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Air dried vs. kiln dried

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Forum topic by thedudeabides posted 10-22-2009 03:33 PM 6278 views 0 times favorited 10 replies Add to Favorites Watch
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thedudeabides

75 posts in 2600 days


10-22-2009 03:33 PM

I’m still at the stage where dried wood is dried wood. Can anyone explain the various nuances of air dried stock vs. wood that’s been kiln dried? Is one preferable to the other?


10 replies so far

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Timberwerks

355 posts in 2621 days


#1 posted 10-22-2009 03:49 PM

I prefer air dried for it’s color and the way it works. Air dried Walnut for example has better color then kiln dried. My work is mainly done by use of hand tools and I find that air dried does work better than kiln.

-- https://www.facebook.com/pages/Timberwerks-Studio/126415221682

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PurpLev

8523 posts in 3108 days


#2 posted 10-22-2009 04:04 PM

think of a car breaking:

air dry = car breaking easily over a long distance
kiln dry = car making a sudden emergency stop

both cars are standing in place at the end. one has comfortable mellow people, while the other has stressed people in it (and boxes/bags/drinks/other all over the place).

this analogy may be on the extreme side of things – but generally speaking – these are some of the differences between air/kiln dry processes. kiln dry wood may have more internal stresses in it. in some cases, this may not be noticeable, and doesn’t necessarily means it’s worse for general use. it is however faster to get the wood to dry that way.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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Moron

5032 posts in 3353 days


#3 posted 10-22-2009 04:05 PM

the best thing about KD wood…............is that its dead and anything in it is dead, like those nasty powder post beetles that can take a beautiful home and turn it into dust.

I kinda doubt that AD walnut, red and white oak, pine or any other kind of wood looks better in colour then KD….....

having a sweet collection of AD wood I re-claimed from an old church that was torn down and knowing that the wood air dried for almost 200 years…...............its very nice, very nice indeed and it only took 200 years to dry.

-- "Good artists borrow, great artists steal”…..Picasso

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IkeandBerry

45 posts in 2724 days


#4 posted 10-22-2009 04:10 PM

I prefer the air dried lumber as well. You will need to let is set in your shop for a few weeks so that it can adjust to the new environment. Also it is not as dry as kiln dried so it may change more season to season than kiln dried. i use mostly hand tools and air dried lumber is much easier to hand plane especially when you are working with oak. I have also found the color to be superior. There are also new kilns called sola kilns that are low temperature kilns. They produce kiln dried wood that maintains the look of air dried wood. Good luck.

-- There is nothing like the sound of a hand plane passing across a board in an otherwise quiet shop.

View gerrym526's profile

gerrym526

266 posts in 3268 days


#5 posted 10-23-2009 12:08 AM

There was a recent article in Fine Woodworking on how to air dry lumber. A number of the contributing authors-all expert woodworkers-were quoted as saying they prefered air dried lumber for its color, workability, etc.
The primary reason for kiln drying is that it allows the hardwood lumber industry to “short cut” the drying process and get the product to the woodworking market more quickly. A huge downside to kiln drying is the problem of “case hardening” which is where the wood gets very brittle after being subject to heat. I had a problem with a big order of red oak for a project. The case hardened wood pulverized when I tried to cut tenons from the stock.
Air dried lumber is the choice.

-- Gerry

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Catspaw

236 posts in 3275 days


#6 posted 10-23-2009 01:29 AM

1 year per inch.

Too long for a lumber company.

Once wood is dry…it’s dry. Letting it sit in your shop allows it to settle (from general humidity as opposed to tree juice moisture). You’ll build your piece….everything is nice and square…joints are tight, etc. etc…...then once it goes out the door and into a different environment…nothing you did will matter…as it will be subject to the environment it is put into. At least the doors didn’t stick when you built it.

Don’t know about color as we use so much walnut. I built my kitchen with my dad’s air dried walnut (some 15 years or so.) The stuff we get from mills is always steamed. Mine looks alot better than the mill stuff. And spalted maple is probably better KD so the microbes don’t keep munching on the stuff we make.

-- arborial reconfiguration specialist

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HokieMojo

2103 posts in 3188 days


#7 posted 10-23-2009 02:45 AM

air dried
better color
wood is subjected to less extreme temps
potentially less checking
lower cost
less brittle material
less volume constraints (only so much can fit in a kiln at once)

kiln dried
pests are killed (like beetles and termites)
fungus can be killed (helpful for special woods like holly)
faster dry times
more control over the rate of drying
lower moisture conent is possible which is beneficial for indoor projects

View bandman's profile

bandman

79 posts in 2850 days


#8 posted 10-24-2009 03:45 AM

Air dried lumber is typicaly left outside under cover in the natural environment stickered and left out of direct sunlight. Depending on where you are located, air dry moisture contents will vary based on the relative humidity of your region. In Wisconsin, air dried is typically between 13 to 16 percent moisture content in
the wood. Lumber will come off of a sawmill at varying moisture contents between 20 and 40 percent MC
depending on species and environemnt. Once hardwood lumber is air dried, it can be taken into a controlled
environemnt and it will finish drying and stabilize over time. Typically in colder climates air dried lumber and allowed to stabilize to 6 to 8 percent MC over a period of about 4 to 10 weeks indoors in the heating season.
At this point, the material is essentially the same (moisture content wise) to a board you purchase that has been kiln dried. Kiln drying wether covnetional or dehumidification drying speeds up this process under controlled conditions with the main difference being time in which the lumber dries. If you use air dried lumber and want to be sure of its moisture content before proceeding with your project, check its mc
with a moisture meter.

Kiln drying over a very short period of time at high temperatures can produce residual stresses and case hardening in the lumber if it is not properly controllled/operated during the kiln drying process, or too much moisture is removed from the lumber too quickly.

In my experience, air drying can produce different colors and hues in woods, especially in black walnut
material that generally contains white sapwood and darker black heartwood. Often when walnut is dried in
a conventional kiln the lumber is steamed which effects the color and appearance of both the heartwood and the spawood in black walnut.

HokieMojo above does a good job of summarizing the key differences above.

Also, keep in mind when you purchase a 2×4 at a local lumberyard when you purchase it is considered construction dry (air dry) at 19 percent MC or less for residential construction. Typicall MC for hardwood for funiture production is quite a bit dryer than this lumber typically is.

-- Phil

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a1Jim

115201 posts in 3037 days


#9 posted 10-24-2009 04:03 AM

I use both

-- http://artisticwoodstudio.com Custom furniture

View Moron's profile

Moron

5032 posts in 3353 days


#10 posted 10-24-2009 06:39 AM

AD and KD is liken to good cheese and bad cheese, good wine and bad wine, good scotch and bad scotch.

Good Cheese is a year old…......really good cheese is 10 years old….some say processed cheese slices isnt really even real cheese yet we all eat it.

Fresh Bacon isnt as good as double smoked bacon yet if you super heat either one too fast, for too long they dont taste very good.

Some folks can wait ten years for a good chunk a cheese and enjoy it with a fresh wine….some cant wait for an old wine to age and enjoy with a new cheese…....

My point being

You will not find an impartial view on KD vs AD because there isnt a simple answer.

-- "Good artists borrow, great artists steal”…..Picasso

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