# Air dried vs. kiln dried???



## stinnettjn1 (Aug 18, 2011)

Just wondering as a newer inexperienced woodworker, is kiln dried lumber a must when building indoor furniture? The wood types I'm most curious about are walnut, maple, oak and pine. I found a local guy selling rough cut hardwoods that are only air dried (2 yrs) but I'm afraid the wood will move to much for furniture making.

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## jaxonquad (Jan 26, 2011)

A well respected fella here (Daren) has plans for an inexpensive, and effective dehumidification kiln. Why risk all that hard work your gonna put into your furniture?

: )


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## ed_h (Dec 1, 2010)

You'll probably get a lot of strong opinions on this, many based on hearsay, folklore, and maybe religion.

I've used quite a lot of both, and in my experience, once wood reaches a moisture content in equilibrium with its surroundings, there isn't any difference in how it behaves dimensionally.


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## Brink (Nov 22, 2010)

The only thing I've heard, and I never went about proving, is that kiln dried wood is tempered (harder) than air dried.

After 2 years, I would think the air dried wood, unless it's huge timbers, would be sufficiently dry.

After drying, I don't think either type would be more or less susceptible to movement.


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## stinnettjn1 (Aug 18, 2011)

He said it was cut and stacked with slats between boards. I think I'll give it a go and see how well it works out. Also, how long is long enough for air drying, given it is cut and stacked with slats between for good circulation? Thanks for the input guys.

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## jaxonquad (Jan 26, 2011)

Depends on where you are.

In my area, pine that was cut in February is @ 25% currently. According to my cheap little meter.


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## ed_h (Dec 1, 2010)

stinnettjn1 said:


> He said it was cut and stacked with slats between boards. I think I'll give it a go and see how well it works out. Also, how long is long enough for air drying, given it is cut and stacked with slats between for good circulation? Thanks for the input guys.


Done properly--bottom boards kept off the ground, 1" or so "stickers" between layers, cover to protect from rain and direct sun, in an open area with good air circulation--the rule of thumb is one year per inch of thickness. Then move the wood indoors, ideally for several months.

Tracking moisture content with a moisture meter is a good way to see when MC is stabilized.


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## Wrangler02 (Apr 15, 2011)

Brink said:


> The only thing I've heard, and I never went about proving, is that kiln dried wood is tempered (harder) than air dried.
> 
> After 2 years, I would think the air dried wood, unless it's huge timbers, would be sufficiently dry.
> 
> After drying, I don't think either type would be more or less susceptible to movement.


In addition, I was told by a guy that runs a local sawmill that temporing or as he called it, case hardening, happens when the kiln is too hot and the wood loses moisture too fast.

When the wood is ripped, internal stesses are released and the pieces can warp. Another symtom is when the kerf either opens or closes behind the saw. 

I have not yet used any of the white oak that I bought last summer and is air drying in my barn


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## Manuka Jock (Jun 27, 2011)

Dried is dried . Both methods are equally as good , in general .
One just happens to be faster than the other.

There is one difference that comes to mind tho and that is that air dried wood is best for steam bending .
Something about it having already been cooked


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## cabinetman (Jul 5, 2007)

stinnettjn1 said:


> Just wondering as a newer inexperienced woodworker, is kiln dried lumber a must when building indoor furniture? The wood types I'm most curious about are walnut, maple, oak and pine. I found a local guy selling rough cut hardwoods that are only air dried (2 yrs) but I'm afraid the wood will move to much for furniture making.


All of the lumber I use is kiln dried. I just don't have the time to wait. Kiln drying provides for a control drying process to a moisture content around 6%. If air dried, that low of a percentage will likely not be achieved, and using air dried that has some moisture to lose, can shrink/warp with more drying.

Wood will dry to a certain point relative to the ambient moisture. A percentage loss can be checked by weighing the lumber prior to storing and checking its weight periodically. Once the wood stops losing weight, it's likely as dry as its going to get. The accuracy of this testing will depend on the method of weighing. The weight loss can be figured in the percentage of moisture loss, but not an indicator of moisture content. A moisture meter is still the best form of testing.










