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wood drying - acclimation - Bill, Tindall, please

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wood drying - acclimation - Bill, Tindall, please

#1

wood drying - acclimation - Bill, Tindall, please

Bruce, a MN Galoot

>Bill,

I can't seem to find your treatise on drying wood, but the way I understand it, properly dried wood is KD to about 7% and then steamed or at least humidified to a higher % and then allowed to sit before final drying. This is to remove any casehardened stress that results from the initial drying. Correct so far?

Okay, here's my question: I get some pretty decent and economical (cheap) wood from a local sawyer who KD's the wood to about 7%. If I then take that home and let it sit in my garage in MN for a couple seasons (and the resulting humidity cycles you know so well) will that elapsed time alone help deal with any potential casehardening, or is this something that has to be done deliberately? I guess what I'm doing is air drying some already kiln dried wood.

Thanks.

Bruce, in curiously mild MN.

Re: wood drying - acclimation - Bill, Tindall, please

#2

I'm not 100% sure......

Scott in Eastern Iowa

>.....but I think its to late to "unset" wood thats already been casehardened. My understanding is once its done, its done...no reversing the situation is possible.

I think Bill can relay that the introduction of heat or steam while kiln drying is really conditionng the wood to dry correctly.

Im now curious to hear if casehardening can be reversed myself?

Others?

Re: wood drying - acclimation - Bill, Tindall, please

#3

Jim in Burlington Ont.

Case hardened

Jim in Burlington On

>I bought some lumber that was case hardened it twisted and warped when it was skip planned so badly that it was fit for firewood. I asked the seller and he said it was not possible to fix. I've read that vacuum drying eliminates that problem.

Re: wood drying - acclimation - Bill, Tindall, please

#4

no

BT, E. TN

>Wood is only plastic when it is hot and wet, as we all know because this is how it is bent. To relieve kiln drying stress, or any other stress, or bends and warps for that matter, the wood needs to be hot and wet. An injection of steam at the end of the cycle accomplishes this benefit, at least at the wood sruface. Alternatively, at the beginning of the cycle when the kiln is hight humidity any air drying stress will be removed.

Re: wood drying - acclimation - Bill, Tindall, please

#5

wrong

BT, E. TN

>"I've read that vacuum drying eliminates that problem. " Not correct. Too fast drying causes the problem. It can occur even in air drying, or any other drying that happens too fast.

Re: wood drying - acclimation - Bill, Tindall, please

#6

Darn!

Bruce, a MN Galoot

>

Re: wood drying - acclimation - Bill, Tindall, please

#7

clarification

bill tindall, E. TN.

>Any process that provides better control of the drying process will provide the opportunity to more easily avoid drying induced stress (case hardening and the like). So, vacuum drying and dehumidification kilns drying lumber that has not been air dried in an uncontrolled fashion can produce stress-free lumber. But, so can a properly operated convention steam heated kiln. Stress-free lumber is most dependent on the skill and experience of the person running the kiln and management's attitude toward producing a quality product.

The only commercial operation I have seen doing vacuum drying was a small operation drying expensive-wood turning squares.

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