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Thread: Kiln dried wood characteristics

  1. #1
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    Kiln dried wood characteristics

    During recent family visits I discovered that 2 of my cousins operate sawmills separately. One of them also has a kiln, I think he said that 7% moisture is the usual target.
    What happens to wood when it is kiln dried?
    He said that the windows in the original farm house, 100 plus years old are still good, but the ones in an addition that is only 60 years old had to be replaced. He blamed the early demise of the new windows on them being made with kiln dried wood.

  2. #2
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    Paul, I use a kiln that I built for drying all of my roughed out bowls and so on. I don't use a moisture meter as I seem to always manage to ruin them somehow. But, what I do is before I put something in the kiln with pencil I write on it somewhere the wood, date, and weight. The weight is the key thing for me. I usually see them lose about a third of their original weight. Also, to reduce checking drastically in the kiln I oil the piece down with walnut oil, the same I use the seal the finished product before finishing. I use 5 125 watt brood lamps for my heating. Depending on the weather determines how many I have turned on. I like to keep it at about 110 degrees. Some run theirs kilns hotter than that but I don't find it necessary. I know two very successful furniture builders and they use kiln dried wood for all of their work from tables to chairs. I don't think the early demise of the wood you mentioned is from them being kiln dried. I could be wrong. But to me if you want any wood to last it has to be maintained. Anyway, I don't know if that helps you or not.

  3. #3
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    Paul, Wood will acclimate to the environment in which it resides. If 7% kiln dried wood goes into a house in which everything is at 11%, then that wood will eventually stabilize at 11%. I'd be more inclined to look at the quality of wood in the 100 plus year old windows versus the quality of wood in the addition. Perhaps old growth tight grained, properly oriented and possibly hand crafted material lasted longer than mass produced stuff made with any old quality wood?

  4. #4
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    I have a question, if the wood still has moisture and you stabilize
    The wood will it remove the moisture as well as the air
    I dream a lot. I do more painting when I'm not painting. It's in the subconscious.
    ::: Andrew Wyeth :::
    colonialrestorationstudio.com

  5. #5
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    My cousin said that an old timer told him that kiln drying the wood causes some cellular changes, but I can't remember the details. These changes don't happen if the wood drys slowly over a number of years.

  6. #6
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    From what all I know about drying wood is this. Whether you do it in a kiln or let it dry out over the years, there are cellular changes going on regardless. Anytime the moisture in the wood's cells is moved or dried out it is a cellular change. Again, makes no difference how you dry it. Kiln or time. I have been using a kiln for my roughed out pieces for about 8 years and have no problems. Kilns offer wood turners and wood workers a viable option for preparing wood to work with that has been used for a long time. Some folks don't like them because they think the process is not natural or "pure". Anyway, I use one, and in fact I am working up the plans to build me a new and better one. I have a friend who is very successful in furniture building and his kiln is a 40' long metal box trailer modified with a propane heater rigged in it with rolling racks for the boards. I don't need anything like that.

  7. #7
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    I just place mine on racks in front of the big heater upstairs , dries out quick.
    I dream a lot. I do more painting when I'm not painting. It's in the subconscious.
    ::: Andrew Wyeth :::
    colonialrestorationstudio.com

  8. #8
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    That's almost a built in kiln, Dave! Good idea. I'd do that as well if I have that here. Oh, well. So, I build a kiln. Nothing fancy, but it works.

  9. #9
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    Quote Originally Posted by Paul Brubacher View Post
    My cousin said that an old timer told him that kiln drying the wood causes some cellular changes, but I can't remember the details. These changes don't happen if the wood drys slowly over a number of years.
    He was probably talking about something like this - "Quality Control in Lumber Purchasing: Lumber Stress/Casehardening"
    https://www.extension.purdue.edu/ext...NR/FNR-132.pdf

    This can happen with air drying (for example if you put wet wood in a really arid and windy place), but its less common.

    I'm dubious that the window failure was due to kiln drying as well. My guess would be that the older windows were more heart wood.
    Compare the longevity of heartwood vs sapwood in the long term post durability study here, its definitely significant:
    http://www.fs.fed.us/eng/bridges/doc...p/decayres.pdf

    Its also possible:
    • That the old windows weren't pine at all but were cypress or something similar (or a different species of pine) that has much better durability.
    • That the old windows were better made and the new ones or the casement for the new ones didn't account for water movement as well. Sometimes there are devils in the details here.
    • There was some other cause we're not considering and it would be hard to know without doing a full forensic analysis and even then many things we'd be guessing on.

  10. #10
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    Thanks Ryan, those are interesting articles.
    Unfortunately they don't mention in the paper on wood durability how the wood was prepared.

    What was the moisture content, was it air dried or kiln dried?

    Did they use galvanized nails?

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