 







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## Daren (Oct 14, 2006)

You are getting some good answers here. As was mentioned I do have a kiln, it's a big help in drying my wood that I need to use/need to sell right away (instead of waiting 2 years for it)...but I am not afraid to and do use properly air dried walnut and maple (don't have much use for pine, flat don't like oak) as well as many other species like cherry-ash-cedar, simply air dried...After it is acclimated to where it's going to be put into service. As a matter of fact the desk I am sitting here typing this is made from air dried walnut.

Where you are and how thick were brought up, both good points. If you live in Las Vegas NV air dried wood is going to be sitting at 5%-6% MC (plenty dry)...If you live in Green Bay Wis. air dried is going to be about 15%, you can't build with wood that wet and bring it inside. (10% MC tops is what I feel comfortable with) http://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf
Scroll down a few pages to find your area. The chart is not 100% correct, but close=ballpark. It has been very dry here (central Illinois) for several weeks and I know the air dried wood in my shed is under 10% at this very moment, which is a few % lower than the chart shows it should be...As was said you need a moisture meter-that will save a lot of potential headaches when dealing with air dried wood if you plan on bringing it inside as furniture.

Air dried pine could ooze sap for years, if it is a sappy species, not being kiln dried and the ''pitch set'' with high temps.

Interesting reading on even wood that has been kiln dried then stored in an out building/unconditioned (heated/cooled) space. http://www.woodworkingtalk.com/f26/storing-kiln-dried-wood-20014/


.


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## stinnettjn1 (Aug 18, 2011)

Thanks for all the great answers and for the link to the chart. I have a good idea of what to look for now. It is MUCH appreciated!

Jeremy


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## Jr.Woodchuck (Nov 9, 2010)

I have used air dried and kiln dried lumber. Air dried may, may I say, move a little more easily due to humidity changes than kiln dried. Air drying will never reach the lower MC of kiln dried. However, unless you are going to place the furniture someplace where the humidity changes from a very low to a very high and stays that way for extended periods then air dried lumber is OK for furniture. Kiln dried lumber can not be harder than air dried. Dry lumber is dry lumber. I just went through this with some quarter sawn oak. The old term is case hardened. It is not "hard" it means that the operator of the kiln did not add or did not add enough steam at the end of the schedule. This will cause a board to bind on a saw while you are cutting it. Nice way to check for stress in your lumber is;
Cross cut about 6" off of a 6" wide board.
Layout a 1" to 1 1/2" slot along the grain about 3" deep.
Cut the slot on a band saw.
Measure your slot. If it is the same on both ends no stress present.
The degree of difference tells you how much stress is in your board.

Changes due to Stress show up immediately. Changes due to humidity will take hours or even days.


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## MidGAOutdoor (Apr 7, 2011)

good information here.


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## Jig_saw (May 17, 2015)

Kiln drying gives better weatherproofing than air drying. That is why all high quality musical instruments are made from kiln dried wood. Kiln dried maple and spruce preserve tonal quality of an instrument much better than what is possible with air drying. High end violins made from kiln dried wood can maintain their tuning even in wildly varying weather.


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## Tony B (Jul 30, 2008)

Here is my understanding of how this works so someone please correct me if I am wrong. 
There are 2 types of moisture in the wood. One is free moisture and the other is bound moisture. Free moisture is the water that sits in the cells of the wood kinda like water in a tube. Then there is the bound moisture. This is the moisture/water that is actually trapped in the walls of the cells themselves.
Air drying dries up the free moisture in the cells and this works relatively quickly after the tree is cut and then tapers off to that 1" per year thing. The bound moisture, other than living in the desert, will take a very, very long time to leave the wood. In some areas it will never dry completely down to the 6 - 8% that furniture makers want. 

BTW, when I was active several years ago, Daren and Cabinetman were very active. This thread is from 2011 and I was wondering if these 2 guys still around?


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## Steve Neul (Sep 2, 2011)

Tony B said:


> Here is my understanding of how this works so someone please correct me if I am wrong.
> There are 2 types of moisture in the wood. One is free moisture and the other is bound moisture. Free moisture is the water that sits in the cells of the wood kinda like water in a tube. Then there is the bound moisture. This is the moisture/water that is actually trapped in the walls of the cells themselves.
> Air drying dries up the free moisture in the cells and this works relatively quickly after the tree is cut and then tapers off to that 1" per year thing. The bound moisture, other than living in the desert, will take a very, very long time to leave the wood. In some areas it will never dry completely down to the 6 - 8% that furniture makers want.
> 
> BTW, when I was active several years ago, Daren and Cabinetman were very active. This thread is from 2011 and I was wondering if these 2 guys still around?


