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Deconstructing Denniswood

Post in 'The Wood Shed' started by Battenkiller, Oct 20, 2011.

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  1. Danno77

    Danno77 Minister of Fire

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    Exactly what I wan to know. And are we talking about a wood having 30% initial, dry down to 15% and then being able to fluctuate up to 18% max, or up to 23% max?

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  2. WoodPyro

    WoodPyro New Member

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    Short term MC aside, I personally feel if you leave a bunch of stacks uncovered depending on where they are and where you live in relation to rainfall, some part will eventually get punky and or slightly rotten, especially around thick bark. Also, especially if other trees' leaves and debris fall on the stacks and contribute to decay. Ideally, I think wood should be split from rounds within 3 months and then after the first year be covered as in a woodshed or nice cover. Obviously never leave bottom layer on ground unless you are sacrificing it.
  3. fire_man

    fire_man Minister of Fire

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    When I told the Postmaster I was sending firewood cross country, he thought I was nuts. Then I told him it was "Denniswood" being shipped for analysis and he understood and suggested I insure the package! :lol:

    Batten: Thanks for the great posts. It was well worth it to finally get some analysis performed on that cryptonic firewood!
  4. fire_man

    fire_man Minister of Fire

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    Sorry I missed all these great posts for so long. You know how being an Engineer is these days, takes a lot out of you at work, that's why I love the firewood hobby!
  5. Battenkiller

    Battenkiller Minister of Fire

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    Glad the thread is still open for you, man. It was your initiative (and your $10) that got the wood here in the first place. :)
  6. Battenkiller

    Battenkiller Minister of Fire

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    Yes.

    No, species is irrelevant to anything but the actual resistance meter readings. Within a given set of conditions, all species will eventually come to the same basic EMC over time. Some species may take a lot longer to get there is all.

    Oh, no, I never said that. Wood can go from 0% MC straight from the oven right up to about 28% MC, just sitting there in air that is 100% RH. The Savash that Tony sent me is still sitting on the tray on my balance beam. It went from an oven-dry 251.3 grams at 0% MC up to 266.6 grams at 6% MC, just sitting in the kitchen air. I suspect it will get up to about 10% MC in several more days... the same MC as just about all my interior woodwork is right now because it is all sitting in air that's at same RH.

    Oh, it might get even wetter than green if you submerge it. Fresh cut white ash is almost devoid of free water, so it has a MC down in the 30% range. But soak some seasoned ash underwater for several months and it will get so waterlogged that you'd think it was oak.

    You have my permission, but your wood will be happier if you keep a hat on it after it is seasoned. I found a 3-4% difference this season between wood was under cover all season long and wood that got rained on all season long. 3-4% doesn't mean anything to me, but among those cranks who are out there every day sticking holes in their wood while waiting for their wood stacks to pass lower than that magical 20% threshold, it will certainly make for some unhappy campers. Especially because they passed that mark way back when the meter said 25%, but they refuse to accept the rules regarding what a resistance meter is actually telling them. :coolgrin:
  7. Battenkiller

    Battenkiller Minister of Fire

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    OK, I've been waiting for someone to comment on the meter reading in the upper right hand corner. 28% MC after seasoning for at least two full years (who knows... maybe longer).

    I've seen poster after poster talk about problems with his or her stove, saying his wood was at 22% MC after being re-split and measured on an inside face. Almost universally, they are told that the problem is likely the wood, that EPA stoves need really dry wood, that the meter must be inaccurate, that you absolutely have to get below 20% MC as measured on the inside of the split in order to get decent burns with an EPA stove. Mix in some kiln-dried wood, or pallet wood, or just give up and try again next year when the wood is ready.

    Or alternatively just cut, split, and stack it a a sunny and windy location for two years and it will be good to go. Obviously, the above photo demonstrates that it may still show above 20% MC when a reading from the inside is taken with an accurate meter. I think this study has shown that my meter is accurate to at least a couple percentage points (probably even more accurate if I had taken the time to take enough well-placed readings to get the correct moisture gradient inside the split).

    And yet, this same wood from the same source was placed in an EPA stove at the Woodstock plant and just wowed everybody with it's incendiary results. And as the owner and processor of this wood has told us time and again, he heats his entire home with only about 3 cord of the stuff. Not just room-temp warm, either, we're talkin' warm enough to get the lady folk to start stripping.

    How can this be?

