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Moisture and does wood dry in sub-freezing temps?

Post in 'The Wood Shed' started by OldLumberKid, Jan 18, 2013.

  1. OldLumberKid

    OldLumberKid Feeling the Heat

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    So, it's a bit below freezing outside and will get to 15 F at night next week ... is my firewood still drying at 30F on a strlit night, or does that freeze lock the moisture inside the wood? Or, does the freezing cold wind still "dessicate" the wood no matter what? I think I know the answer, but I trust you experienced firewood-heads out there better than my intuition.

    My guess is the colder it gets near or below freezing, the more that moisture simply crystallizes inside the wood, and does not dry ... except at the surface where it is dessicated or dried by the wind, and whatever moisture is thawed during warmer periods of time, and able to move toward the surface as a result of capillary action.

    I'm guessing freezing winters don't do much for drying. The only thing that tells me I'm wrong is my dry skin and my lips — but then they are living warm and moist entities meeting cold and dry wind — not dead frozen entities with moisture frozen inside them.

    OK ... I'm done theorizing ... have at it men and women of the woodshed, what's the deal?

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  2. billb3

    billb3 Minister of Fire

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    you could always freeze-dry your wood to speed up that slow sublimation process
    OldLumberKid likes this.
  3. Mr A

    Mr A Minister of Fire

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    i'm no scientist either, but I think your theory is correct. That wood will not dry until it thaws first. I see it as trying to thaw an ice cube in the freezer, just not going to work
    Shane N and OldLumberKid like this.
  4. Paulywalnut

    Paulywalnut Minister of Fire

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    Humidity plays a big part in the drying process.
    It can be very cold with low humidity. Wood
    that has been css for a year will still be drying out
    in 15 degree weather. IMO of course;)
  5. Jon1270

    Jon1270 Minister of Fire

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    Moisture does leave the wood even at low temperatures, but it happens much more slowly. The rule of thumb is that wood dries about twice as fast for every 20-degree (Fahrenheit) increase in temperature. So, the drying rate at 30F is about a quarter of the rate at 70F. Wood actually contains natural antifreeze, so free water in the cells doesn't freeze until it gets much colder.

    Here's an interesting discussion. Pay attention to Gene Wengert's comments; he's Professor Emeritus at the University of Wisconsin-Madison, taught at Virginia Tech, worked for the US Forest Products Lab and had a hand in the research for and writing of a lot of government publications on wood processing. He's not guessing.

    I have a bunch of black locust that I scrounged in early December, and as an experiment I've been regularly weighing a particular split (initially about 10 pounds) that's been on the top of the stack. Even with being rained on and then sitting in a pile of snow, it has shed about 10 oz. in the last month or so.
  6. Gark

    Gark Minister of Fire

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    Sublimation of water ice must happen at least a little bit. Same thing that shrinks ice cubes in your freezer and makes chunks of ice outdoors slowly disappear.
  7. ScotO

    ScotO Guest

    Sublimation, gark is right. Now granted it will NOT dry like it would on a warm, breezy day. But if you go out on a really cold morning and the sun is coming out, when it starts beating down on the frosty roof of your house you can see 'steam' coming off the roof.....that's actually sublimation....

    It can and will season in the freezing cold, just not neartly as fast as in the warm breeze.
  8. cygnus

    cygnus Feeling the Heat

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    As water freezes it also expands. My theory is that the freezing and thawing expands and contracts the cells and allows moisture to better evaporate when it can. I wonder if split dries faster after a few of these cycles compared with one that never freezes. Also makes me wonder if it's part of the reason for the term 'seasoning'. Again, just a theory.
  9. Backwoods Savage

    Backwoods Savage Minister of Fire

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    When it gets real cold it also usually has a drop in the humidity levels. Yes, wood will dry in the winter but as stated by others, not as fast as it will in the summer.
    OldLumberKid likes this.
  10. rideau

    rideau Minister of Fire

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    So, if our average sumnmer temp was over ten degrees warmer than usual, and for a much longer time, then I really got about 1 1/2 to 2 years of drying compared to normal? So, at what temp does oak take 1 year, at what temp 2 years, at what temp 3 years to dry?
    ailanthus and OldLumberKid like this.
  11. OldLumberKid

    OldLumberKid Feeling the Heat

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    Lot of great replies and fun replies,
    but thanks for the standout info here, Jon.

    I've got one son who's good at splittin' and one who's getting better at math. I may ask the kid who's doing well at math to see if he can figure that one.

    You also just reminded me we have a few more rounds to split before all the Sandy wood we've gotten to date is CSS'd
  12. BobUrban

    BobUrban Minister of Fire

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    Simple answer, Yes - for all reasons stated above. This is what(or a significant part) of what causes freezer burn. And as many who know the bummer of a poorly packaged backstrap with freezer burn looks like - Arggg!! It burns from the outside in because of moisture accessability so I am sure wood in your stacks reacts the same. Venison wrapped tightly with plastic wrap last almost indefinitely so keeping air off the wood slows that process.
    Backwoods Savage likes this.
  13. Cross Cut Saw

    Cross Cut Saw Feeling the Heat

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    I moved to Maine from Boulder, Colorado and at the time I had never had a fireplace or stove and had no idea wood needed to season.

