Official Luthiers Forum!

Here is the latest Luthier Tips du Jour video - The topic is torrefaction and how it is applied to tonewood.
This video as well as all my other videos are available via my website, http://www.obrienguitars.com/videos , LMI's website or on youtube.
Enjoy!

Is it Torre-ah-fah-cation or Torre-ah-fac-shun?

Also, is there any hard science behind the claim that when it comes out of the oven it's the same as a piece of wood that is 25 years old?

Is it the same as a piece of wood stored for 25 years or does that 25 year old wood have to have been vibrating on a guitar?

It's torrefaction (fac-shun). The one problem I have with torrefaction is when people claim it replicates whatever it is that happens in a piece of wood in a guitar that ages naturally for many decades. There is no proof to back up that claim. The reason is simple. It's not even known exactly what the physical relationship, if any, is between what happens in a naturally aged piece of wood in a guitar and the supposed enhanced tonal characteristics that many people believe go with that. It's beyond me how anyone can claim that torrefaction replicates a process when that process is not even known. Maybe torrefaction actually does give a tone similar to a naturally aged piece of wood, but without knowing what the physical basis for the perceived tonal enhancement in naturally aged wood actually is, it is impossible to show or honestly claim that torrefaction acts by the same process.

And don't even get me started on the torrefaction time machine concept....

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

One characteristic torrefied wood does share with old wood is opacity.

I'm restoring a 1967 Ovation Balladeer for a friend. One of the jobs I'm doing is to replace the original top with a torrefied top. At first I was going to use new Sitka spruce, but after I got the braces on the top, we decided to use torrefied Sitka spruce and braces in an attempt to give the guitar the same sound it had with the 50-year-old wood. The reason we went with torrefied wood was because in 2004, Ovation introduced a re-issue of the original Balladeer guitars, but most are of the opinion that it doesn't sound as good as the originals, even though they both use the same tone wood and same brace pattern. What was missing was 40+years of aging.

So, here's the new wood candled under a bright shop light.



And, under a bright LED flashlight.



Next is the original 1967 top.





Finally, the torrefied Sitka spruce top. Completely opaque.





So, if based on opacity alone, the torrefied top is a lot older than 50 years. Maybe somewhere between 75 and 100 years old.

Here is the original top with the torrefied top wetted with naptha.



Here's what the torrefied top looks like after the final clear coat has been applied. There's no stain at all. Just natural color of the torrefied Sitka spruce under clear 2-part urethane finish.



And the finished product.





Here's a couple sound clips. The first is with Elixir extra light phosphor bronze and the second with Elixir extra light 80/20s. Please excuse my mediocre playing.

https://www.youtube.com/watch?v=gG9eTxwQcBM

https://www.youtube.com/watch?v=UNob_bMq4Ok

Here's an interesting paper published about using torrefaction to artificially age wood. It discusses both the wet method (autoclave) and the dry method (kiln) along the the advantages and disadvantages to both.

Characteristics of aged wood and Japanese traditional coating technology for wood protection
http://www.citedelamusique.fr/pdf/insti/recherche/bois/obataya-anglais.pdf

That's a interesting DanSavage and a nice looking top too!

Thanks. I bought the top and brace stock from Stewmac.

The color of that top looks great.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Thanks!

It sound every bit as good as it looks. Unfortunately, the cheap mike on the video camera doesn't really convey how it sounds in person.

Interesting. I have to say that the guy in the video does not seem to have a clue....he can't even pronounce "torrefaction". At any rate, he certainly does not understand the process. It is not simply "drying out" the wood. And while the environment is low in oxygen, mainly because no new air is allowed to enter, it is not done in a vacuum, as many folks seem to believe. And, no, the wood will not burst into flame at the temperatures it is treated at......way lower than you bake a at.

I am quite familiar with the process that much of the tonewood in the US is being treated with. I have seen and handled wood for acoustic tops, necks, electric bodies, fingerboards, etc., etc. both before and after treatment. I have helped load and unload the kiln with wood from many "top brand" guitar makers, acoustic and electric. I have stacks of this wood in my shop, tops, neck wood, brace wood, body billets, you name it. So, I do have a "hands-on" familiarity with it. Most of the wood being processed in the US is not done by the Torrefaction process, but rather the Thermowood process, two entirely different panted and licensed processed.

Yes this wood is different, but making the specific claims of what the various processes actually do to the wood relative to what natural aging does is a stretch, at best. There is a lot of marketing hype being tossed around, with no visible science to back it up. Claims that a particular piece of wood is just like wood from guitars x or y years old, is , IMNSHO, a lot of BS. That said, I do see many advantages of the treated wood. There is an obvious improvement in acoustic properties. Stability during humidity changes is definitely better. Shrinkage/swelling across grain appears to be reduced by over half. The visual properties of the color change is usually perceived as an improvement, though not by all.

I would suggest to just use a bit of common sense and don't swallow the hype without question....they really don't know the facts....yet.

Grant

Would you know which of those processes is used for the spruce tops that StewMac sells?

The research paper that Dan provided the link to above also points out that improved dimensional stability is an effect of heat treatment. That and the nice color would be two reasons torrefied wood would be of interest to me. However, while the paper presents data on changes that occur in a number of physical properties of cypress wood with natural age (up to hundreds of years) and in response to short dry or wet heat treatments, it doesn’t demonstrate that the changes in any of these properties, in either naturally aged or heat treated wood, have anything to do with the tone of a guitar.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Off hand, I don't, but I will ask John at Thermowood to see if he knows who is doing their wood. I need to run a batch down there next week, anyway.