    [​IMG]
  8. oldspark

    oldspark Guest

    There is still some people on this forum that think wood has to be in the low teens to burn well, not buying it at all. I checked the moisture on some 2x4 I split for kindling this morning and it was 14 to 15 %, thats pine that who knows how old it is so that as low as I will ever see here I think.
  9. Flatbedford

    Flatbedford Minister of Fire

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    So do we conclude that the need for 20% MC and years of seasoning are a myth? Or, is there more to seasoning wood than simply lowering the MC? Does the seasoning do something else top change the wood? Has the cellular structure been altered? Density changed? I know that well seasoned wood just feels different than green wood. Scientifically speaking what besides MC changes as wood seasons? Remember that most species also get harder to split and cut after being seasoned too.
  10. firefighterjake

    firefighterjake Minister of Fire

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    At last . . . I was waiting for someone to offer the Cliff Notes version of this whole test . . . thanks Flatbed.
  11. Jags

    Jags Moderate Moderator Staff Member

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    There will be a test on Wednesday.
  12. Flatbedford

    Flatbedford Minister of Fire

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    But, like with Cliff's Notes, you probably won't pass the test with my post. Check #80. I didn't have quite right.
  13. Battenkiller

    Battenkiller Minister of Fire

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    Conclusions:

    Like most of the threads I start, this one is a stealth thread. By that I mean that it's not at all about seasoning wood, or how well a split of "X" MC will burn in an EPA stove. It's entirely about using a moisture meter correctly for your needs as a woodburner.

    When we were standing outside the Woodstock building and I tested the freshly-split white ash at 28% MC, it was all I could do to hide a smirk. "Surely, this is telling only a portion of the real tale", I thought. "If only I had this split in hand back home, I could do an oven-dry test for MC and find what it really is." Tony graciously sent it my way, so I was only too happy to do the test.

    Nearly every poster I have seen post results of their meter reading seems to have the wrong idea about what this reading means. Those I have spoken to seem to want to ignore the fact that their meter is calibrated to give a reading using a dry-basis calculation. At the Woodstock gathering I was explaining the huge difference between the two methods and a member implied that I must be using some sort of voodoo math, maybe like David Stockman used to invent Reaganomics. Sorry, but it's the same math we used in grade school, just applied in a manner most people think is wrong. Too bad the people designing and using these meters in an industrial setting think otherwise, because for their purposes, they work perfectly fine just as they are.

    For some reason, burners here don't want to believe that the meter is giving them a different result than they are looking for. They believe that the meter is giving them the percentage of water by weight that is present in the original wood, but in fact, it is giving them the percentage of water by weight compared to the weight of dry wood fiber in the sample. The difference can be huge. In short, if you don't understand the relationship between wet-basis and dry-basis calculations, you might as well throw the thing away.

    The only thing that matters to a wood burner is the wet-basis calculation. It is consistent throughout it's range and is linear in relation to water content variations in the samples. Simply put, what you want to know is how much water is in a split weighing "X" pounds. The meter will not give you this information directly... you have to use a simple arithmetic formula to get what you want. I wish it wasn't so, but it is very true.


    The formula was stated in bold text in the original post. I'll try to say it differently.


    Take the reading on your meter and add 100 to it. Then divide the meter reading by the new (higher) number. For example, let's look at a split of red oak (Red oak needs no species correction) that reads 25% on the meter:


    25+100=125 25/125=20% MC wet-basis, or 20% water by weight. 5% lower. Big difference, eh?


    Let's try another one, a split of douglas fir (also needs no species correction) that reads 33% on the meter:

    33+100=133 33/133=25% MC wet-basis, or 25% water by weight. 8% lower. Bigger difference.


    How about a 50% reading (I'll ignore the fact that meter aren't that accurate at that MC)

    50+100=150. 50/150=33% MC. 17 points difference! That's enormous, and it gets progressively more disparate as the MC climbs.


    If the meters actually worked beyond that point and used the same calculation method, a piece of wood that is 50% water by weight would read 100% MC on the meter, and one that is 2/3 water by weight would read 200% MC on the meter! Mind-numbing... but true. If you don't convert this you will have no idea how much water your wood really contains, simple as that.


    How would you feel if you were driving a car that displayed your average speed on the speedometer instead of the speed you're actually traveling at? Or one that gets progressively further from the real speed the faster you go. In meter speak, that would be like seeing you are moving along at 20 mph when you are only doing 16, or seeing 25 when you are doing 20, 33 when you are doing 25, 50 mph when you are crawling along at 33 mph, or 100 mph when you are really cruising at 50.


    Burners using meters also want to blithely disregard the importance of species correction needed in using any meter... and the more significant problem of actually having enough experience to be able to identify the species in question. This makes meter use very problematic for new burners who aren't sure if they have either hickory or tulip poplar... a difference of 5 1/2 points of correction between the two.


