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Torrefied Tonewood


Berl Mendenhall
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16 hours ago, Michael Darnton said:

Landola Guitars have been making Thermowood acoustic guitars for 20+ years.

Yes, I think they were among the first to do this kind of treatment on a bigger scale. This is my favorite guitar with heat-treated birch/spruce , I bought from a friend  that worked  at Landola, some 15 years ago.         

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  • 2 years later...
5 hours ago, carl1961 said:

How to make thermally aged tonewood on a budget, page 26 in the pdf

https://ruokangas.com/wp-content/uploads/2020/07/Thermally-Aged-Tonewood-2020.pdf

 

Nice article... interesting to see the history of wood processing.  

My major criticism is that absolutely nothing is said about DAMPING... which is the parameter most affected and IMO one of the most important.  Speed of sound gains shown are only around 3%... not a huge deal.  My processing averages about twice that... but still not a big deal compared to the change in damping.

The DIY processing box-on-a-budget is questionable as to the results, as none are given.  I haven't experimented much with non-pressurized chambers, but I don't think you can get the same results as with a pressurized chamber.  Mine was much cheaper than their "budget" version, as I scrounged equipment from eBay and made the controller and many other things myself.  It would be really expensive if I had to pay myself minimum wage.

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3 hours ago, Don Noon said:

The DIY processing box-on-a-budget is questionable as to the results, as none are given.  I haven't experimented much with non-pressurized chambers, but I don't think you can get the same results as with a pressurized chamber. 

I have never seen anything torrified at 160c,

doesn't that temp just toast it a bit and add color,

no real significant permanent structural changes.

Many hours at that temp maybe something will happen, but not an hour,,

Am I wrong?

 

What do you pressurize the chamber with?

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The article recommends many hours of cook time for the DIY 160C oven.  I too use the cooler (<180C) temperature and longer time, but with pressurized steam.  Not recommended for DIY, except for suicidal nuts.

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8 hours ago, Don Noon said:

Nice article... interesting to see the history of wood processing.  

My major criticism is that absolutely nothing is said about DAMPING... which is the parameter most affected and IMO one of the most important.  Speed of sound gains shown are only around 3%... not a huge deal.  My processing averages about twice that... but still not a big deal compared to the change in damping.

The DIY processing box-on-a-budget is questionable as to the results, as none are given.  I haven't experimented much with non-pressurized chambers, but I don't think you can get the same results as with a pressurized chamber.  Mine was much cheaper than their "budget" version, as I scrounged equipment from eBay and made the controller and many other things myself.  It would be really expensive if I had to pay myself minimum wage.

As Always Thanks for your valuable information, I had to look up damping and you also explained that well to. https://maestronet.com/forum/index.php?/topic/332772-question-about-softwoods-absorbingdamping-sound/&do=findComment&comment=682243

Now we just need you to do and sell a book!

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5 hours ago, Don Noon said:

The article recommends many hours of cook time for the DIY 160C oven.  I too use the cooler (<180C) temperature and longer time, but with pressurized steam.  Not recommended for DIY, except for suicidal nuts.

Are you using some professional pressure cooker? 170C steam is at about 9 BAR pressure, that is not that much, many common pressure chambers for steam bending wood can handle that. Of course DIY units made of PVC pipes or such can explode and cook someone alive.

I've done some "baking" of wood but without steam in oxygen free environment. I did measure density only.

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2 hours ago, HoGo said:

Are you using some professional pressure cooker? 170C steam is at about 9 BAR pressure, that is not that much, many common pressure chambers for steam bending wood can handle that. Of course DIY units made of PVC pipes or such can explode and cook someone alive.

I've done some "baking" of wood but without steam in oxygen free environment. I did measure density only.

Don has posted a picture before, I could not find it here, must be some other thread.

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1 hour ago, Loco Luthier said:

So, I can't just vacuum seal a top with my foodsaver and bake it?

I don't think a vacuum sealer will pull down enough to get all the oxygen out. it takes a good pump to do that, like the use for refrigeration. 

but not bad according to the reviews on this video

How much Vacuum does a food saver pull

 

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1 hour ago, Loco Luthier said:

So, I can't just vacuum seal a top with my foodsaver and bake it?

About 10% of the weight of the wood is bound water, which will turn to steam when you bake.  KABOOM.

I use an industrial chamber rated for the temperatures and pressures I use, but seals for high temperature are in issue.

9 bar (~100 psi) of 170C steam is pretty dangerous if a seal fails, as happened in my early testing.  I would have been badly scalded if I was anywhere near it.

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Has anybody tried vacuum freeze drying wood?

Water expands about 9% when it freezes.  So if you first soaked your wood in water and then froze it and then pulled a vacuum to sublime the ice into vapor without melting it the wood's density might decrease.

I anticipate that the wood's other properties such as elastic modulus, speed of sound, damping,  strength etc. will either stay the same, increase or decrease.

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11 minutes ago, Marty Kasprzyk said:

Has anybody tried vacuum freeze drying wood?

I don't know how well vacuum can extract frozen bound water... or what state the bound water goes into in sub-freezing temperatures.

