Stability of Torrefied Tops

User avatar
DenverSteve
Posts: 82
Joined: Thu Jan 02, 2020 4:10 pm
Real Name: Denver Steve
Location: Based: Denver, Operational: Worldwide
Contact:

Stability of Torrefied Tops

Post: # 1965Post DenverSteve
Thu Jan 02, 2020 4:34 pm

I've purchased a couple of baked/cooked/torrefied-topped guitars over the past few years because of their tonal characteristics. They are/were simply wonderful guitars. However, while reading a bit more on torrefied tops I found the below statement at Sweetwater. I know every builder that bakes their tops does so somewhat differently but, without concern about appearance or tone, do any wood-gurus have knowledge as to whether this statement is partially or completely true?

"Torrified (also spelled “torrefied”) wood neither swells up during humid summer months nor dries out due to dry winter air. Torrified wood will not shrink, warp, expand, or contract due to changing weather or humidity levels. Torrified wood has been heat treated or roasted until it has nearly 0% internal moisture."

If it is mostly or completely accurate, it would be a bid deal for anyone living in humid or dry regions. I don't see any torrification-specific information on the Collings site about this.
Shalom, Steve
A Few World-Class Tools..........

User avatar
DenverSteve
Posts: 82
Joined: Thu Jan 02, 2020 4:10 pm
Real Name: Denver Steve
Location: Based: Denver, Operational: Worldwide
Contact:

Re: Stability of Torrefied Tops

Post: # 1978Post DenverSteve
Thu Jan 02, 2020 6:46 pm

Additionally, this comes from PremierGuitar:

"The resulting wood boasts greater stability—especially beneficial as it’s exposed to atmospheric moisture during the life of an instrument—due to the closure of the cells when the water and sap is released from the wood. Another benefit is the beautiful golden-caramel color that results from the process. This is really nice as it relates to guitar tops, since the color comes out looking like older guitars with perfectly time-aged spruce."
Shalom, Steve
A Few World-Class Tools..........

User avatar
DenverSteve
Posts: 82
Joined: Thu Jan 02, 2020 4:10 pm
Real Name: Denver Steve
Location: Based: Denver, Operational: Worldwide
Contact:

Re: Stability of Torrefied Tops

Post: # 1979Post DenverSteve
Thu Jan 02, 2020 7:38 pm

Wow. I'm going to have to keep answering my own question if you don't pipe up. :D However, this video is extremely telling. Watch the whole thing - it's great. However, if you're busier than the rest of us, start at the nine minute mark and watch for a minute.

https://www.youtube.com/watch?time_cont ... =emb_title
Shalom, Steve
A Few World-Class Tools..........

Frank Sanns
Posts: 147
Joined: Sun Oct 21, 2018 5:38 pm
Real Name: Frank Sanns
Location: Pittsburgh

Re: Stability of Torrefied Tops

Post: # 1980Post Frank Sanns
Thu Jan 02, 2020 10:41 pm

I think most of the people in the know actually keep quiet. Torrefied wood is a little like politics and religion. It is better not to talk about it in public.

With that said, I can give some background on the wood. Baking wood has been used in Scandinavian countries amongst others to make wood more weather resistant. It is less hygroscopic (less susceptible to pick up moisture) than unbaked wood so it tends to not expand and contract as much from moisture. The moisture content is not zero in baked wood but it is lower than in non baked wood.

Tars, pitches, resins, and other materials exit the wood during the baking. The wood itself also starts to pyrolyze a little. This is actually why it does not pick up as much water as some of the water liking molecules in the wood are changed or removed. The remaining wood is more dimensionally stable with humidity changes. It also is stiffer but also weaker. Many luthiers found this out the hard way with bridge lifting on their guitars. For this reason, most luthiers no longer use hide glue on bridges of guitars with baked tops.

Baking changes various woods and even subspecies of woods or even different lots of woods a little different. I cringe a little when I see large lifts of wood being put into a large oven together with other pieces that are unique to themselves. Some outstanding pieces get lumped in with the pack and the results come out pretty much like the rest.

It is also not accurate to say that torrefied wood is the same as old wood. That is simply not true. It is not true chemically, structurally or tonally. I have said it many times and I will repeat here. It is a different means to a different end.

Some people like the characteristics of baked wood and others do not. As I said, it is a highly controversial subject on which people prefer but the facts are the facts. You either like it cooked or not.

User avatar
Haasome
Posts: 138
Joined: Fri Oct 19, 2018 2:21 am
Location: Massachusetts

Re: Stability of Torrefied Tops

Post: # 1981Post Haasome
Thu Jan 02, 2020 11:28 pm

Frank Sanns wrote: Thu Jan 02, 2020 10:41 pm I think most of the people in the know actually keep quiet. Torrefied wood is a little like politics and religion. It is better not to talk about it in public.

With that said, I can give some background on the wood. Baking wood has been used in Scandinavian countries amongst others to make wood more weather resistant. It is less hygroscopic (less susceptible to pick up moisture) than unbaked wood so it tends to not expand and contract as much from moisture. The moisture content is not zero in baked wood but it is lower than in non baked wood.

