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Old 01-22-2020, 09:29 AM
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Default Trusting torrified spruce

Hey fellow builders. I bought some torrified adi spruce bracewood. I'm not convinced that it is as trustworthy as my non torrified adi bracewood. Tapping on an equally sized hunk of torrified spruce rings with similar volume and sustain as tapping on the nontorrified hunk of adi. It's clear that the torrified wood has been through a lot and I'm wondering if any damage was done that would affect the long term durability of a top brace under stress. Are the benefits of torrified braces worth whatever uncertainty such treatment brings. If anyone uses this bracewood and could comment on the risk/benefit outcomes I would love to hear about it.
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Old 01-22-2020, 10:00 AM
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One piece of chocolate cake as compared to the whole cake. One may make you go away feeling rather good about yourself where the other may make you debate doing it again. Same with treated wood, how long was it treated for? I have lightly done wood for braces. Braces are a fraction of the weight of the whole top, I do not see too much reason to do them.
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Old 01-22-2020, 10:14 AM
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I have read that T-spruce is stiffer than non-T-spruce, but will fail catastrophically at 70% of the load. In other words, it is stiff until it breaks unexpectedly under a smaller stress than expected. Personally, since I do my work largely by feel, this is counter intuitive and wouldn’t suit me at all. If one worked with deflection testing instead, it seems to me that the data would be skewed in a way that would require a complete revision of the formula. The bracing would be to be more delicate to get the same response, but that would make the guitar even more vulnerable. I love my Adi bracing because I understand it!
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Old 01-22-2020, 11:50 AM
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Originally Posted by Bruce Sexauer View Post
I have read that T-spruce is stiffer than non-T-spruce, but will fail catastrophically at 70% of the load. In other words, it is stiff until it breaks unexpectedly under a smaller stress than expected. Personally, since I do my work largely by feel, this is counter intuitive and wouldn’t suit me at all. If one worked with deflection testing instead, it seems to me that the data would be skewed in a way that would require a complete revision of the formula. The bracing would be to be more delicate to get the same response, but that would make the guitar even more vulnerable. I love my Adi bracing because I understand it!

I build like you Bruce. I build mostly by feel anymore. If you went with deflection testing on torrified spruce it would lull you into building in failure by your reckoning which I guess is what my concerns were. I'm thinking that this spruce might work well for back bracing since the loads are less and the contributions of the braces to sound production are different too, being more disciplinary in nature.
Its interesting that you use adi for braces. I do that as well in all my builds. It's one variable that I try to keep constant.
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Old 01-22-2020, 12:27 PM
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It is just a question of what you are used to and if you want to adjust for the material. If you were going to go forward and use a lot of baked braces then you build with it's properties. If you just want to dabble then view the guitars as experimental in nature. I am one to try different things just as a learning experience. I would be hesitant (and it shows you are also) to go out on a limb when you have a successful formula already.
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Old 01-22-2020, 01:27 PM
Halcyon/Tinker Halcyon/Tinker is offline
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FWIW...

I've built close to 30 guitars with torrefied tops so far.

I dropped torrefied bracing long before that because I did not like how it carved. And while bracing is absolutely critical to the final result, the downside difference in strength compared to the relatively minor upside difference in mass of torrefied vs non torrefied was not enough to to compel me to get over the hinkiness of the feel of torrefied bracing. It carved like driftwood and raised my hackles, which, despite being very math oriented in my work, is something I still trust, at least until proven wrong.

When you consider that the majority of the top assemby's mass (excluding bridge) is the top itself, the mass of the bracing takes a backseat. And the small savings of mass with torrefied bracing, for me, failed the risk/reward test, so I returned to regular bracing for torrefied tops. And there was no hearable difference between torrefied/non for bracing, unlike the top itself which is dramatically different in tone.

That being said, none of my torrefied braced guitars have failed, at least to my knowledge, and they've been out there for quite some time now, 5-8 years or such? So there's that too.

I would like to add one more thing.