In any case, even if you DID manage to extract the water by freeze drying, all of the water would be adsorbed back from the air later if you haven't modified the wood chemistry.  Heating to 105 C or so would be faster and easier, with the same pointless result.

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22 hours ago, carl1961 said:

I don't think a vacuum sealer will pull down enough to get all the oxygen out. it takes a good pump to do that, like the use for refrigeration.

In my experiments I followed information I collected from various papers. Basicly I baked for an hour or so at 100+C to get rid of most water then immediately packed the wood into thick aluminum foil with as little air trapped as possible (of course there is some air/oxygen in te wood but it didn't affect the results - the goal is not to burn the wood) I packed it well and sealed with aluminum tape (heat resistant). Then I baked it at 160-170C for few hours (first samples for 4 hours, the real wood for a few more) and let it cool slowly for a day or so. Then opened the packing and let the wood sit for few days. I weighed the wood to find out when it reaches equilibrium. Without the aluminum foil the wood would burn or at least darken to dark brown color. There was no problem with steam coming from wood so no need for vacuum.

But this is different from "wet" process as te water surely causes some hydrolysis and other changes in wood that the dry process does not.

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5 hours ago, carl1961 said:

@Don Noon , you might like this...

That looks a lot more complicated than just getting a PID controller and relay, which is what I have.  I don't need any fancy schedules, so it works fine for anything I want to do, including controlling varnish cooking.  Cheap and easy.

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6 hours ago, Don Noon said:

That looks a lot more complicated than just getting a PID controller and relay, which is what I have.  I don't need any fancy schedules, so it works fine for anything I want to do, including controlling varnish cooking.  Cheap and easy.

That's what I did, back when this thread was started and other threads or post from here. never got anywhere yet other than small tests. I was also thinking your way is more safe too. I tried with a home made tank and scrapped that idea fast, leaked, too much. and as for steam, I never got far, tried a pressure cooker but most steam was like 10-15 lbs. never could get the temp up higher than like 250  F, a friend sent me his tank for free I just had to pay shipping. but never got anywhere so far. it will most likely be when I retire LOL

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  • 1 month later...

 

Here is an interesting research paper comparing different thermal modification processes.  It is guitar based, using Sitka Spruce. There is not a lot of information regarding the tested processes; only temperature/time.  

Free download here:

(PDF) Comparison of different techniques of thermal modification, regarding the improvement of acoustical properties of resonant soundboard material Scientific Report by order of Pacific Rim Tonewoods Inc (researchgate.net)

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In the world of metals, protecting the metal from oxygen is done in a number of ways. The temperature is at a lot higher degree than for torrefied wood. Inert gases are not necessary and they are expensive. Nitrogen would work very well. You could first create a vacuum to remove internal oxygen from the wood and then back-fill the chamber with nitrogen and then raise the temperature. 

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6 hours ago, DavidS said:

There is not a lot of information regarding the tested processes; only temperature/time.  

There are also gaping holes in the information about the measurement of the wood properties, particularly how EMC of the test samples was controlled.  The samples are quite thick (30mm), and would take a long time (months) to reach a stable EMC after whatever wild swings would occur in the processing.  Nowhere does it mention anything about the relative humidity of the testing or how the samples were stabilized.  While this might not be a huge factor for most properties, it is a biggie for measuring damping.  Maybe this was all done carefully... but there is no mention of it.

For the wood processing itself, pressure is an important parameter that is not listed.  Perhaps for guitar wood in big chambers, they can't be pressurized, so atmospheric pressure is assumed.  We don't know.  I have seen some "torrefication" chambers for guitar tonewood that are obviously not pressurized.

As for the results, density, modulus, and R factor (Radiation Ratio), they all look about the range that I have been getting.  Damping, however, is unimpressive... small decreases and even some increases, where I have found that to be the largest change, averaging 18% decrease.

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6 hours ago, DavidS said:

 

Here is an interesting research paper comparing different thermal modification processes.  It is guitar based, using Sitka Spruce. There is not a lot of information regarding the tested processes; only temperature/time.  

Free download here:

(PDF) Comparison of different techniques of thermal modification, regarding the improvement of acoustical properties of resonant soundboard material Scientific Report by order of Pacific Rim Tonewoods Inc (researchgate.net)

Any idea it these tests were done at atmospheric pressure, and with oxygen present?

Don, what's the advantage of using pressure? Is it so that steam can be used to displace oxygen?

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6 minutes ago, David Burgess said:

Any idea it these tests were done at atmospheric pressure, and with oxygen present?

Don, what's the advantage of using pressure? Is it so that steam can be used to displace oxygen?

As far as I know, all torrefying is done with oxygen excluded, often by just pumping lots of steam into the chamber.  Hot wood + oxygen at a minimum might cause surface darkening.  And you really wouldn't like a fire.

In researching papers on the topic, pressure is often used, and I have seen that results vary with pressure.  As to why, I only presume that more pressure = stronger reaction, although I don't have the wood chemistry background to say for sure.  I only know that it's a variable that makes a difference.

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