    I would assume that wood in Colorado dries at easily twice the rate it does in Maine. With 300 days of sunshine, summer days often in the high 80's and low 90's, humidity in the low 20%-30% range and warm spells in the middle of the winter that can reach 50 degrees for days on end it must be a wood drying paradise!

    I have noticed my wood seasoning this winter here in Miane, even with the sides slightly covered on my stacks they've been slowly losing moisture, slowly...
    Backwoods Savage likes this.
  14. oldspark

    oldspark Guest

    Another subject that comes up ever year, there is two types of water in wood, free and bound and if I remember correctly the free water is lost below freezing temps and the bound water does not, so the right answer is yes it drys in the winter but not as complete as summer.
    This is a common sense statement from another site.
    "One of the reasons wood does not dry as well in the winter (at least in climates that have a "real" winter) is that the moisture does not move very well through the wood when it is below freezing. So any drying tends to be surface drying, and not as much gets drawn out from the interior of the wood."
  15. OldLumberKid

    OldLumberKid Feeling the Heat

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    Thanks oldspark, and apols for the newb question — I'm sure with each year that passes there are new folk who have new things to add — but so many interesting answers here including yours. Gotta love the knowledge and experience of the folk here. It seems the more you ask, the more you learn.
  16. cptoneleg

    cptoneleg Minister of Fire

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    I like to think that the moisture in the wood freezes and expands and cracks the wood and helps the drying process, even more when warm weather gets here. Each season has its purpose- thus we have seasoned wood.

    Thats Country for Yes
    OldLumberKid likes this.
  17. oldspark

    oldspark Guest

    I'm still learning too, I used to think it did not dry at all in the winter period until battenkiller informed me different, so ask away cause some times we all learn something.
  18. dave_376

    dave_376 Burning Hunk

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    yes it will dry some in the winter, not as rapidly as 90 deg heat in full sun with a steady breeze but something is better than nothing. I remember thinking my mother was crazy hanging cloths on the line in the dead of winter. if you touched them an hour after they got hung they would be frozen stiff. At the end of the day she would take them in and they would usually be dry, some things like jeans would still be damp but alot of it would be perfectly dry.
    Backwoods Savage likes this.
  19. rideau

    rideau Minister of Fire

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    I've ben known to do this. It's awfully hard on the hands...
    Backwoods Savage likes this.
  20. OldLumberKid

    OldLumberKid Feeling the Heat

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    ADDENDUM: Now that the wood has thawed out ... the inside of the Oak has changed color back again from frozen gray to beautiful red. Just goes to show what the freeze does.

    [I'll update moisture readings when I'm recovered enough post-operatively (laparoscopic internal organ removal) to split a split. .. Don't hold any breath it could be a week or two. No heavy lifting of any kind right now]
  21. bogydave

    bogydave Minister of Fire

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    This wood was green, CSS in Oct & has been below freezing since I stacked it.
    Cracking, splitting & drying at sub freezing temps.
    Not sure how much, should weigh one some Nov & then in May when it thaws.

    IMO wood dries thru winter here. It does dry slow though ,
    it's hard to wick the inside frozen moisture to the edges,
    Low humidity with cold temps.

    DSCF0747.JPG
    OldLumberKid likes this.
  22. OldLumberKid

    OldLumberKid Feeling the Heat

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    Slow or not, that woodpile looks darn purdy as a picture, like it was assembled by a zen master or a trained dry-stone wall builder. lol. Fine handiwork there.
  23. bogydave

    bogydave Minister of Fire

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    Wife stacked this section
    Slow & meticulous , but was glad to have the help. ;)
  24. PapaDave

    PapaDave Minister of Fire

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    Dave, I've got some Maple and Oak I put up last Oct. through Dec. that looks quite like that.
    It gets a lot of sun and wind......well, as much sun as we get in the winter.>>
  25. tsquini

    tsquini Minister of Fire

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    I like this question. During winter the dew point and relative humidity is low which means there is very little moisture in the air. This is why we get dry skin and lips. This is the same reason why a block of ice out in the cold it begins to shrink in size without melting. The dry air is pulling the water out of the block of ice into the air. This works the same way with the water content in wood. In dry air pulls the moisture out of the wood. Warmer weather has higher humidity, which makes it harder for water to evaporate in the air. But warm weather also allows the water in the wood the make its way to the surface. Which dries faster, warm or cold weather. I do not know. I'm sure there is a gold ratio of humidity and air flow that work equally as we'll in both cold and warm weather.

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