I read sometimes that torrefied wood is stiffer. I don't believe that. It's been a long time since I've hit my notes, which have been lost to the Safe Place, but, to the best of my recollection...

I sent off a batch of tops to be torrefied with careful before/after note taking. They all came back with larger deflection numbers than they were sent with. So the process made them less stiff. But they also came back less dense, moreso than the difference in deflection,

So, while you can get the very same piece of wood to have less mass at the same stiffness, torrefaction does not stiffen the wood

Hope that makes sense...
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Old 01-22-2020, 02:10 PM
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I just built two with T Red Spruce a couple months ago and I used T REd Spruce bracing. I agree the stuff is weird and 'drift wood' is a good way to describe it. I just thought it would do a disservice to a T top to not use T bracing. At the recommendation of several other well respected luthiers I used Fish Glue for the bracing and clamped for 24 hours.

I do use deflection and found that these tops were actually pretty darn stiff. So they were made thinner then I normally would go.

One was an OM the other a small parlor guitar. They both were for one client. The OM came out fantastic. Truly one of the better instruments I had ever made and the client was super happy. The parlor was ok, not great, but still a good guitar.

In the end I'm not sure Id be able to tell that it has some super special properties. They are guitars and they sound like guitars.

So yeah, I understand your question. I have two out in the wild now only 3 months old and I am still nervous about them. But I've got two more on order too so it goes.
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Old 01-22-2020, 04:15 PM
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I worked for a number of years for a tonewood supplier doing all of the re-sawing, as well as most of the other hands on aspects of making lumber and pre-cut top sets salable (trimming/sanding). We would get spruce tops in and then send them out to get them torrefied. I found that when these tops came back they were definitely a bit lighter. I also noticed that they tended to be much more brittle in nature compared to non torrefied tops. I definitely believe that with an decent impact to the top, these torrefied tops will crack easier. Regarding gluing properties, it remains to be seen how the glue joints in this wood will hold up in the future, many years out. This information should translate to bracing also. I for one feel no need to use torrefied tops or bracing unless a customer requests it.
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Old 01-22-2020, 05:13 PM
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I just don't think that it's possible to answer this question in the abstract. There's torrefaction and then there's torrefaction.

Folks who torrify wood dramatically vary the duration and temperature of the process. I've been studying and researching the process, including interviewing those who torrify and those who use torrified woods in lutherie (FJ article on the horizon). These are early days in my research, but I can give a short summary: too much of a good thing is, indeed, too much of a good thing.

Stay tuned. I'll be running a bunch of torrified tops through a CT-scanner.

On edit 1: a post script. I've been stunned to learn the number of luthiers who purchase and use torrified wood without even inquiring about the process used to treat the tops (and sometimes backs and sides) that they purchase.

On edit 2: oh, the CT-scans will give me good data and cool pics. But, I've also arranged for MRI sessions, which will give a great deal of additional data about density, mass, brittleness, etc.
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Old 01-22-2020, 06:32 PM
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Originally Posted by jt1 View Post
I just don't think that it's possible to answer this question in the abstract. There's torrefaction and then there's torrefaction.

Folks who torrify wood dramatically vary the duration and temperature of the process. I've been studying and researching the process, including interviewing those who torrify and those who use torrified woods in lutherie (FJ article on the horizon). These are early days in my research, but I can give a short summary: too much of a good thing is, indeed, too much of a good thing.

Stay tuned. I'll be running a bunch of torrified tops through a CT-scanner.

On edit 1: a post script. I've been stunned to learn the number of luthiers who purchase and use torrified wood without even inquiring about the process used to treat the tops (and sometimes backs and sides) that they purchase.

