Air Drying vs Kiln Drying Tonewoods

[BlindBo]

A friend has a log of Chinese Pistache he cut from his property and would like to cut it up into back and side sets. He has a guy who will 1/4 saw it for him. He is planning to kiln dry it and has asked me about it. I have no experience with sawing or drying wood for guitars but told him I’d see what I could learn. From reading, it appears most traditional builders prefer air drying. I have not gotten any responses about using kiln drying other than one thread I found here that mentions solar kiln use.
My friend doesn’t really want to wait several years for air drying if possible. Is there anyone here who uses kiln drying on green wood? If so, I’d appreciate any comments you can give me.
Thanks

[Diane Kauffmds]

I don't know much about it either, but kiln drying sounds a lot like torrification. Torrification is a way of speeding up wood aging. It changes the tone and the way wood has to be handled when building with it.

People have their own opinions on sound; some people love torrified wood; others don't. Personally, I prefer to work with and play natural wood. IMO, there's no shortcut or substitute for natural age.

He could torrify a set or two, and air dry the rest.

[Bob Gleason]

Torrification is a lot more radical than kiln drying.I resaw a lot of wood for people and have done and seen quite a bit of kiln dried wood. Kiln drying correctly is a very exacting process. Very easy to make nice wood into twisted, cracked , or case hardened wood. If the wood will be commercially kiln dried, then the chances of it being done well are better, not sure fire though. You can't just stick instrument wood in a kiln with a bunch of different species and expect good things to happen. Air drying is slow , but a
lot safer. I think most of us that work with raw wood, air dry our wet wood for a long time. In any damp climate, you will be forced to dry it further and to a moisture level lower than than the ambient rh. Generally people use dehumifiers and a good moisture meter for that,so it sort of gets kiln dried at the end. Wood that has been at least partially air dried to at least under 20% or less is almost always easier to resaw than kiln dried wood. The generally acceptted moisture content for use in lutherie is 6-8%, but there are caveats for understanding what that means. If your friend wants o learn about this stuff, he should read Understanding Wood by Bruce Hoadley.Many consider it the wood bible.

[tippie53]

as Bob point's out wood drying is a process.

I worked around sawmills for a lot of years. My friends mill had do both air and kiln drying
with this , you will see just how wet the wood actually is when first cut.
I am not familiar with this particular specie of wood but my best advice is
get some stickers to place between the slabs. I would also suggest using some web tie down for clamps or at least some weights.
The stickers should be at least 3/4 in thick for air flow. The first few says is very important as you don't want to dry it too fast, so avoid direct sun or al least lay something to shade the wood for a few days. they figure about 1 year per inch.
I used to air dry a lot of pine and after a few months I would move the wood to my rafters in my shop where it got HOT and used a fan to move air. best of luck and post pics
Bob if you can add anything please do I respect your wood knowledge

[BlindBo]

Thanks Bob and John, this is good information. I sent him a copy of your responses. Is there a kiln drying method that is safer and produces good results? He’s now thinking of trying kiln drying on a portion of the wood and air drying the rest. I haven’t seen the log yet, so, I don’t really know how much he will get out of it. My sense is that he’s anxious to get things moving.

[tippie53]

kiln drying is a weeks long process and not a few hours
when we did kiln drying at the mill we started with air fans for the first 72 hrs or till we got the wood from the 25%/30% green to about 15% then we started de humidification , this was with some serious dehumidifiers where we could bring the RH down about 5% at a time. Once we were at about 12% moisture on the wood we would turn on the heat starting at about 85 degree and work up to 100 and as the heat went up we lowered the RH . the lowest the dehumidifiers would work was to about 35% and then we would monitor the wood moisture till we saw 8%
then the heat went to 110 and once we were under 8% and over 6 we just set the dehumidifiers to 45% and temp to 80 and let the fans blow for 72 hr. This whole process usually took 28 to 30 days. You can't dry too fast you will split things
we did more commercial drying as most of the wood went to furniture and casket companies. Never had a complaint from the casket customers

[BlindBo]

Bob and John,
My friend had is saw mill guy call me today wanting to know how thick he should make the quarter sawn planks for drying. I told him I had read a minimum of 1”+ kerf. Since I’ve never been involved with this, I thought it would be good to get y’all’s guidance. I told him after drying, the planks would be resawed into two nominally 1/2” planks which would then be resawed again to yield 2 book matched sets of 3/16” thick boards. He said he might need to add a little extra to allow for any warping.
What thickness planks should he start with for drying?
I’m learning that like most things in luthiering, this is not as simple as it initially appeared!😂
Thanks for the help.
Bo

[Bob Gleason]

I don't know how big this log is, but sawing it green to 1" thick planks is probably going to be a disaster. Unless the drying is picture perfect, and things dry dead straight, you'll likely only get 3 pieces out of that 1" lumber when you resaw it later, but probably not 4. For the purposes of later resawing into instrument wood, around here we rough saw on the mill at about 2 1/4" or 2 3/8" if there is room. That should give you at least 3 bookmatched sets and 4 if your resaw setup is really good. There are some pretty wild claims out there about resawing, but not all are to be believed. If your friend is not well acquainted with instrument wood, I would tell him just to saw it into nice lumber. People think instrument grade wood is like gold, but unless it is processed well, it's just fools gold!

[BlindBo]

Thanks, Bob. That is probably good advice. His saw mill guy is well respected locally but has no experience with instrument wood. When I described the resawing to 3/16” boards, he said his band saw would need some improvements to do that. I’m coming to the conclusion that we are all probably in over our heads.
I further learned last night that this isn’t a trunk log, it’s a 20” diameter branch, not sure how long. John was saying that branch wood is not likely suitable or large enough.
If you have any other thoughts, I’d appreciate hearing them.
Thanks so much,
Bo

[Skarsaune]

Branch wood that's 20" diameter can yield guitar-sized planks. The problem I've had when sawing/milling branch wood is the tension built into the wood from growing sideways instead of straight up and down. It leads to "reaction wood", where the plank springs immediately when it's cut from the cant.

If you think about the loads on a horizontal beam, ie the branch, the upper half is in tension, and the lower half is in compression. The planks will pretzel up when they are sawn. You can sticker them and put a bunch of weight on it to try and straighten them out but it's not a guaranteed proposition.

I've air dried and solar kiln dried wood we've milled. The solar kiln is a 'gentler' process than regular kiln drying. I will load our kiln this spring and let it run all summer. It's not super fast but it's quicker than waiting a year per inch. I'm lucky in that I've sawn wood for 5 or 6 years, so by the time I get around to using something, it has usually been through the kiln plus air drying in the barn.

I tend to mill logs at 1.5 or 1.75" nowadays unless I know I need some other dimension. I only pick out the special stuff for guitars.

Here's some walnut backs I re-sawed this winter. These two boxes are closed waiting on binding now. This is from a log we milled probably 5 years ago.

walnut.jpg