Heat pliage for tops

Charles Meadows

So the original Selmers had their tops bent over heat.

I have been a flatpicker for years and have played a lot of high end flat tops. Dana Bourgeois recently started using "heat torrefication" on the tops of his new "aged tone" series guitars. And in my estimation they sound much better than his older guitars. The idea is evidently to "cook out" everything but the cellulose and lignins to make the top lighter and better sounding.

I was actually surprised what a difference this made in sound.

Do those of you who have played the GJ guitars (Barault, DuPont Vielle Reserve, etc) with real heat pliage notice a big difference?

MichaelHorowitz

I'm not familar with the heat torrefication technique, but it sounds like an attempt to simulate the aging process of the top. A heat bent pliage is an entirely different thing as the heat is only used to bend the top, not to try and age it in anyway. The heat itself is less important than the bend it creates which is generally more extreme and positioned under the bridge, which differs from a forced top which has a shallower bend with an apex over the soundhole. The pliage tops are generally punchier with a faster attack. Forced top guitars are nice too (all the Favinos and most modern guitars are made this way,) as they generally have other qualities people like. But if you like a lot of volume and attack, than the pliage will really turbo charge the top and make that happen.

M

Bohemian

"torrefication" is a new age buzzword for cooking the tops. This has been done for years by one Finnish guitar making company. Only now has it rizen (risen) to the status of cryogenic treatment... freezing. Another gimmick like tone-rite.

noodlenot

i´m under the impression that most of the big boys "cook" their tops. Taylor and Larrivée, at least, do it. Like many things lutherie related, all kind of sonic benefits are thrown around and explanations abound, but what really makes it worth it for them - AFAIK and IMO - is long term susceptibility to humidity fluctuations. wood that is completely deprived of moisture and allowed to come back slowly to room temperature/humidity tends to move less with further humidity changes, which means less warranty work in the long run.

my 0,002.

HarryR

Noodlenot, Cooking wood for instrument making is not a new thing. I don't know exactly what process Bourgeois is using , but J.B Vuilllaume was baking Spruce for violin tops in the 1850's. The purpose is twofold. The baking dries and hardens the resins that remain in the wood after the moisture content has equalized. This is supposed to give the top a similar resonance to a well aged piece of Spruce. Most instrument makers know that wood continues to change over long periods of time, That is the reason M. Dupont uses 40 years old wood for his best instruments.The second reason is the wood takes on a darker, oxidized color which makes it look very old. Much more convincing than a top sprayed with "ageing toner". Vuillaume was famous making new "old" instruments and is suspected of creating some suspicious "old" violins, including the famous "Messiah" Strad which is in the Ashmolean Museum. Violin repairmen who work on these instruments are allways cautioned about how they handle these tops as the wood often has become soft and punky over time.It appears that force "ageing" the wood can have adverse effects on the integrity and longevity of the wood. This may not be as important a factor in guitars as they don't seem to have nearly as long a lifespan as a violin, which can, and do have a life of several hundred years. Harry

noodlenot

Hi Harry. Yeah, nothing new under the sun, it seems. Didn´t know Villaume was doing it, thanks for the info. I´ve read that Martin did it back in the 30s to, but i don´t remember the source, could be my memory playing tricks.
I don´t have experience baking tops, mainly because my kitchen oven is to small for it but i was intrigued by it in the past and talked to several builders about it. The consensus amongst them was that the main benefit was long term stability with regard to humidity changes, although several mechanisms were proposed for it (changes to the structure of the cellular membrane or, as you said, crystallization of the resins, or maybe some other mechanism i´ve forgotten since). My problem with the resin thing is that resin is just a small (actually very small) and variable part of the top plate, and is localized on the resin canals, so anything that happens there will leave vast portions of the wood unchanged.
Regarding tone changes most (if not all) of the folks were skeptic (as i am, really) that it would actually improve tone in some discernible way, but experiments to prove these kind of assessments are typically hard to put together and scrutinize unbiasedly.
The thing you pointed out about "force aging" wood making it more fragile caught my attention and actually makes a lot of sense to me. Wood is mainly cellulose (roughly 50%), hemicellulose and lignin, as was stated above. Hemicellulose is the responsible for wood being hygroscopic, but doesn´t add much structurally after the tree is cut. It naturally tends to decompose over time, and that´s the main chemical difference between aged and young wood, but it takes a lot of time to do so. Lignin, on the other hand, is much more stable and plays a part on wood integrity and stiffness. Problem is that both lignin and hemicellulose get destroyed with heat (lignin at an higher and broader temperature interval than hemicellulose, but there´s overlap between them), so if you bake your tops at too high temperatures it should compromise their structural integrity. This is one of the reasons folks tend to cook their tops at lower temperatures for longer periods of time.
Sorry for the off-topic folks.