On edit 2: oh, the CT-scans will give me good data and cool pics. But, I've also arranged for MRI sessions, which will give a great deal of additional data about density, mass, brittleness, etc.
So interesting, John - I just sent a PM Cheers, Dave Olson
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Old 01-22-2020, 06:58 PM
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Quote:
Originally Posted by Bruce Sexauer:
"I have read that T-spruce is stiffer than non-T-spruce, but will fail catastrophically at 70% of the load. In other words, it is stiff until it breaks unexpectedly under a smaller stress than expected. Personally, since I do my work largely by feel, this is counter intuitive and wouldn’t suit me at all. If one worked with deflection testing instead, it seems to me that the data would be skewed in a way that would require a complete revision of the formula. The bracing would be to be more delicate to get the same response, but that would make the guitar even more vulnerable. I love my Adi bracing because I understand it!"

From John K:
"I build like you Bruce. I build mostly by feel anymore. If you went with deflection testing on torrified spruce it would lull you into building in failure by your reckoning which I guess is what my concerns were. I'm thinking that this spruce might work well for back bracing since the loads are less and the contributions of the braces to sound production are different too, being more disciplinary in nature.
Its interesting that you use adi for braces. I do that as well in all my builds. It's one variable that I try to keep constant."

You guys rock. Both of you build the way I like to play. Different every time, and how it feels good today... at least that is the vibe I pick up from both of you!

It will be interesting to see what John Thomas has to add once he gets the data from the scans, etc.

John, what you are doing sure works for me!

Have fun at B.I.G.er gentlemen!!! I expect some interesting cross pollination may occur...

Paul
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Old 01-22-2020, 07:16 PM
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Originally Posted by jt1 View Post
I just don't think that it's possible to answer this question in the abstract. There's torrefaction and then there's torrefaction.

Folks who torrify wood dramatically vary the duration and temperature of the process. I've been studying and researching the process, including interviewing those who torrify and those who use torrified woods in lutherie (FJ article on the horizon). These are early days in my research, but I can give a short summary: too much of a good thing is, indeed, too much of a good thing.

Stay tuned. I'll be running a bunch of torrified tops through a CT-scanner.

On edit 1: a post script. I've been stunned to learn the number of luthiers who purchase and use torrified wood without even inquiring about the process used to treat the tops (and sometimes backs and sides) that they purchase.

On edit 2: oh, the CT-scans will give me good data and cool pics. But, I've also arranged for MRI sessions, which will give a great deal of additional data about density, mass, brittleness, etc.
The last time I had a CT scan, they found some torrefied spruce up there. But the doctor told me I’ve never sounded better.
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Old 01-22-2020, 07:23 PM
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Originally Posted by justonwo View Post
The last time I had a CT scan, they found some torrefied spruce up there. But the doctor told me I’ve never sounded better.
Alas, despite this diagnosis, well, you've never sounded good. (I love your playing.)

My central point is that luthiers buy and use this stuff without any knowledge of how the torrefaction was conducted. I've conducted many interviews. Luthiers simply state that they purchased torrefied wood, having no understanding of how it was torrefied.

Luthiers can ask two simple questions (there are many more variables, but these are the central 2): how long was it cooked, and at what temperature. These are critical questions, both for impact on tone and impact on durability/survivability of the guitar. Yet, very, very few luthiers ascertain answers to these questions before both buying and incorporating the purchased woods into a build.
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Old 01-22-2020, 07:33 PM
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Originally Posted by jt1 View Post
Alas, despite this diagnosis, well, you've never sounded good. (I love your playing.)

My central point is that luthiers buy and use this stuff without any knowledge of how the torrefaction was conducted. I've conducted many interviews. Luthiers simply state that they purchased torrefied wood, having no understanding of how it was torrefied.

Luthiers can ask two simple questions (there are many more variables, but these are the central 2): how long was it cooked, and at what temperature. These are critical questions, both for impact on tone and impact on durability/survivability of the guitar. Yet, very, very few luthiers ascertain answers to these questions before both buying and incorporating the purchased woods into a build.
And if they knew how it was cooked do they have the information to compare one process to another?
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Old 01-22-2020, 07:42 PM
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And if they knew how it was cooked do they have the information to compare one process to another?
Absolutely.

But, the process begins with the luthier asking how the wood was cooked and then discussing the wood parameters with then client. Anything less is fraudulent.
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