I think your assessment of the drying wood is spot on. I've had antique furniture that was over 100 years old dry more from just moving it to a dryer climate. The wood just reaches a balance with the climate it's in and stops drying until moved someplace dryer. 

I don't know about Daren but Cabinetman died.


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## Tony B (Jul 30, 2008)

Thanks for the info. Sorry to hear that C-man passed on. I dont know how old C-man was but I think he was around my age - 69. 
Maybe Daren got either bored or real busy in the sawmill business. 
ScottyD (mdntrdr) dont spend much time here either. I know his business seems to have really picked up. I spoke to him by phone the other day by phone. 

I got bored/burned out with this forum a few years back. Now that I am retired and no longer have a shop, I am back on here and really enjoying it - go figya


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## woodnthings (Jan 24, 2009)

*really?*



Jig_saw said:


> Kiln drying gives better weatherproofing than air drying. That is why all high quality musical instruments are made from kiln dried wood. Kiln dried maple and spruce preserve tonal quality of an instrument much better than what is possible with air drying. High end violins made from kiln dried wood can maintain their tuning even in wildly varying weather.


I suppose Stradivarius went down to the local kiln and picked up some Spruce for his instruments.....:surprise2:
Back then there were no kilns, but these days KD is used routinely:






I don't think the back side of the face or inside of any instrument is "finished", mine aren't anyway, only the visible surfaces. The thicker the finish the less resonant the sound, so an acoustic guitar with a zillion coats of lacquer buffed out won't sound as good and the same guitar with fewer coats. My friend had his Martin D 18 "factory refinished" by Martin, to a high gloss and it came back sounding worse than when it was new. 

Only if you finish both sides of the wood will you prevent ambient moisture from changing the "tone" and no one who makes guitars does that that I'm aware of.
You always tune an instrument before playing for that reason, BUT some stay in tune better than others. When kept in a constant environment they change very little, it's when you put them in the van in very hot or cold weather and then bring them inside they'll need to be tuned.


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## TimPa (Jan 27, 2010)

here in northern pa, the lowest mc I have ever seen from (outside) air drying is about 12 %, too high for furniture projects. extra steps will have to be used to get it to 8%. so we rely solely on kd for indoor projects. it looks like location and climate will make air drying more or less considerable of an option.


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## thewalnutguy (Oct 31, 2010)

Here in central MN kiln-drying for wood to be used for indoor furniture MUST be kiln dried. The lumber that I saw gets stickered on pallet racking in an unheated building with multiple roof turbines, the lowest I've ever found after several years of storage is about 17%. I just pulled some 4/4 quarter-sawn white oak that was cut in 2010 and the moisture level was 18%. It's now in a dehumidification kiln, and will probably take about a month to come down to 8%. I've tried pushing the kiln schedule a little faster, but found the degrade level (twisting, warping, cracking) to be unacceptable and now follow the guidelines from the Ebac kiln manual. I once tried "tempering" some air-dried wood by storing it with stickers between layers indoors and even after a year it still showed close to 12% (indoor shop is heated and air conditioned).


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## woodnthings (Jan 24, 2009)

*Ebac?*



thewalnutguy said:


> Here in central MN kiln-drying for wood to be used for indoor furniture MUST be kiln dried. The lumber that I saw gets stickered on pallet racking in an unheated building with multiple roof turbines, the lowest I've ever found after several years of storage is about 17%. I just pulled some 4/4 quarter-sawn white oak that was cut in 2010 and the moisture level was 18%. It's now in a dehumidification kiln, and will probably take about a month to come down to 8%. I've tried pushing the kiln schedule a little faster, but found the degrade level (twisting, warping, cracking) to be unacceptable and now follow the guidelines from the Ebac kiln manual. I once tried "tempering" some air-dried wood by storing it with stickers between layers indoors and even after a year it still showed close to 12% (indoor shop is heated and air conditioned).



