Kiln dried vs air dried

[Trkdriver99]

I have a question for all you good musket builders.  I hear that all stock blanks should be air dried, not kiln dried.  What is the reasoning behind this other than that is the way it was done way back when.  I have heard that you can let a piece of kiln dried lay around for a while, a year or so, and it will work then. I have a nice piece of curly sugar maple that was dried in a kiln, is it OK to use? It has been in my basement for about 18 months and in a wood shop for a while before that.  I also have a piece of walnut that was cut 15 years ago and has been in a barn since. I think the maple is prettier.

Ronnie

[Acer Saccharum]

I don't build muskets, nor am I good, but I use air dried, because that's what I have.

I have heard that the kiln dry process drives out more moisture than air drying ever will, like chemically bonded water, and will not reabsorb that water. I may have made that up.

Wood shrinks more along the growth rings (circumferentially) than it does from edge of the tree to the center (Radially).  So if you use quarter sawn wood the shrinkage will not show as much at the toe of the buttplate, as it would if you use plank sawn.

That's all I know, and I'm sticking to my story.

Acer

[Stophel]

I think that some people just have this idea that kiln dried wood is just awful and totally unuseable.  Where that comes from, I don't know.

If it weren't for kiln dried wood, I imagine a great number of guns, modern and muzzleloading, could never get made since there just ain't enough "air dried" wood available.

[Acer Saccharum]

Just go get a tree, saw it up, and stack it. You'll have plenty of air dried wood, Stoph.

[Paddlefoot]

My understanding of the kiln vs air dried issue is that if the wood is kiln dried from the beginning it presents more of a risk of having problems with checking and unknown internal stress. It may tend to move more as it is cut and shaped. Just what I heard around the old pot bellied stove at "The Flintlock".

[close enough]

I have used both for furniture making.  I wouldn't worry about using either one.
Brian

[Randall Steffy]

I work with kiln dried wood everyday and was watching with anticipation to hear what others offer as opinions of air vs. kiln drying. My experience is that kiln dried is a much more stabilized wood with the "backbone in check" to some degree. Air dried wood is more "wild and free spirited" with the life still in it. There is little down side to properly kiln dried lumber, however too rapid or too hot a kiln does seem to harm or weaken the wood's fiber and strength. I see air dried wood as far more affected by humidity and prone to more extensive warping from internal stresses, never fully settled down. Again, kiln drying seems to lessen the tendency of the stock to move at every opportunity. Personally I would choose properly kiln dried wood, but use well seasoned air dried if that is what I had on hand.

[Acer Saccharum]

Randall, my experience with air dried is that the wood will often contain internal stresses that show up when you saw a slab off the forestock, for example. The stock can take a real bender. I like to air dry my planks for several years, then saw them into rough blank shapes, and let them dry for some years more. This alleviates the problem, but it's no guarantee.

Acer

[George F.]

I really love the wood that Freddie Harrison has. I stopped  over Freddie"s on my way down to Florida this past May to buy "a few stocks"  He has a few old semi-trailers boxes on the ground loaded with stocks. The ones that are still drying are heated with a flood lamp, a couple per trailer. They're all sealed on the ends. But talk about a kid in a candy store. I had to call my bank to get special permission to withdraw more that my daily limit, and they would only  do it once. Good thing! ...Geo.

[Paddlefoot]

Wow. So many of you have experience that was exactly the opposite of what I have always been told I do wonder if a lot of my long held beliefs are just based on old wives tales or what. I need to be working more wood.

[Bioprof]

I think I heard something one time that kiln dried walnut will lose some of its color and that it sometimes has to be steamed to get the nice color to return.   

[Long John]

In a modern hardwood lumber kiln rough cut green stock aat a nominal 20 percent moisture content is placed in the kiln and the temperature is rapidly ramped up to approximately 220 F and 100% relative humidity.  This causes the humidity (moisture content) in the lumber to be at the same level as the air outside.  This temperature is maintained as the humidity is slowly reduced by circulating a fraction of the air out of the kiln, dehumidifying it and then returning it to the kiln interior.  As the humidity is taken out of the air the moisture in the lumber flows out of the wood.  Over time the moisture content of the wood and air is brought down until the moisture content of the lumber is a nominal 7%, dry basis.  Since the moisture content is maintained at a uniform level throughout the lumber the entire stick shrinks at the same rate, minimizing checking.

