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Wet wood and green wood, what is the difference?

Post in 'The Wood Shed' started by Jerry_NJ, Sep 14, 2009.

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  1. Jerry_NJ

    Jerry_NJ Minister of Fire

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    It is my belief/understanding that well seasoned wood that gets soaked by rain or melting snow, say, is still quite "burnable". That is, the water will have to be boiled off before the wood can burn, so some heat is lost to boil water. But, when the water is boiled off we have again seasoned wood in the fire.

    Green wood has moisture as part of its molecular make up, from growing. Here too, this moisture has to be boiled away before the wood can burn and thus heat is lot, but worse, the green growth water also has other affects - perhaps it lowers the temperature of the combustion of the wood itself, causing the combustion products to contain unburned wood products, i.e., creosote.

    Anyone got the answer?

    My use of the information is on handling wood that accidentally got wet while being stored outside. I try to keep seasoned wood dry, but if it gets a little wet, I will still use in the belief that if I keep the fire box hot, there is no significant increase in creosote emission due to the wood being wet.

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  2. Ratman

    Ratman Feeling the Heat

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    Your wet wood dries in weeks.
    Green wood needs to be split and dries in months / years.
    Only burn dry wood.
  3. smokinj

    smokinj Minister of Fire

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    if its just wet it will dry in a couple hrs. (already season)
  4. LLigetfa

    LLigetfa Minister of Fire

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    Seasoned wood that gets wet, only does so near the surface. It is still dry in the middle. Green wood is wet all the way through.
  5. gibson

    gibson New Member

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    Stack a cord of green wood then stack a cord of seasoned wood that is wet. No comparison. I will have the ice pack on my back after the green wood not the other stuff.
  6. Jerry_NJ

    Jerry_NJ Minister of Fire

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    Thanks I had a couple of cords of well seasoned hardwood that had not been stacked yet. It has a two day 3" rain that ended last night. I started stacking and will cover before the next rain. This was what got me wondering.

    So, it seems wet wood and green wood are both wet, but seasoned wet wood will dry a lot faster, in the air or in the fire. In the past I have thrown a split or two in a hot stove (insert) and all seemed well, the split would light and start burning in a few minutes, presumably after the moisture was driven off/out.

    I do plan to continue to protect the firewood from water. In NJ I don't start burning until November, so the subject wood has a couple of months to dry from the just passed rain.
  7. eernest4

    eernest4 New Member

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    put a top cover only on the wood pile & let the air blow in thru the ends & sides. single stack only with air spaces between stacks. If it is wet but seasoned, it will be ready to burn in a couple of weeks.

    stacking wood about 5 or 6 ft from the stove will dry off wet wood in a week or two & I always do this throughout the winter, although I do use the wood as required without respect to the drying time as I just take wood off the top of the pile to burn. But the wood at the bottom of the pile, if & when I finally get down to there, is some choice burning wood, let me tell you.
  8. Bigg_Redd

    Bigg_Redd Minister of Fire

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    All green wood is wet, but not all wet wood is green.

    Green = fresh dead
  9. jebatty

    jebatty Minister of Fire

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    You are correct, green wood also has water bound up in the molecular structure of the cells. It takes more energy to release the bound water, therefore longer to dry or longer to burn ... and heat energy is consumed to evaporate and release the water. It gets a little more complicated than that at the chemistry level, as for some woods it takes a lot more energy to release the bound water than for other woods, hence longer drying time.
  10. firefighterjake

    firefighterjake Minister of Fire

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    I think you've pretty much got the terms right . . .

    Green wood = fresh cut wood that hasn't seasoned (or dried out) -- the moisture content of the wood's interior is still pretty high. Not good for burning.

    Wet wood = wood that is wet from being in the rain or snow -- only the exterior of the wood is wet. This wood will be ready to burn in hours . . . or if you're willing to lose some BTUs and have a less than optimal fire for a few minutes can be put right in the fire.
  11. stejus

    stejus Minister of Fire

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    For those that don't believe wood that's been rained on will dry. Look at other wood structures subject to rain, (i.e. decks, siding, other structures). They are soaking wet during the rain event and dry within a couple of hours after rain, especially if it's sunny and windy. Wood absorbs water on the surface during a rain event, not the core.
  12. dvellone

    dvellone Feeling the Heat

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    I've suspected that when I've burned green wood the creosote buildup was greater than when I've burned wet wood.
  13. Backwoods Savage

    Backwoods Savage Minister of Fire

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    Don't expect creosote from seasoned wood even if it does get rain or snow on it.

    You are correct that when you start a fire or reload a stove, the moisture has to be burned off. In seasoned wood, that is 20% or less. In green wood it may be over 40%. If you have good seasoned wood and you get 3" of rain on it, the rain won't penetrate the outer layer. It is like your roof. The roof dries fast and so will your wood because it is only surface moisture, not like green wood that has the moisture all the way through the wood.

    Get the wood stacked and let the wind blow through the pile. Cover if you wish. We won't cover ours until November or December and that is wood that was cut last winter. It won't be burned for another six or seven years.

    Good luck and keep warm.
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