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I have been very interested in this stuff and have used it for a number of years. I will share what I have learned.

Toffirication is a process that changes the wood cell structure by controlled heat , and in that , the wood is taken to over 400F . As it gets near the flash point in an untreated oven it would burst into flames. The process uses a number of techniques to avoid this. In one steam is used another an inert gas like Nitrogen . So the process may differ the end result is similar . The hemocellous layer of the cell is changed. One characterization of this result is the physical change of the cell. It will not allow light to pass through and the cell doesn't take on water like raw wood.

So what does this mean ? I have found that scrapers will tear torrified spruce apart so don't even try. The wood tends to be a bit more brittle in that respect. I also learned that gluing Torrified wood take a different approach. I can say that HHG fish and tite bond all work but with 1 caveat. You need to increase the clamp time from a few hours to a minimum of 24 hr.
I prefer tite bond as this is a curing glue and seems to be a better biding agent on gluing the plates. As for bracing I also will do a 24 hr clamp time but with a wider glue surface area the braces glue very well with any wood glue.
Routeing the rosette is tricky as the wood is more chip prone so a good sharp bit is needed. I do use duco cement for all my rosettes and this seems to work just fine. I don't use CA but my history of using it was short because of the staining on spruce. I can't say it will stain Torrified but duco does fine.
As of for Tone I do find the torrified wood does have a more wood aged tone for my ear.

Binding , is the same process and again you want to use a sharp bit. I have use pearl , herringbone . wood and plastic purflings and binding. Can't say I say much of a difference in the process but I do suggest a multicoat of sealer. The tape can pull wood fibers and that can cause issues as it can pull them up for a long stretch and cause damage.

Finish is about the same I do like that the wood seems more stable in RH changes than raw spruce. I also like the old color tone change but some may not. So I hope this helps you . I do like that this offers another ingredient in the recipe of building a guitar.

Thanks for the information John. I am working on a torrified spruce top now and in particular on the rosette and I have seen the tearing you mentioned using a scraper. I think I am okay though because I had enough of a light hand and some extra wood thickness to be able not do any lasting damage. I will find out for sure when I am able to put it through the thickness sander.

I did put a wash coat of shellac on the top before routing the rosette, and I suspect that (and maybe my bit was sharp too?) helped me get away with no chipping.

I am interested in hearing what you mean when you suggest having a wider glue area when doing bracing. I already have my braces made at 5/16 so I'm hoping I can still use those. I will certainly change from using the fish glue I had intended to use to Titebond and lengthen the clamp time as you suggested.

Thanks.

when you look at the plate thickness of under 1/8 in and the braces are 1/4 ot more that is the glue surface area I was referring to

I've found that the dust produced from torrified tops is superfine and powdery. It's really irritating to my eyes and lungs. Although I'm sure that all of us wear eye protection and dust masks at all times (meant to be sarcastic), I really urge folks to wear a dust mask when doing a lot of sanding of a torrified tops, especially if you have a lung condition or you're sensitive to dust.

Rag Thumb wrote:Thanks for the information John. I am working on a torrified spruce top now and in particular on the rosette and I have seen the tearing you mentioned using a scraper. I think I am okay though because I had enough of a light hand and some extra wood thickness to be able not do any lasting damage. I will find out for sure when I am able to put it through the thickness sander.

I did put a wash coat of shellac on the top before routing the rosette, and I suspect that (and maybe my bit was sharp too?) helped me get away with no chipping.

I am interested in hearing what you mean when you suggest having a wider glue area when doing bracing. I already have my braces made at 5/16 so I'm hoping I can still use those. I will certainly change from using the fish glue I had intended to use to Titebond and lengthen the clamp time as you suggested.

Thanks.

I use 5/16" bracing on my tops and I've made several torrified tops. I use hide glue and I've had no problems with the bracing. I leave the top in the gobar deck for a minimum of 24 hours, sometimes all weekend.

in the case of torrified longer is always better

I appreciate the explanation of how torrefaction works. I had assumed that it was the same as natural aging in wood, but I think now it must be mimicking this. I was given a 30+ year old spruce top set, nice tone, and am looking forward to seeing if it will help me to get an "old guitar" sound a little sooner. Should I expect the same issues dealing with an old top like this as with a torrefied top?

Stray Feathers wrote:I appreciate the explanation of how torrefaction works. I had assumed that it was the same as natural aging in wood, but I think now it must be mimicking this. I was given a 30+ year old spruce top set, nice tone, and am looking forward to seeing if it will help me to get an "old guitar" sound a little sooner. Should I expect the same issues dealing with an old top like this as with a torrefied top?

I've not noticed the weird powdery consistency of the torrified wood dust when I've worked with old instruments.

As far as gluing, I've always clamped longer. I've made instruments from very old wood, but not the spruce. I increase my clamping time when I work with old wood. I noticed it was a little more resistant to gluing than new wood. I assume spruce would be the same.

I agree on the finer dust especially on red spruce.
Torrification is an old process that was actually done first by the Norse .Amazing how
ingenious our ancestors were . I find old wood also has a different smell . To me it always smells like an old attic floor

True. It does have an "old" smell. Torrified spruce doesn't smell like spruce. I always enjoy the Christmas tree smell of spruce when I work it; that smell also let's me know I'm down to bare wood. Torrified spruce doesn't have that smell.

I was trying to think of a comparison for the dust generated by torrified spruce. If you cook. It's like cocoa or corn starch, super fine dust that sticks to stuff.