stove room on moisture content in my firewood. I put the results into a spreadsheet merely to present the data. I didn't feel the need to run it through the statistical package in Excel. Myself, I just love statistics, but I really don't anticipate getting together a large enough sample size using this method to get useful results. Now, if a dozen or so folks feel like getting involved in providing large amounts of drying data using this method of moisture content assessment, I'd be only too glad to run the stats on it. In the meantime, don't hold your breath.

As I have said before, if you have a kitchen scale and don't want to buy a meter, doing this once or twice a year wouldn't take any longer than sharpening a chain by hand, and is a heck of a lot easier to learn. Hardly an imposition, particularly for burners who haven't been at it since 1999. FWIW, there are a lot of folks here been burning a lot longer than since 1999. Some, like Dennis (Backwoods Savage) have been at it for half a century. I'm just a baby at it by comparison, only been at it since the 70s but have been heating this place and the place before this one for nearly 25 years, 24/7, 6-7 months/yr... exclusively with wood. Burned over 150 full cord in that time. Learned a bit along the way, and I'm still here to tell the story.

Whew...what an effort in science! Again: we use firewood for heating, don't have the time to do testing,,,,microwave or not. Nice job however.

BTW: hand sharpening is the ONLY way to do a chain. It's fast, safe, accurate, cheap. Not much skill.

Forgot: been using wood stoves, running workshops on wood and forestry and chainsaws ( for fun and education while having another career ) since the wood stove "renaissance" way back in the 1970's...also. Welcome to the club of real world experience.

Does anyone here ( besides Msr. WebMaster, know who Jay Sheldon is/was ? ) PM me for a full C.V. which you may (or not)receive.

 

[dreezon]

[quote

Still, there are better methods that are 100% accurate all of the time and need no species correction at all:


http://www.richardjonesfurniture.com/Articles/microwave-dry-wood/microwave-dry-wood.html


And you thought I was the first... :roll:[/quote]

This chart is nice, but it doesn't include some key woods for me: honey locust, black locust & osage orange for instance. Any ideas where I can find stats on those woods?

What's interesting is that the Oak and Maple numbers actually match the uncorrected number. They must intentionally calibrate the meters to work for these very common North American woods. Or maybe I'm not understanding things correctly.

 

[Battenkiller]

What's interesting is that the Oak and Maple numbers actually match the uncorrected number. They must intentionally calibrate the meters to work for these very common North American woods.

Actually, if you look carefully at the table, red oak and Douglas fir are the only species that are true to the meter readings at all moisture contents. All major makers of moisture meters calibrate them using the standard timber in the wood industry - Douglas fir (the same wood as is used during the EPA burn tests). All of the other species have to be figured out one at a time using the oven-dry method and comparing the results with meters calibrated for Douglas fir. It is only coincidence that oak has dielectric properties similar to Doug fir, and therefore, gives completely accurate results with resistance meters.

Yet another thing red oak has going for it. Too bad you have to wait about a thousand years before you can actually use the meter on it. ;-P