Thermalized wood.

[Dave Bagwill]

Looking at the build process on Jan Tulacek's site I noticed the attached pic referring to 'thermalized wood' and asked Jan about it. It is NOT baked wood, something different. He replied:

I don't know the process or the technology exactly but it's basically
"baking" the wood like in a big pressure cooker I imagine, not just dry
heat. I buy this wood from a tonewood supplier Koelbl in Austria. The
result is close to the very old spruce as I know it from original 19th
century instruments. It is noticeably lighter but also more fragile
crossgrain. You cannot bend it across the grain as much as you do it
normally with spruce when judging stiffness for example. It is also non
translucent as normal spruce is. But all these qualities does have aged
spruce too. Except this wood smells a bit burned. The advantage is that
it moves much less with humidity changes. I build just a few instruments
with this wood to say anything about the sound but they all played nice
so it's not an inferior material definitely. It certainly looks good.


Has anyone else here worked with the stuff?

[ken cierp]

Yep --- Taylor for one bakes all their sound-boards (300 or so degrees for an hour). Logic/claim is that the resin is crystalized, I suppose to simulate aging?

I tried it in the kitchen oven and had problems with the stickers staining,general inconsistant color change and also a little charring even though the temp was only about 250. I have an idea for a bulb heated unit but that is on the "way back" -- back burner.

[Dave Bagwill]

This stuff is baked under pressure and is not dry baking. Probably the same effect?

[ken cierp]

Sounds similar to process used by some flooring and decking suppliers where the wood is put in an "autoclave" which is in effect a giant pressure cooker -- we used them at Johnson Rubber to treat some natural rubber parts.

[Dave Bagwill]

I think you nailed it with the 'autoclave' - here's a description from a website. Also, my student Eric says that thermalized wood flooring is making an impact in the U.s.

"resistant enough to be used, unprotected, in facades or in kitchen tables, where wetting is expected.

There are 3 similar European heat treatments: Retiwood, developed in France, Thermowood, developed in Finland by VTT, and Platowood developed in The Netherlands. These processes autoclave the treated wood, subjecting it to pressure and heat, along with nitrogen or water vapour to control drying in a staged treatment process ranging from 24 to 48 hours at temperatures of 180 to 230 °C depending on timber species. "

http://en.wikipedia.org/wiki/Wood_prese ... treatments

Also, this from Seasonwood.com: " subjecting wood to heat modification using steam and high temperatures, SeasonWood exhibits improved dimensional stability, longer durability, and a darker post-processed wood that imitates the color of more expensive exotic species. This heat-modification technology has been widely used in Europe with many wood species to beautify home sidings, wooden fences, doors, windows, and exterior decking.

Thermally modified wood has a lower equilibrium moisture content (EMC), with better dimensional stability. This means wood will shrink and swell less, ultimately leading to parts such as doors and doors frames that fit better particularly during season changes and wood shrinks and swells. SeasonWood softwoods shrink and swell about 50 percent less so. When thermally modifying lumber to higher temperatures such as 210°C (Thermo-D), moisture in the atmosphere has little negative effect on final products made using SeasonWood." And: "Specialty Products– Many other hardwood products have their performance enhanced by SeasonWood thermal modification. Examples include carvings, gun stocks and fine musical instruments. These are all enhanced by a color change and the improved stability of the wood for a longer lifecycle. Currently there are studies being carried with a musical instrument manufacturer in California to research the opportunity of thermal modification in fine crafted guitars"

[Kevin in California]

I saw some "baked" maple and oak at the wood store the last time I was there. It was a pretty dark brown, not black like charcoal, and it looked, well....burnt.
It was interesting for sure.

Kevin