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

Post in 'The Wood Shed' started by thinkxingu, Jan 1, 2010.

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  1. skyline

    skyline Burning Hunk

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    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..

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  2. Adios Pantalones

    Adios Pantalones Minister of Fire

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    "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 :)
  3. dave11

    dave11 Minister of Fire

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    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.
  4. Battenkiller

    Battenkiller Minister of Fire

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    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.




    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.




    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.




    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
  5. JerseyWreckDiver

    JerseyWreckDiver New Member

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

    Battenkiller Minister of Fire

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    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.





    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.
  7. Rockey

    Rockey Minister of Fire

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    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".
  8. LLigetfa

    LLigetfa Minister of Fire

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    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.
  9. LLigetfa

    LLigetfa Minister of Fire

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    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.
  10. Rockey

    Rockey Minister of Fire

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    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).
  11. Battenkiller

    Battenkiller Minister of Fire

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

    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.
  12. claudebo

    claudebo New Member

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    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
  13. DBoon

    DBoon Minister of Fire

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    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 http://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.
  14. LLigetfa

    LLigetfa Minister of Fire

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    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.
  15. iceman

    iceman Minister of Fire

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    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!
  16. Rockey

    Rockey Minister of Fire

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    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
  17. iceman

    iceman Minister of Fire

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  18. Rockey

    Rockey Minister of Fire

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

    Battenkiller Minister of Fire

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    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.
  20. savageactor7

    savageactor7 Minister of Fire

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    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.

    [​IMG]

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

    SolarAndWood Minister of Fire

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    Given whats in your bucket, you must have some big guns.
  22. savageactor7

    savageactor7 Minister of Fire

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    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.
  23. karri0n

    karri0n New Member

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    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.
  24. savageactor7

    savageactor7 Minister of Fire

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    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.
  25. karri0n

    karri0n New Member

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