Air dried lumber starts at the same 20% moisture content but the moisture leaves the stick at the surface first.  If the moisture loss at the surface is too fast the surface wood shrinks while the core wood is still fat, causing checks. As the moisture leaves the surface of the stick mositure from the center slowly migrates to the surface.  The key to air drying the stick is slow reduction in moisture content.  Air dried lumber will achieve a nominal 10% moisture, dry basis.  I generally figure about 1 year for each inch of plank thickness.   However, air dried lumber rarely gets below 10% moisture content, dry basis.

With air drying you don't have temperature working for you to drive moisture out of the stick.  Consequently, it is more likely that there will be regions in the stick that did not achieve the same dryness as others.  When you cut such a stick the drying process will continue once the not-so-dry wood is exposed, leading to warps and twists 1/2 way through a project.  This can be minimized by taking your thoroughly air dried lumber stock and putting it in the attic in the spring for storage over the summer.  The heat in the attic space will help drive reluctant moisture out of the lumber core.

Air dried lumber is slightly more flexible and shock resistant.  Kiln dried stock is more dimensionally stable. Take your pick.

Best Regards,

John Cholin

[Daryl]

I've read most of the posts, scanned others.
: My take on kiln vs air drying is that air drying takes years, while kiln is done in a day or so.  The moisture is driven out faster with the kiln, of course, and in some applications, this is good, others OK and others not so good. For stock wood I don't think it matters. For making self-bows, air drying is better as the cell structure of the wood is not harmed, but arriving at the 'perfect' moisture content is more difficult.  I've made some spectacular bows from both air and kiln dryed wood - go figure! 

[wmrike]

About fifteen years ago I slabbed some walnut.  Being bored at the time, I suppose, I weighed each piece and wrote the weight and date on the slabs.  This was repeated every couple weeks.  Within about three months the wood was at a weight that has not changed since.  I have no way to quantify moisture content other than bulk weight, but three months to stable seems pretty fast too me.  Well, $#*!, the wood has been sitting around for fifteen years, so what's the rush?

Having watched this and other wood air dry over the years, I rather suspect that the posters above who ascribe more rapid stabilization to the kiln-dried stuff might have it right.

[Dphariss]

The wood must be old enough, out of the tree long enough, to be stable. You can dry a piece of wood to 7% and still have it do undesirable things when made into a stock. Let it normalize for a few years and it will be far more stable when shaped into a stock.
Dry and stable (for precision work) do not necessarily go together.
Wood that is stable will still get larger and smaller depending on where it is. But nasty changes in dimension and/or gaps in the inletting are not going to be nearly as pronounced as in a piece of wood kiln dried then made into a stock shortly there after.
One of the reasons air dried is better most of the time is that its older and more stable.
Dan

[T*O*F]

Considering that all wood was once air dryed and has held up for 200-300 years with no problems other than a bit of shrinkage, why even ask.  You see very few guns that are wop-jawed from twisting and the inletting is still tight and gapless.

I think most of the problems occur because trees ain't as big as they were then.  In the quest to maximize profits, you get a lot of slab sawn blanks being sold and they are the ones that do all the twisty warpy stuff.

Another method you don't hear about today is the water drying of wood.  Lumber was sawn and sunk in a pond or lake to stabilize.  Drying gets rid of intra-cellular moisture.  As that moisture is displaced, the wood shrinks and stabilizes.  Thereafter if it gets wet, it is inter-cellular moisture.  When wood is stabilized under water, the intra-cellular moisture leaves the cell walls thru osmosis, resulting in wood which is just soaked and can be air dryed in a very short time.