As for the paper, since we really don't know how any of those numbers actually relate to how tops perform, it is really hard to speculate. Kind of goes back to your original comment.

I do know that tapping these tops is a whole different deal...almost like they are made of glass or metal. But, I have yet to string one up. I will comment more when I have.

Grant

I've been thinking about torrefaction of tonewoods for some time, and finally reached a conclusion. It's a cheat. It's a short cut. And it's a lie. It's a marketing ploy that will soon peter out.

It will not replace the wise selection of aged tonewoods, thoughtful job planning, and proper build techniques by a luthier with experience.

Just sayin.

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"Act your age, not your shoe size" - Prince

Well, we are all entitled to our opinions

Stringing one up tomorrow...Top, back, sides, neck, bracing, end blocks, and ebony bridge...all thermally modified.

Grant

Grant:
Please give us some feed back on the test run. I have a dread in process, along with three others with regular spruce so am hoping for some good news. Thanks in advance.
Tom

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

There's an interesting thread started last night on this subject over on the Acoustic Guitar Forum. Good original post about an experience trying out a bunch of guitars with torrefied tops at one location. The thread is already up to 4 pages of replies. What's interesting to me is that almost all the replies are from guitar buyers and players. Not builders. I think it's fair to say that a big majority have not taken the bait hook, line, and sinker about torrefaction being the next great thing in acoustic guitars. Many taking a wait and see attitude.

http://www.acousticguitarforum.com/forums/showthread.php?t=409537

My favorite quote:

"Torrified guitars lead to less money in your wallet and therefore more comfort when sitting."

_________________
Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

So I assume you made one simultaneously "exactly like it" with non-tor woods so as to make a valid comparison?

That's what I did when testing Roger Siminoff's component tuning theory --- in the end I was totally disappointed.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Nothing will replace 5-40 years of vibration and playing...and yes, that's my opinion.

Well, I finally got this strung up last night and played it for a half hour or so. Remember, it is newly strung up and this is the first playing, so......

I am very happy with it. Very rich full sound, lots of volume, and very much sustain (I know, not everybody likes that). This morning, I compared it to a several year old white spruce/cocobolo OM that has been played a lot and most think is a very good sounding guitar. The old one sounded quite thin in comparison to the new. For now, that is all I have to compare it to (no, I did not build a non thermally modified sister)

Now, this was built as a learning experience, and I am not trying to make any claims one way or another, but it does sound better than any other newly strung guitar I have built (BTW, I started building guitars in 1967).

Now, for a few comments that I hope will be helpful. Let me first state that the wood I am using is NOT Torrefied, it is treated via the Thermowood process using hot oil in radiators to heat the kiln. It is not done in a vacuum, in fact, there are computer controlled fans in the kiln to keep the heat distributed. This is approximately a 72 hour process with the maximum temp only being an hour or so of the cycle. If you have read the thread on the other forum from the above link, you see that somebody mentions that there are at least 4 different heat treating processes in use....and nobody seems to know the difference

I did read that topic and have a few comments, based on what I know from first hand experience. Let me preface this with the note that most comments in that thread seem to be hearsay or opinions with few first person facts....but that is about where this is at for now.

There were mention of gluing problems. I have found none. In fact, glue joints I have made seem better than most. On this one the blocks were thermally modified, too and when I shaved out the side wood for the end graft, I could not even recognize where the glue joint was...seemed like the sides and block were the same piece of wood. I have joined 3 tops and 2 backs and the joints are very good. Let me state that I use Elmer's Carpenter's Wood Glue, not Titebond...this glue bonds cocobolo rosewood very well with no extra messing around. I would not use Titebond on a guitar.

There are plusses and minuses. The with-the-grain strength does seem to be less, But not to the point that I feel it is a problem...you just need to be aware of it and treat the wood like any more crack prone wood (way better than Mexican crackwood). But even if you do get some splits, they are clean, follow the grain lines perfectly, and can be glued without showing.

One positive factor I find IS less shrink and swell across the grain. I do need to do some good tests, but a small informal test by a friend using sister slices of treated/non-treated spruce showed quite a difference. Exact 3" wide pieces which started at 5 or 6% moisture were placed in a 100% RH environment for a week. The non-treated piece swelled 0.100", the treated piece swelled 0.044", quite a difference, but I want to do more tests on my own with multiple samples and several moisture cycles.

I found the wood very easy to work with. The thermally modified HOG neck I used was the easiest carving neck I have ever done, and sanding was a breeze. I also noticed that binding channels in spruce fuzzed up way less when cutting across the grain.

I could go on, but in summary, I am favorably impressed and will build more.

One additional point is the big upcharge for using a heat treated top. Totally a rip-off. I can tell you that my costs (and this is for 300 white spruce tops and about 50 Lutz) ran about $10/top, and most of that was my time, so it is a relatively inexpensive process. And I won't even begin to talk about the marketing hype

So, I would say, don't be overly skeptical. This is just a new type of wood. Remember when almost all guitars were made of rosewood, mahogany, or sometimes maple?

Grant

Did a pine body, baked top and back, sides cracked when bending so I cut a new set and used it unbaked. Had no problem gluing with Tightbond although the glue seemed to bead up more. The guitar has been together for a few months and would not think twice about using treated wood. It is different but as Grant says if you think of it as a different type of wood you can then use it for its properties wherever it makes sense. Just another flavor on the spice shelf.