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Thread: Greenhouse drying of roughed out bowls?

  1. #1

    Greenhouse drying of roughed out bowls?

    Does anyone know if a greenhouse will work for drying roughed out bowls?

  2. #2
    Join Date
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    A friend operates a solar kiln business. He uses plastic sheeting instead of glass but the principal is the same. Large, south facing, plastic wall catches sunlight. Stays 75 degrees warmer in the drying room than outside temps. Key is proper circulation. A couple fans do the job.
    "Folks is funny critters."

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  3. #3
    The question is a greenhouse not a solar kiln.

  4. #4
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    Quote Originally Posted by Trevor Rice View Post
    The question is a greenhouse not a solar kiln.
    There is not a lot of differance in the two, one is kept a little cooler than the outher. Keep good circulation so the moisture will exit.
    Bob

  5. #5
    Join Date
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    Hi Trevor!

    Welcome to the Family!

    I think that a greenhouse, the is set up to be warmer than the outside temps, would speed up the drying process, but I'm not sure that is a "Good" thing.

    With a roughed out bowl, I wrap them in brown paper, then expose the inside of the bowl, while keeping the outside wrapped, this idea is that the inside will dry a bit quicker than the outside. This is supposed to stop the roughed out bowl from cracking. If the inside surface shrinks a bit sooner than the outside, it will be held under pressure, and not crack, if the reverse were true, the outside would crack like crazy, as it would not have anything holding it in place, so to speak, or at least that is the way it was explained to me.

    What does this have to do with your "Greenhouse" question, well, I wonder if speeding up the drying process is a good thing or not

    I guess if you had the bowl wrapped, like I explained it would not make a difference.......

    I guess if the temp in the greenhouse was a bit warmer, that should cause the water to evaporate from the wood quicker, how much quicker, without out circulation is unknown, but if it was a fairly large green house, then I'd not worry too much about circulation, as the volume of air inside would be fairly great, and it would take a lot of evaporation to saturate that volume with enough water vapor to slow down the drying out process....I think...

    Sorry, not much help am I

    Hopefully this will spark some discussion, and we can answer your question better.

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  6. #6
    Join Date
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    A greenhouse can get very hot.

    On a sunny day, 80 degree day, the inside of a naturally ventilated greehouse can easily go well above 110 120, 130.....

    In the winter, on a sunny day, 30 degree day, the inside of a greenhouse can get up over 80 degrees easily.

    Joe

  7. #7
    Join Date
    Jan 2007
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    Would a greenhouse, actually being used as a greenhouse not be quite a bit higher in humidity than is necessary for drying wood? I'm thinking of early spring when we have our garden started under plastic (yeah yeah - we cheat ) and the inside of the plastic is covered and dripping with moisture from the plants - even when we have the ends open to keep the temperature down.
    Bottom line .... I don't know for sure, but I would be surprised if the wood would ever dry to the moisture content that you want it to if the greenhouse is in use as a greenhouse.
    If it's not in use as a green house, then it would be one fancy kiln!!

    cheers

  8. #8
    This is an interesting subject and one question I had to research when I started building my own Solar Kiln. I am not the authority on this, but I think a greenhouse and a kiln are similiar and yet different. At least that is what my research leads be to believe.

    The thing is, a greenhouse and solar kiln are operating on two different principals. A greenhouse is primarily built to elevate the temperature of the air inside the building and keep the plants cozy and warm. This is to trick the plants into thinking its Spring a lot earlier than it really is. Fans, vents and supplemental heating units accomplish this by keeping the TEMPERATURE even and TRAPPING MOISTURE.

    A solar kiln on the other hand is built to REMOVE MOISTURE from the wood, not heat it. Elevated heat drives trapped moisture deep inside of the wood out towards the outer portion of the boards where the heat around the wood wicks it away quickly and fans pull the moisture laden air outside and away from the lumber pile. You don't want this to happen 24/7 because that would dry the board too quickly and does not allow the board to equalize stresses deep inside it.

    Think of it like a sponge. If you toss a sponge onto a sunny deck in the heat of summer, the sponge dries into a hard lump in a deformed shape. But take that sponge, squeeze it a bit, let it dry, then squeeze it a little bit more and let it dry, and do that several times and it will be throughly dried and yet retain its shape.

    Now to get back to the original question, you cannot just throw a pile of wood in a greenhouse and expect it to dry out very quickly, or retain board like zen. But the good news is, you can use the basic greenhouse building and easily modify the fans, heating system and temperature control to control the moisture level and heat levels to dry wood.

    Basically you switch operating systems. With a greenhouse you run the fans during the day and use additional heat at night to keep the temp even. With a kiln you want the temp to warm during the day and cool at night to allow the wood to de-stress. Still you want any and all moisture to be removed from the wood and the building. Install a monitoring system for humidity instead of being temperature based, and you have a kiln.

    Probably very confusing in the written word because I cannot explain myself very good, but hopefully you can see what I am getting at.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  9. #9
    One more thing...if you keep the temp up over 150 degrees for 24 hours, you can kill all bugs, insects and larvae that may be in the wood. Some solar kilns (like mine in here in Maine) cannot do this without supplemental heat.

    One other thing...a solar kiln cannot over-cook wood like that of other kiln designs. Therefore a solar kiln makes a a great place to store wood as well. You get double-duty from it really. Drying and storage.
    I have no intention of traveling from birth to the grave in a manicured and well preserved body; but rather I will skid in sideways, totally beat up, completely worn out, utterly exhausted and jump off my tractor and loudly yell, "Wow, this is what it took to feed a nation!"

  10. #10
    Join Date
    Dec 2006
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    Quote Originally Posted by John Bartley View Post
    Would a greenhouse, actually being used as a greenhouse not be quite a bit higher in humidity than is necessary for drying wood? I'm thinking of early spring when we have our garden started under plastic (yeah yeah - we cheat ) and the inside of the plastic is covered and dripping with moisture from the plants - even when we have the ends open to keep the temperature down.
    Bottom line .... I don't know for sure, but I would be surprised if the wood would ever dry to the moisture content that you want it to if the greenhouse is in use as a greenhouse.
    If it's not in use as a green house, then it would be one fancy kiln!!

    cheers
    Water management will keep humidity levels lower. Also, watering the plants in the morning and allowing them to dry out in the evening would minimize condensation.

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