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Any Difference Between Air Dried And Kiln Dried?


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I just wanted to know if anyone likes air dried or kiln dried wood better? I don't know of any differences but I sure someone with a lot of experience would. The only piece of air dried wood I have ever got had a very slight bow in it, and all the kiln dried wood I've got has been straight as an arrow. It might just be coincidence I'm not to sure. Also I know there are many variables pertaining to this subject like if the wood was laid flat and type of wood, but I am just looking for a general idea. I'm sure there are a few of you out there that have some knowledge of this, maybe Rich, I know you see a whole lot of wood. I think most wood that I see and probably most people see is kiln dried though.

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smilie

Thanks for the help! Jason

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well, here's my two cents worth...it's all about the moisture content. if a board has been air dried properly to say 6 or 7% moisture it should be just like a kiln dried board with the same content.

as far as bowing goes i've been in the building trades for many years and most commercial lumber is kiln dried. i've seen some wood so bowed it didn't even make good firewood. i believe hardwoods like you would purchase for a guitar are dried slower and longer and are less likely to bow.

and you're right..most of the wood we use around here is probably kiln dried. but i have friends around my town that slab out large cypress and pecan that fall and air dry them for mantles and counter tops and such. after they slab them out they'll usually coat them with linseed oil to retard drying and thus avoid too much checking. i've been the fortunate recepient of quite a bit of their leftovers and have made some beautiful guitars from them.

so to me it seems it's all about the care taken in drying the wood no matter which way it's done.

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I'm not really sure that a lot of the reported differences aren't mythologies. Wood dried to 7% shouldn't perform any differently no matter how it gets there.

That said, James Krenov, who is one of the heavy hitters in contemprorary funiture design, feels that there is a very noticable difference in the appearance of air dried lumber. Most of the folks who post here seem to use a lot of heavy stain colors and/or colored finish so it isn't as noticeable as on minimally stained and oil finished furniture, which is what Krenov favors. Check out his book "The Improbable Cabinetmaker" sometime. He addresses a lot of the generic techniques common to all woodworkers and is a pretty interesting author.

I've noticed a little difference in air dried cherry and walnut, especially if you finish with blades rather than sandpaper. Chisels, planes and scrapers seem to just leave a cleaner, clearer surface with air dried lumber. May be just wishful thinking but it does seem to look a little better. I've used some air dried hickory and pecan an seat-of-my-pants felt that the weren't quite as brittle as the kiln dried stuff.

It does take a long time to air dry rather than kiln dry. The last walnut I had anything to do with stayed in a friends oven like attic for three years before it was usable, and this was rough cut to 6/4.

The most important thing with any lumber if you are concerned with long term performance and flatness is to stick it with a moisture meter and make sure of the content.

It also helps to dress your stuff to size and let it sit no matter how it was dried. Put "sticker" boards under everthing so that the air can get around all sides, and let it rest for a couple of days to a couple of weeks so that the moisture is even throughout. This is expecially true with the really thick 8/4 stuff.

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Kiln dried anything doesn't need the preparation that air dried does. If it is going into a steam or microwave kiln it is usually just shoved in there. To properly air-dry, you have to seal the ends for the long term. Air-dried tends to have a lot more end-splitting than kiln. When you find a nice, unsplit piece of air-dried, you found a nice piece of wood. It be happy.

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It's all about the internal stresses.

People who champion air dried argue that the wood loses moisture at a slow and varied rate. As the wood is drying, the weather changes, so the moisture loss is always fluctuating i.e. the wood loses a little moisture during the day, then gains a little at night, loses a little during hot days, gains a little during rainy days etc. This allows the core moisture content to catch up with the skin moisture content and in theory should reduce the internal stresses to the bare minimum.

Modern kilns try and duplicate this at a faster rate.

We use a lot of hard maple from North America and a lot of bubinga from Africa. The maple is pretty predictable, the bubinga moves around a little more after it's cut. This could be directly related to the properties of the wood or it could be that kiln technology is better in North America. We had a couple hundred bft of pau ferro that was extremely case hardened. It was perfectly straight in the rough, but when we tried to re-saw it, it cupped and bowed so bad that the last 1/8" would crack and break off before the saw had a chance to cut it.

Edited by ddgman2001
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The blank of air dried maple I have still has the ends sealed on it. Should I leave this sealer on throughout the shaping process? Will it help protect it from any future problems? For a soft maple neck blank size board is a little over a year not long enough for proper drying? I will probably get a moisture reading before doing any cutting, as this piece has really nice figure and will make for a great laminate with another very hard wood, like Jatoba or purpleheart. For being a red maple blank, not big leaf, it is very sturdy and stiff, much more than I was expecting. Maybe I got lucky with this piece being that most people have trouble with the softer maples.

Thanks for the very informative information! Please if there is any more, be sure to let me know! Thanks again!! Jason

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No! Cut it as close to the finished size as soon as you start. That way you will know if it is going to give you splitting problems up front. Heartbreaking to get down to the final shaping and have a bunch of uglies show up at the party.

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One year, per inch of thickness, to air dry woods. If its not stickered and waxed properly, you'll be in for grief.

I buy all my wood kiln dried, and store it for 12 months or more anyway. Im buying timber now for guitars that will be started in Dec 2006. Wood is cheap, you should do the same. Read up on wood storage, its all important.

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Rhoads hit the nail on the head. Wood needs time to adjust to the moisture levels in the area it is stored. The end grain will gain and lose moisture faster than the other surfaces so you seal it to stop the rapid changes. Air or kiln really makes no difference if it has stabalized. The problem with air dried is it usually is not done stabalizing. Same could be said of kiln if it has been subjected to rapid changes in moisture levels. If you cut a piece count on some movement if it has not had a sufficient amount of time to adjust to your area. Well dried wood may move and then basically flatten back out if it was dried pretty well, just let it settle for a few days. If you are moving the wood and it is a very hot or rainy day, it is a good idea to try to protect it by sealing it up in some plastic wrap.

I guess thats my 2 cents, Give it time to adjust. Oh yeah, don't store wood in a place that is extra dry. Just store it in area that is very typical of your area in terms of humidity.

Peace, Rich

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Not usually the case with kiln. It is more rapid, but more controlled. Most of the time the splitting happens at the end grain where the wood is more effected by rapid changes in moisture levels. Since air dried takes longer it will be subjected to more fluctuations over the drying period. Proprely maintained air dried is great.

Peace, Rich

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