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Describing working properties and physical characteristics of timber can be almost as problematic as describing tone. With that in mind, I thought it might be interesting to try to get a bunch of descriptions of torrefied spruce all in one place. Torrefication is all the rage and it is my impression that many of us don’t really have a handle on what the wood feels like or how it works (let alone any tonal implications). I’d like to see some of the people in the know describe what torrefied tops are like and how they work and perhaps try to relate that to what one would expect from a newer non-treated top. If possible, try to keep this from becoming a debate about whether or not it is a good idea or what effect it may or may not have on a finished instrument. Even more so, let’s resist the urge debate the difficulty with getting useful data from comparing finished guitars.
I am a hobbyist and as such, have not handled any old spruce tops or torrefied spruce. Further, I still have a lot to learn about wood characteristics and identification in general. I, for one, don’t have a well-developed vocabulary when it comes to describing various woods. I have casually followed the discussions about these tops but not spent much energy on them because I didn’t see myself ordering any in the near future (I build slowly and have plenty of regular tops waiting for me). Then I go to thinking about some spruce I have in my stash that has always seemed off to me. I cut up an old exterior spruce door for brace-wood. I even made an ukulele top from it. I could tell it was spruce but with my limited experience, I could not tell what kind. It seemed like Sitka but different somehow. It was darker, and not quite brittle or crumbly but certainly carved differently than I expected. When I made the uke top, I even questioned that it was spruce at all because I discovered that it was not translucent like the other spruce I have.
This door had been fending off the elements for 35-40 seasons and here in St. Louis, it would have seen very hot and very humid summertime conditions and cold dry winters with wet springs. Our climate is also famous for drastically and frequently changing conditions. I have fond memories of snowball fights in shorts and t-shirts from my youth. Certainly this wood is well seasoned. Could it be that I do have a sample similar to torrefied wood or am I just way out of my element here? One other curious note about this wood, this is the only bridge I have had come off (HHG) and with its nylon strings it has seen much less tension than my other instruments. Are there gluing protocols for dealing with old/torrefied wood?

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I have used this on a number of guitars and I only used the Red spruce. I am also familiar with Martin as I live close by and as a repair center I get to see and hear what they are up to.
My experience is that it is a lot like old wood. Even smells different more from the heat I guess. The wood will be a bit different from raw wood. It seems more feathery and it does take a different glue technique. I allow at least 8 hr clamp time using fish and HHG. Even tite bond takes a bit more. I know a few guys using CA but never was a fan of that for spruce.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

John, what are they using CA for?

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Say what you do, Do what you say.

I just checked the torrefied red spruce top wood I bought and it's opaque. No light shines through it.

Interestingly, I'm retopping an 1967 guitar with Sitka spruce top and the color of the old spruce is pretty close to that of the torrefied wood. The old spruce top still shows light through in some spots whereas the torrefied red spruce is completely opaque.

Nathan and I were over at Wayne Henderson's shop the other day with some Red Spruce we cut last year. Wayne had a single torrefied Red Spruce top there, and we (Nathan, John Arnold, Don Wilson, Wayne and I) were all curious to see what we could figure out about the stuff. So, Wayne cut and sanded one of our tops (now Don's top) to the exact dimensions of the torrefied top, and we all took turns thumping on them--even sharing tips on tapping technique to ensure that we all found a node and had a similar experience.

The tops weren't cut consecutively from the same billet, so this obviously wasn't a perfect experiment, but it's the best comparison I've been able to make thus far.

Anyway.. we each decided that the torrefied wood was quite different. It's not more like old spruce.. It's just different. I will note that it tapped at a considerably higher frequency than our top, and it was quite stiff (about as stiff as the tops we brought--that's saying a lot). Though, I can't be sure that it wasn't just as stiff before it went in the oven.. And the higher frequency may just be a result of the difference in stiffness or the hardened pitch which can be achieved with some time.. or quickly in a conventional oven.

We'll be sending 50 or so tops to a well-reviewed torrefaction kiln this week. I plan to include a couple of unmatched halves for before and after comparisons (I'm particularly interested in comparing the fancy stuff to mom's classic oven-baked), so I may have more to add in a few weeks.

Until then I'll be taking orders for torrefied red spruce!

-Matt

Ah, this could get interesting. I look forward to learning more about these comparisons.

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George :-)

The metrics change very little. The only true comparison is before/after on the same sets of wood. So I'd gather data on 20 of those tops. Make sure they've been in climate and are stable. Measure the length, width, thickness, weight and tap freqs. Preferably make them dimensionally the same.

Then measure them again once they're back and have stabilized in the climate room til they're stable.

Then, there might be some valuable data. I have a half dozen that I collected data on to do exactly that, but haven't had time to do the post measuring.

I did come to the startling conclusion that I don't actually care about the stats, as the difference falls into the unquantifiable category. What I mean is that I already know that the metrics change very little, yet the difference between before and after is HUGE.

And can only be described as 'different'. I have 50 year old wood that I could not differentiate by tactile feel than something dried last week, and I don't think anyone else could either. I feel certain that I could pick out the torrefied stuff in the dark every single time, if even just by the fact that it smells like brown sugar. But it feels very, very different. The tap tone is very open and sonorous, whatever that means.

We've only finished one guitar with it so far, which can be briefly seen in the video we linked to the other day under 'good for a laugh', though we don't really play it much, it's mostly me talking out my soundhole. But I did get some clips which I plan to put up at some time...

Shameless bump

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

The reason for the torrefied process is to give tonal properties similar to 60 to 70 year old wood. Quite obviously the two aging process are very different if not in tonal results at least in induced trauma. We do not have the benefit of 50 years or so of experience using this wood(at least as far as I know). So it might be interesting to hear a guitar in 50 years time to see if results hold up. Some how I have a fear that structure will not stand up in the long run. No proof just my own opinion. Hope I am wrong.

Tom
h l a
e d n

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A person who has never made a mistake has never made anything!!!