Gore Testing and Torrified Tops

[Elaine Seat]

I am starting a guitar with a torrified top. I also use Gore’s tapping and equations for determining top thickness.

Do the equations hold true for torrified tops the same as for non-baked tops?

Torrified tops are so fragile that I’m afraid to do much whopping LOL

Elaine Seat

[Elaine Seat]

As I have thought about it, I wonder if the torrified tops would use a different multiplier.

Has anyone used Gore’s method and also the whopping method and determined that the comparative top thickness is the same?

Or other way (math is OK LOL) to know the equations work the same?

[JohnParchem]

I have used Gore's method on torrified tops and think it is still applicable.  His tap method of determining the characteristics of the plate is still valid. The multiplier "vibrational stiffness" is set to your preference of the resonance you want in a guitar; that is why he has a set for steel string and a different set for classical. I use yet another set of values for Flamenco. The test is to use thickness to normalize the plate for a given guitar type. 

They are fragile and a little tough to glue as the torrified wood is slow to absorb water. I wet the top before gluing and leave the clamps on over night. I was not blown away by the wood and at least with one seller I suspected they torrified lower grade tops. I look at stiffness relative to density when selecting. My thought with torrified was that the density would go down (loss of moisture) and the stiffness would be at least as good. So I was hoping for a stiff low mass top. The characteristics of the torrified wood I had was average to below average compared to other spruce plates I had.  

[Elaine Seat]

Thanks John,

These are really helpful insights. Along with what you mention, I don’t care for the toasted color, and I think I’ll only be happy with covering it up in the finish with a color/stain.

I am going to check out a batch of tops later today, and you have given me good info to inform my purchasing decision.

I spent some time this fall talking with Uve Kruger (he is a Collings artist and plays Collings instruments) about guitars, and he really liked the torrified top instruments he had played. Of course, any guitar provided to him would be top of the line, and would have not been inferior wood to start with. He indicated that his opinion was that the torrified tops would be an incremental step in improving guitar quality. Thus, my interest in exploring torrified tops.

It was very helpful to me to chat with a professional who has spent years playing a lot of guitars in a search to find a better one. 

[Paul McEvoy]

I'm interested in what we have available at home....I know people have been baking tops in their over which is not a "true" torefaction, whatever that is.  But it would offer some more control and knowledge of what you had.  

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[JohnParchem]

I do agree that torrification can improve a plate by effectively ageing it. My comment were around the torrified plates I as able to get by ordering them online from major vendors. An incremental improvement of an average plate might not make it as good as a great top. So in my experience I paid extra for some average to just above tops. 

[Elaine Seat]

Paul,

I appreciate wanting to take action that can be done by us at home. Unfortunately, I don’t think torrification is readily achieveable at home. That said, baked tops might be an intermediate improvement.

I live near the Hampton Bros, suppliers to many guitar builders. I visited them last spring and talked torrified wood since they had a pile of tops available. Here’s what they told me.

Torrified wood is baked in ovens with a gas (I think Argon), so there is more than just baking. The process drives the oxygen out or the wood is my recollection, so maybe pressurized also.

The torrification process is at the billet level becuase it would be too much handling and unpredictability of warping for plates. 

They send off billets, and then resaw to plates when it comes back. It sounded to me like getting in the torrification business was a specialty that they preferred using folks that had experience and the investment to do it.

Their shop area with the torrified billets/blanks smelled like the woods after forest fire! 🔥 

Elaine

[Paul McEvoy]

yup!  I think torrefaction is probably different things to different people, but I realize home baking isn't it.

I think Don Macrostie does some variety of home torrefaction in his shop but I can't remember what the details were.

There was a podcast interview recently with someone well respected who was talking about baking tops and getting good results.  I don't really remember the details though.

I think it's this one, don't quote me:
https://luthieronluthier.libsyn.com/83-james-condino

Virus-free.www.avg.com

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Paul McEvoy
207-699-9526

[Elaine Seat]

John

I absolutely agree with you about torrification not making a good top from a not good top. I think your advice is really helpful. It is difficult to find suppliers that provide us with what we expect. I’m sorry you had a bad experience because it is an expensive and time consuming test to totally build a guitar to check out a technology, and then have a poor quality sample.

It seems that even if you are willing to pay top dollar for a great top, there is no guarantee that that is what it will be when it arrives. Perhaps the tops provided with sonic data will help with this problem.

I had someone provide me with 10 redwood tops for inspection, from rough stock cut in 1980. Two of them were stiff, and the rest were floppy at 6mm thick! Thankfully, I could send back what I didn’t want.

[Robbie O'Brien]

If you want to know more about how wood is torrefied, here is a video I did a number of years ago about the process. 

Luthier Tips du Jour Mailbag 106 - What is torrefied wood?

~ https://youtu.be/6g2crKx1D0g

Robbie

On Dec 9, 2023, at 9:30 AM, Elaine Seat <elain...@gmail.com> wrote:

John

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[Colorado Clem]

OK, I'll give you my opinion. I have built maybe seven or eight guitars with torrefied tops. Other than one red spruce top, all of them have been Sitka. I also have another ten or so torrefied tops in inventory. I agree with John, that pretty much every torrefied top I have purchased appears to have been processed from just ok wood to start with. It seems like vendors are taking their borderline wood and torrefying it with the hope it hides visual defects and may improve them sonically, but it's all a crap shoot.   

I have been using Gore's normal factor for steel string guitars. I do believe the numbers are valid. I have done the flop test and it comes in pretty much right on Gore's numbers. I am with John, that I don't see a lot of difference, density wise with Gore's method versus non torrefied tops. When I get all done, I have actually built my two best guitars with non torrefied tops. One is an an OM with a really excellent non torrefied Carpathian and the last build is a dread with Pacific Tone Woods sonically tested four piece back. 

I think Pacific Tone Wood is really onto something with their sonic testing. I'm tied up for a week, but I'll try to get something put together about my experience with PTW tops. 

[JohnParchem]

I also like the Pacific Tone Wood sonically graded tops. All of the standard grading is on looks. At the GAL I picked up a few select tops from  Pacific Tone Wood. Here is a video of me comparing their numbers to Trevor's tap method numbers.

https://www.youtube.com/watch?v=SoG0iopzKfw&t=8s

[Robbie O'Brien]

Nice video John.

Thanks for sharing.

Robbie

Lutherie Academy by O'Brien Guitars lutherieacademy.com Keep track of the changes going on now at O'Brien Guitars by signing up for my newsletter

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From: obrien...@googlegroups.com <obrien...@googlegroups.com> on behalf of JohnParchem <johnp...@hotmail.com>
Sent: Saturday, December 9, 2023 18:53
To: Robert O'Brien Guitar Building Forum <obrien...@googlegroups.com>
Subject: Re: Gore Testing and Torrified Tops

 

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