I have seen at least one reference that said the best stockwood could be obtained by walking along a river and searching for walnut snags which had been growing on the river bank.  The river bank eroded away during flood season and the tree fell into the water, where it remained submerged while it stablized.

Similar wood have been found in such areas as Lake Superior, where old growth trees were logged out and floated down a river to the lake.  Many of these logs remained under water for decades and today command a super-premium price.  There is a whole cottage industry that recovers and sells these logs.

[volatpluvia]

I have made several guns out of wood that did not air dry nearly long enough to claim stability.  These were from trees that I helped cut up myself, so I know how old they were.   One cherry tree I made a gun of within six months.  Made one of it six months later.  Made one of it several years later.  None of these stocks ever had a single problem with warping or checking.
The last gun I made, the matchlock was cut in January 2007.  The stump, from which I took the stock stood till late in February and got soaked in torrential rains for several weeks just prior to cutting planks from it.  The slabs were so heavy I could hardly carry them.  I put them in an unheated garage.  several weeks after that I cut stock blanks out of them.  It cut wet.  During the summer last year it cracked several places.  In June this year, when I started inletting the barrel the cracks had disappeared for the most part.  I have not had any trouble with this stock.  Nor have I had any problem with the other gun I started to make from the other blank.  Just my to cents.
volatpluvia

[woodsrunner]

Neither am I a rifle builder nor even a woodworker even though I've spent a career in the timber business. This I do know, however!

The high end cabinet makers like James Kranov will not use kiln dried wood for any thing they make. Kranov says that to kiln dry wood is to kill it of all character in the refinishing and working  process.

And I do know from hanging around with hardwood lumber fellows that kiln drying hardwoods is an art AND a science. Pine is easy to properly kiln dry. Hardwoods are very difficult.

[Stophel]

I have made several guns out of wood that did not air dry nearly long enough to claim stability.  These were from trees that I helped cut up myself, so I know how old they were.   One cherry tree I made a gun of within six months.  Made one of it six months later.  Made one of it several years later.  None of these stocks ever had a single problem with warping or checking.
The last gun I made, the matchlock was cut in January 2007.  The stump, from which I took the stock stood till late in February and got soaked in torrential rains for several weeks just prior to cutting planks from it.  The slabs were so heavy I could hardly carry them.  I put them in an unheated garage.  several weeks after that I cut stock blanks out of them.  It cut wet.  During the summer last year it cracked several places.  In June this year, when I started inletting the barrel the cracks had disappeared for the most part.  I have not had any trouble with this stock.  Nor have I had any problem with the other gun I started to make from the other blank.  Just my to cents.
volatpluvia

You may have lucked out in that it was cherry, which is widely regarded as being one of our most stable woods.  You may or may not have such luck with other types of wood.

[keweenaw]

If you guys think that most of those quite wonderful stock blanks we buy are all air dried, you're dreaming as most commercial wood suppliers can't keep their capital tied up in inventory for the time it would take to air dry the wood.  Most of the eastern US where the curly maple comes from is pretty humid country.  Drying a 12/4 plank down to dryness takes about 3 years.  If you cut a blank out of it wet it will obviously dry faster as the surface area is less but it's also much more inclined to warp.  Most maple drying is done by stickering and stacking the wood for 6 months or so to get rid of the bulk of the water, after that it goes into the kiln.  Kiln schedules are radically different for 4/4, 8/4, and 12/4 wood so they can't be done in a mixed load.  The 12/4 stuff takes more than 3 times as long as 4/4 so most kilns operators won't do 12/4 stuff at all. 

A fair number of the savvy operators are no longer using heat kilns for specialty woods like 12/4 maple.  They're using vacuum kilns where the water is drawn off without increasing the temperature much if any.  The kiln operating costs are much lower and according to most produces a superior product.

An interesting experiment would be to take planks from one tree, air dry some and kiln dry some to the same moisture content and give them to a great builder to see if he could tell the difference. 

Tom

[T*O*F]

An interesting experiment would be to

make up a large baggie with a fitting on it that could be hooked up to an AC vacuum pump and draw the bag down to a vacuum.  Kinda like a big Seal-A-Meal.  It could probably even be done with an old vacuum cleaner motor.