Tars, pitches, resins, and other materials exit the wood during the baking. The wood itself also starts to pyrolyze a little. This is actually why it does not pick up as much water as some of the water liking molecules in the wood are changed or removed. The remaining wood is more dimensionally stable with humidity changes. It also is stiffer but also weaker. Many luthiers found this out the hard way with bridge lifting on their guitars. For this reason, most luthiers no longer use hide glue on bridges of guitars with baked tops.

Baking changes various woods and even subspecies of woods or even different lots of woods a little different. I cringe a little when I see large lifts of wood being put into a large oven together with other pieces that are unique to themselves. Some outstanding pieces get lumped in with the pack and the results come out pretty much like the rest.

It is also not accurate to say that torrefied wood is the same as old wood. That is simply not true. It is not true chemically, structurally or tonally. I have said it many times and I will repeat here. It is a different means to a different end.

Some people like the characteristics of baked wood and others do not. As I said, it is a highly controversial subject on which people prefer but the facts are the facts. You either like it cooked or not.
Great post Frank. My experience with it has been limited. But as a wood scientist who’s looked at this material in a research setting, I share the the opinions laid out in your summary. I would add that we found Torrefied wood to be brittle, prone to crack, and can be tricky to machine cleanly. Also, it can be difficult to glue and finish — for the same reason it is less hygroscopic. It is a little stiffer, but I think it’s a little stiffer because it is a little “dryer.“ As you pointed out, I typically hold back on these discussions because my experience has been researching wood that has been heated at higher temperatures than what I think Guitar wood is treated. I have no real lab bench experience with guitar wood. My personal bias is that torrefaction, at the very least, degrades wood to some degree.
Paul

User avatar
DenverSteve
Posts: 82
Joined: Thu Jan 02, 2020 4:10 pm
Real Name: Denver Steve
Location: Based: Denver, Operational: Worldwide
Contact:

Re: Stability of Torrefied Tops

Post: # 1983Post DenverSteve
Fri Jan 03, 2020 12:21 am

Frank Sanns wrote: Thu Jan 02, 2020 10:41 pm Some people like the characteristics of baked wood and others do not. As I said, it is a highly controversial subject on which people prefer but the facts are the facts. You either like it cooked or not.
Thanks for your input. I like some baked guitars and love others. I actually purchased one of Martin's first released OM-28's with a cooked top and didn't particularly like it. Then there's the D-28 Authentic 1937 that is superb. My Collings D1 with baked top is also a great guitar.
Shalom, Steve
A Few World-Class Tools..........

Derek
Posts: 24
Joined: Sat Nov 10, 2018 6:50 pm

Re: Stability of Torrefied Tops

Post: # 1985Post Derek
Sat Jan 04, 2020 3:25 am

Only thing I have heard said is that the bridge does not glue to the top quite as securely.

RTA48
Posts: 1
Joined: Wed Oct 31, 2018 11:25 pm

Re: Stability of Torrefied Tops

Post: # 2001Post RTA48
Wed Jan 08, 2020 2:41 am

Earlier in the guitar cooking days several makers tried using totally torrified woods (back & sides) most quickly found that bending the side pieces was an adventure at best. % 0f breakage was very high so they discontinued that experiment. Today there are a few custom builders that still offer torrified backs, since its commonly thought that back & side woods play a minor role in overall tone that seems to keep cooked back pieces to a minimum.

I have owned several guitars with torrified tops, the early cooked Martins I felt were over cooked (whatever that means) it didn't take them very long to back off on their process. The skunk stripes of the early Martin tops were controversial at best. It seems to me that most of the larger manufacturers have settled on a process that does not degrade the appearance. I enjoy the tone of some torrified tops but as a general rule I prefer the none cooked tops.

Randy

armdog
Posts: 52
Joined: Thu Oct 18, 2018 2:13 pm

Re: Stability of Torrefied Tops

Post: # 2004Post armdog
Wed Jan 08, 2020 7:18 pm

+1 Frank
Not wanting to get into an expensive guitar to wet my feet, 27mos ago I bought an Eastman E20OM-TC (thermal cured red spruce). Turned out to be quite a good guitar, was 'played-in' day one. My 2008 CJ Mah/Adi was stiff new and only in the past couple years has it become 'played in', it's just great these days. Long term, who knows but at my age I go for the 'played-in' thing.

All them little lignins dancing around in tonesville. :)

User avatar
elambo
Moderator
Posts: 158
Joined: Fri Oct 12, 2018 5:48 am

Re: Stability of Torrefied Tops

Post: # 2005Post elambo
Thu Jan 09, 2020 4:27 am

It's always been an interesting topic. Opinions vary greatly, and can be quite strong (for *or* against). It's also difficult to test apples-to-apples, for obvious reasons. Regarding stability specifically, I tend to defer to Frank S. as this topic is firmly in his wheelhouse.

On that note... Frank, would you say that torrefied wood is less likely to split after being subjected to a rollercoaster of humidity dips and rises? I'm not referring to glued components, just a solid slab of wood like the back or top. You'd mentioned that it becomes stiffer but also weaker -- I'm wondering what (other than a bridge needing special care when being glued) you meant by that.

Post Reply