Official Luthiers Forum!

I've been working with torrefied/thermally treated lumber quite a bit recently at work mostly for things such as decking and outdoor furniture, but some people have used poplar as a substitute for walnut. It is mostly being pushed as a green alternative to pressure treating and it has some interesting properties including better dimensional stability and rigidity. What I've noticed is that it's remarkably resonant, probably from the ridiculously low moisture content. Has anyone used thermally treated wood in a guitar build? If so, how did it work out, sound, play, etc.?

I'm tempted to try building a neck for one of my bolt-ons from torrefied maple, since it should be completely safe to leave the back bare and it acoustically rings like a bell... Unless there are horror stories already from it being potentially too brittle.

I recently made a strat neck from what was called "cooked maple", I'm assuming that's what you're talking about?
Smelled horrible.
Sounds and feels great.
seems extremely stable through temperature and humidity changes.
It did loosen up some eyes in the birdseye maple that it started out as which required gluing. I don't think they were loose, but seemed easier to tear out with my wood rasp.

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Old growth, shmold growth!

I bake all spruce tops for 2 hours @ 200*F in a home made oven. I use a bending blanket as the heat source.




The tops are definitely more musical when they are dry.

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JJ
Napa, CA
http://www.DonohueGuitars.com

I'm noticing quite a gap there between the last screw hole on the bottom and the one to its left, JJ.
Anyone else notice this too? I would have thought he would have laid them out more carefully...

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

And that, my fellow OLFers, is why "The Don" was institutionalized during his recent sabbatical years! Welcome back, Don!

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JJ
Napa, CA
http://www.DonohueGuitars.com

Yes JJ, and it was nice of you to visit me there for all those months...

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

TGW: that's the stuff! I'll upload a picture of the box of thermally treated poplar in my office tomorrow. It's dark brown and smells like a smokehouse. The treatment process takes the temperature as high as possible without setting the wood on fire. It has potential as an exciting material for guitar building... At least I'm excited.

Not the greatist pic, but the guitar sounds great with this well cooked maple neck.
The wood is very brittle, lighter than "raw" rock maple and sucks up finish like a sponge. There is no tint or stain on the wood, dry it cold pass for Walnut, but got it wet and it matched the Cocobolo pickguard very well.

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How long is that in luthyears?

What are the details of your roasting protocol?

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JJ
Napa, CA
http://www.DonohueGuitars.com

My understanding is that the process takes the lumber to 400°F+ in an anoxic environment, typically nitrogen, to prevent combustion for several hours. These conditions drive out virtually all moisture and sugars as well as the most volatile organics. Supposedly this renders them capable of withstanding the elements at least as well as pressure treated lumber. From everything I've gathered about the effect of aging on acoustical performance it is remarkably similar to thermal treatment. With less water, sugars, and organics, the wood takes on a much different strength to weight ratio and allows it to more effectively ring. I have a submersion test running at work to see how little it actually absorbs, because it's not completely hydrophobic as the manufacturers claim it to be. It glues up beautifully, and seems to machine very well. I'll cut some dovetails by hand to see how it handles sometime this week. I do not expect it to work well for backs and sides, but for solidbodies, necks, and tops it holds some real promise.

If you want some more information, try googling thermally treated lumber and torrefied lumber.

http://newbiomass.com/torrefied-wood/
Looks to me like torrefied wood would be completely black and extremely brittle.
What we use for necks and tops most likely falls somewhere in the middle or closer to the beginning of the process, otherwise I don't think we could make guitars out of them.

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Old growth, shmold growth!

Here's the poplar I have in my office. Time to get some of this stuff glued up so I can test its' strength in the Instron next week.

Where are you guys sourcing this stuff? Any links you can post?

There aren't many producers of thermally treated lumber in this country yet, I know of one in my state which is Keim Lumber in Charm, OH.

I have some interesting results from testing as well. Volumetric testing is a water soak and it tells us quite a bit about its' dimensional stability. Currently, we have samples of Ash and Poplar. After 42 days here are the results:

Untreated Ash: MC=81.3% DVolume=14.5%
Treated Ash: MC=66.4% DVolume=4.6%
Untreated Poplar: MC=109.6% DVolume=14.9%
Treated Poplar: MC=94.5% DVolume=8.3%

Starting MC of the treated lumber is around 3-3.5%, and as you can see the manufacturers aren't kidding about moisture having minial effect on dimensional stability.

I also ran a 4-point flexural loading test on one of our Instrons to determine flexural modulus. My anticipation was that the modulus might be somewhat elevated. These tests were far from exhaustive, and the most interesting result was observation of brittle failure (I'll post some pictures soon, it looks wild for wood.) All numbers are reported at 99% confidence interval.

Treated Ash: 529.4 ± 7.6 ksi
Untreated Ash: 1076.0 ± 3.2 ksi
Treated Poplar: 952.8 ± 10.8 ksi
Untreated Poplar: 824.2 ± 4.6 ksi

D-905 results were excellent on treated poplar showing 100% wood failure on all specimens and average strength of 1347.7±188.6 PSI reported at 90% confidence interval. Which is therefore a representation only of the shear strength of treated poplar.

Thus far I am not deterred, and think I'll see if I can get some treated maple to test and also build a bolt on neck with to see how it works for myself.