    When I did the oven-dry MC assessment on Dennis' wood, I quoted it in dry-basis terms (like a moisture meter would read), and then converted it over to wet-basis terms (like a stove designer would speak of). In simplest terms, I drove out every last bit of water - 54.2 grams - from 306.6 grams of well-seasoned ash. That is to say, the wood was 17.7% water by weight, even though the meter said it was 28% inside. And 17.7% MC is almost exactly between the the lower and upper range of MC used when your stove was originally tested for those emissions and heat output numbers it is supposed to have. The EPA test calls for using wood that is between 16% and 20% MC wet-basis. Is it any shock that it burned so well in the Woodstock stove? Why wouldn't it? At just under 18% MC, it's simply perfect.

    Bottom line? Wood needs to be seasoned, it's just a question of how dry and how long it takes to get there. A general guideline is that it needs a minimum of a year stacked outside, two is better and three might be better yet in some geographical areas. But if you grab a split of hickory from a two year-old stack and crack it open only to find out it's still reading 28% MC on your meter, don't be alarmed. It's really telling you that your wood is at 20% MC in the very middle, and that the average MC for the entire split is even lower.

    BTW Dennis.... have you fallen asleep yet? :)
  14. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Not yet BK. Still awake here.
  15. Battenkiller

    Battenkiller Minister of Fire

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    Well, then, it's good thing I stopped when I did. I saw I had one character left I could have put in the post without exceeding the forum limit. That one character just might have put you over the edge. :lol:
  16. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Well BK, I've had a few characters put me over the edge a few times but those days are past.
  17. Danno77

    Danno77 Minister of Fire

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    Cliff note me. Sounds like we need to make sure we are reporting our MCs in a way that specifies wet or dry method. MCD or MCW. And the meters we use give us the MCD, correct?
  18. Danno77

    Danno77 Minister of Fire

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    Sorry, premature send...

    ...annnnddd, when we aim for <20%, for example, that refers to 20% MCW, so if we are using a meter, it would be in our best interest to convert the MCD to the MCW using the formula provided.
  19. Flatbedford

    Flatbedford Minister of Fire

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    Or just forget the meter and make sure your wood is seasoned 2 or 3 years.
  20. Danno77

    Danno77 Minister of Fire

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    BK, I assume you have seen this. It has a great list of specific gravities for a LOT of different species. It also has some formulas for determining correction for species, discusses range within species, etc.

    http://tinyurl.com/3e4y9sk
  21. Todd

    Todd Minister of Fire

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    Very interesting BK, thanks for the analysis. I'm still sticking by the reliable liquid soap bubble test to find out when my wood is ready. Maybe you could tell us at what mc you can blow bubbles through a split?
  22. pen

    pen There are some who call me...mod. Staff Member

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    Pics or it didn't happen!

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  23. Battenkiller

    Battenkiller Minister of Fire

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    No need to do the conversion, really. Just accept that 25% on the meter is the "new 20%" and aim for that. If folks would just trust me on this one, there would be a lot less bandwidth used and Craig would be richer and could buy a bigger sailboat. Or trust EPA Method 28, which specifically states that test loads must be between 19% MC and 25% MC dry-basis.... that is, as the resistance meter reads after species correction. I really don't give a rat's rump about the claims some stove makers supposedly make regarding the MC of firewood in their stoves. If it burns fine at 25% on a meter during the EPA test, it burns fine in the stove period.

    You can all sort out for yourselves whether or not an extra 2-3 years to possibly squeeze out a few extra BTUs is worth it. I personally think it's a waste of time and space, but whatever blows yer skirt. It's a hobby for many... have fun stacking it. Not likely too many folks in the states can ever get it too dry for peak efficiency anyway, the EMC in their region will work against it.

    Yes, you still have to correct for species. Shagbark hickory reading at 28% on the meter is in reality at least three points lower. That means it is 20% MCW... yup, ready to burn. That Wagner manual is nice info, but it doesn't translate to electric resistance meters. The Wagners use RF waves to measure density only. Density is just a part of the equation with the resistance meters. Plus, the RF-type meters come with their own set of problems.

    Nice thing about the RF-types is that you could always oven-dry the wood without even knowing the species and then determine the density, but heck, if you did that you'd be almost all the way there for using the oven-dry method, which is foolproof if you can just weigh accurately and know how to use a calculator. I'd stick with the cheap little resistance meters, average the inner and outer readings to get an estimated average MC throughout the split, use the species correction table I provided for each reading, and burn it when it gets to 25% MC or less.

    Cliff Notes:

    1. You need to know the species of wood you are checking for.
    2. The wood is ready when it reads 25% on a resistance meter after corrections.
    3. Firewood usually has a moisture gradient. Add both corrected readings and divide by two.
  24. Todd

    Todd Minister of Fire

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    I thought I'd get banned for life if I posted pics! :lol:
  25. Danno77

    Danno77 Minister of Fire

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    Thanks for that, BK. I was just coming back to the thread to post my error, as I read the Wagner stuff, I realized it wasn't for pin-type resistance meters, but it was still interesting, lol.
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