I was always gonna try it but never got around to it.  With today's sheet plastics and adhesives, it's certainly not that hard to make an airtight bag.

The vacuum removes moisture because water boils at room temperature when under a vacuum.  The water turns to cold steam and gets sucked out of the pump outlet.

[Long John]

Daryl,

The kiln operators for whom I have worked quoted kiln schedules between two and five weeks, depending upon species, thickness and moisture content coming in.

All of the kiln operators for whom I have worked fuel the kiln by burning scrap wood from the other end of the plant.  Most of the lumber kilns I have seen stand about 30 feet high by 40 feet wide and perhaps 100 feet long.  They are loaded with diesel forklift trucks that carry hacks of a ton or more.  I can't imagine trying to make a vacuum chamber that large.

Best Regards,

John Cholin

[northmn]

I was told not to get a camera for pictures as one is a coming. I find this thread interesting because I would mention to people a quick way to dry wood as published in the Traditional Bowyer books.  Every time a couple of people would jump and say I didn't know what I was talking about and horrible things would happen using that method. They just got an F in Industrail Arts.  I just built a fowler in which I dried the stock in 4 months.  It worked.  One of the things about any differences between kiln dried and air dried is the degree of heat applied and the speed of drying.  Wood cells can be damaged by too much too fast.  Some of the wooden tool handles were good examples as they broke easier.  Kiln drying of good grade lumber has been refined over the years.  Track of the Wolf advertises stocks dried down to 7% as being more stable.  Unfortunately wood will regain ambient moisture.  If your climate is humid as in Northern MN, the stock will absorb moisture as you build on it.  When I built my fowler, I returned it to the hot box a couple of times due to this, as the lock mortise would swell as would other inletting areas.  Older wooden furniture commonly swells and contracts such that glue joints pop in my neck of the woods.  An instructor in IA I had mentioned that hardwood floors are great in Colorado with an annual rainfall of 12" but not so good in MN with over 48 inches. Air drying will not get the wood as dry as kiln drying, and has no real advantage over properly kiln dried wood, or any wood that has had the drying process speeded up.

DP

[Dphariss]

I have made several guns out of wood that did not air dry nearly long enough to claim stability.  These were from trees that I helped cut up myself, so I know how old they were.   One cherry tree I made a gun of within six months.  Made one of it six months later.  Made one of it several years later.  None of these stocks ever had a single problem with warping or checking.
The last gun I made, the matchlock was cut in January 2007.  The stump, from which I took the stock stood till late in February and got soaked in torrential rains for several weeks just prior to cutting planks from it.  The slabs were so heavy I could hardly carry them.  I put them in an unheated garage.  several weeks after that I cut stock blanks out of them.  It cut wet.  During the summer last year it cracked several places.  In June this year, when I started inletting the barrel the cracks had disappeared for the most part.  I have not had any trouble with this stock.  Nor have I had any problem with the other gun I started to make from the other blank.  Just my to cents.
volatpluvia

You may have lucked out in that it was cherry, which is widely regarded as being one of our most stable woods.  You may or may not have such luck with other types of wood.

I would call it more like divine intervention than luck.
I have a very hard time believing there is no loss of dimension or fit anywhere.
I don't know any experienced stock maker who would even consider using wood this green.
Dan

[Dphariss]

Neither am I a rifle builder nor even a woodworker even though I've spent a career in the timber business. This I do know, however!

The high end cabinet makers like James Kranov will not use kiln dried wood for any thing they make. Kranov says that to kiln dry wood is to kill it of all character in the refinishing and working  process.

And I do know from hanging around with hardwood lumber fellows that kiln drying hardwoods is an art AND a science. Pine is easy to properly kiln dry. Hardwoods are very difficult.

I understand that walnut it trickier to dry (lifeless wood with poor color etc if done wrong) than maple but thats about all I know.

*Personally* I would rather have an old air dried blank. But beggars cannot be choosers.

Dan