I shipped an unused EBAC to MN a few years back. Was it to you and was it posted here? Send me a PM if so. :smile3:


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## hts1965 (Jan 19, 2016)

When I was in trade school the carpentry used to buy 2 lifts of rough pine a year. each years lumber was stored in the basement below our shops and air dried on 1 or 2 year rotation. It was warm and dry because the boiler for the school was nearby and kept it about 70+ degrees. We built furniture, boats, restored many components from historic homes in the city. Shrinkage never seemed to be a problem, but we did a lot of joining smaller widths together. I had no idea what a moisture meter was in those days, but I do know one thing for sure, If we soaked a piece of air dried wood, it would dry much faster than any kiln dried wood would. KD seems to retain any added moisture much longer under identical conditions. Granted, kiln drying was just beginning then. I also know that in the 70's I built my house. For the bearing walls I used KD stock, but for non bearing I used local air dried rough 2 x 4's. after a few years every KD wall had kinks and bows in them. And yes, I did check and use the straightest studs. All of the rough air dried walls are still straight after 38 years. One wall with only one side drywalled I can put a straightedge on them and there is a kink at every knot, or spot of wild grain in the wood, unfortunately not all the same direction. I have had similar results with KD vs air dried for finish and furniture. KD definitely should be protected more after being removed from the kiln and stored. I have gone back and seen what age has done to work I did 20, 30 or 40 years ago.


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## Jig_saw (May 17, 2015)

*Are you sure?*



woodnthings said:


> I suppose Stradivarius went down to the local kiln and picked up some Spruce for his instruments.....:surprise2:
> Back then there were no kilns, but these days KD is used routinely:



Well, kilns have been around for thousands of years so how do we know that Stradivarius did not used kiln dried wood? There is still intense scientific debate on how Strad managed to produce the sound which other makers of the era could not. Maybe kiln dried was the reason.:wink2:


Currently most high end violin manufacturers used kiln dried wood.


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## TimPa (Jan 27, 2010)

I'm sure there were many other things they did to choose the perfect sound boards material. 


the moisture content in my opinion would have been relevant. we have to use wood with a mc of 6-8% so that it doesn't react when we bring it into our sealed and insulated, heated/air conditioned house, with a roof, doors, windows and not a dirt floor. when they brought their projects indoors, the ambient humidity was likely close to the same as outdoors


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## Tennessee Tim (Dec 15, 2010)

From all I've read in the South, most instrument builders wanted and used AD lumber They claim the tone was better. This may have changed in the last 10 years??? THIS also may be differ in different parts of the country (USA) or other countries around the world due to their local MC.

I'm still old school there....AD !!!!


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## Tennessee Tim (Dec 15, 2010)

So I got curious.....What is being produced for lutheirs..... how is it done.....what's changed???

So far what I've found on the "net" that made since from known premium woodtone sellers is that most use slow drying/ADing as the first step for the best wood stabilization, THEN it is KD'd for a lower moisture content for our controlled enviroments they will be used in.

So I stand half way corrected :crying2::|....they are using more KD'd lumber, BUT not straight from the saw!!!! :nerd2::nerd2:


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## woodnthings (Jan 24, 2009)

*It wasn't just about moisture content back then*

Wood density affects the sound according to this article:
https://www.sciencedaily.com/releases/2008/07/080701221447.htm 

Quote:
The average wood density of the classical and modern violins did not differ significantly. However, the differences in wood density between early and late growth were significantly lower in the ancient violins.

Since differentials in wood density impact vibrational efficacy and thereby the production of sound, it is possible that this discovery may explain the superiority of these violins. This insight offers new possibilities into replicating the tonal qualities of these ancient instruments, as the researchers conclude in PLoS ONE.


And now they can do this:

https://www.sciencedaily.com/releases/2012/09/120908081611.htm


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## Jig_saw (May 17, 2015)

Air drying, although preferred if carried out in a drier climate, has a lot of variables like temperature and humidity which are difficult to control. In tropical climates, air drying will always leave a higher moisture content, and if the product is shipped overseas to be used in temperate regions there will be further drying leading to shrinkage. The opposite happens if the air drying is done in a temperate climate and the instrument is to be used in the tropics.

In contrast, kiln drying by modern methods allows a precise control over temperature and humidity leading to better results independent of geographical location. Plus it is much faster!


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