I started a thread on TGP about wanting to learn more about this topic and picked up some knowledge. I'm going to try to share some of the best bits here:
https://guitar.com/guides/essential-gui ... refaction/
Many players are chasing vintage tone, but most of us would prefer not to pay vintage prices, and this has sparked a search for several ‘magic bullet’ solutions in the last few decades. The pachyderm in the parlour, however, is that for all the time and effort that goes into meticulously recreated pickups and parts, they are invariably screwed or glued onto instruments made from relatively fresh wood.
If we accept there is some truth in the belief that vintage instruments sound different to even the most exacting repros and reissues, it follows that the tonewood itself may be the determining factor. Most of the same woods that were used for pre-war Martin acoustics, 1950s Gibsons and 60s Fenders are still available and remain in common use. ‘Same wood but different tone’ suggests that wood changes as it ages.
This belief in the tonal superiority of old wood has led to some frankly regrettable ‘conversions’ of perfectly good vintage guitars. A more positive development has been the increased use of reclaimed timber. While this can be successful on a bespoke basis, reclaimed timber is not obtainable in sufficient quantities for high-volume guitar production.
Fortunately the aging process of wood is a long established field of scientific research that has been pursued well away from the myth-mongering of vintage guitar dealers and fondest fantasies of Les Paul enthusiasts. Now it seems that the missing piece of the vintage tone jigsaw may have been found.
The buzzwords you’ll doubtless have heard are torrefaction, roasting, tempering, caramelisation and rectification – but they all amount to the same thing. We’re talking about thermally treating tonewood to condense decades of aging into a matter of hours. The rationale is that if you can induce changes at a molecular level that make the physical properties of fresh tonewood more like its decades old equivalent, the tonal qualities will follow suit.
Although touted as the latest shortcut to vintage tone, torrefaction has been around since the Vikings invented the booze cruise. So what is it and why all the recent excitement
Burning Issues
Obviously tone wasn’t a big priority for Viking shipwrights. What they needed were strong seagoing vessels that would remain watertight. Even well-seasoned timber is susceptible to changes in temperature and humidity – especially when it’s frequently in and out of water.
The Vikings used torrefied wood because it absorbs less moisture so size and shape are more likely to remain consistent after it has been sawed and planed. In other words it’s stronger and more stable as well as being lighter, which means it’s equally well suited to shipbuilding, wooden flooring and guitar making.
Guitar manufacturers such as Rickenbacker have long been using heat-treated timber for this very reason – while making no claims of tonal superiority. In recent years, Gibson has utilised torrefied maple for some fingerboards as an alternative to rosewood.
The torrefaction process involves baking wood in an oxygen free environment at temperatures higher than conventional timber seasoning kilns. Taken to its logical conclusion you would end up with charcoal but stopped short, the wood merely darkens depending on how long it has been roasted.
This colour change occurs due to chemical reactions between the wood’s proteins and its natural sugars, and torrefied maple can range from soft amber to a deep reddish brown that is closer to cherry or even walnut. You can observe similar outcomes with spruce and the colour change permeates throughout the timber.
Growing Old Gracefully
Maine-based luthier Dana Bourgeois was among the first US luthiers to use torrefied timber. He told Reverb.com that freshly cut wood is mostly cellulose bound together with lignin and contains volatile elements including “pitches, sugars, oils, and… considerable water content”.
Regular timber seasoning reduces the water content but the goal is to ensure that any potential shrinking or warping takes place during the process, not once the guitar has been assembled. However, seasoning does not remove the volatile elements that supposedly dampen the resonance and slow down the wood’s transient response.
Bourgeois describes how, over the course of several decades, these volatiles eventually vacate the wood as they, “oxidise, gas off and mineralise. The slow chemical reaction emits a gas and leaves a mineral residue. The lignin also sets like glue, holding the cellulose together”. Once this has taken place, the timber should be lighter, stiffer and quicker to respond than when it was first used to build the guitar.
The Great Bake-off
Torrefying already seasoned wood speeds the process by cooking off the volatile contents of the timber and leaving behind the mineral residue. It also induces changes in the cellular structure that would otherwise take half a lifetime. Going from an open to closed cell structure prevents the wood from re-hydrating. In other words once it’s dry, it will stay dry.
Contrast this with seasoned wood that is dried to the point where the water vapour pressure in the wood and the surrounding ambient space are more or less equal. This is called ‘the equilibrium moisture content’ but since the wood remains hygroscopic, it can continue to release and absorb moisture depending on what the atmospheric conditions are.
When acoustic guitars dry out, the wood wants to shrink but the glue joints will try to hold firm. This is why cracks and splits can appear and it’s very common to see the evidence on old acoustics. Consequently we’re advised to keep all-solid guitars hydrated, but while this may help to prevent cracks from occurring, it also inhibits the ageing process described by Bourgeois.
Consequently your well-hydrated acoustic may sound excellent, and you should feel good about maintaining it properly, however you’re unlikely to hear ‘vintage’ sounds from it in your own lifetime. And if you try to force the aging process by drying out your guitar, it’s likely to develop structural issues.
This is a crucial argument for building acoustics with torrefied wood. Since it’s non-hygroscopic, torrefied wood is far less likely to expand or contract, meaning guitars will be less vulnerable to atmospheric conditions and less likely to crack.
Torrefied wood is also said to have the stiffness and quick tap tone response of decades old wood, so it sounds more ‘vintage’. Compared to seasoned but non-torrefied wood the tone is more consistent because it’s less susceptible to atmospheric conditions. These tonal benefits, rather than the improved stability, explain why heat-treated timber has moved onto the radar of electric guitar builders, too.
Taste The Difference
So, is it just a gimmick or is there something in torrefaction that goes beyond clever marketing? Although we haven’t conducted the kind of tests that would produce a raft of conclusive empirical evidence, several members of the team have formed opinions based on DIY builds and encounters with review instruments.
We recently used an Allparts one-piece roasted neck in a partscaster build and were mightily impressed with its look and feel. Despite a massive 50s profile it was light in weight, and when tapped the neck produced a pure note that rang for a full two seconds.
Although it ended up bolted onto a lightweight but non-torrefied swamp ash body, the guitar turned out to be one of the loudest, liveliest and most resonant T-style instruments we’ve ever encountered. This first experience building with torrefied parts was exciting to say the least.
On the electric side, our editor recently reviewed two of Dennis Fano’s new Novo instruments, both of which featured tempered pine bodies and roasted maple necks. He praised their acoustic volume and resonance and the Serus T even scored a perfect 10. G&B’s stateside correspondent Dave Hunter is also a fan.
On the acoustic side, this writer has recently encountered the Bourgeois D-Custom featuring a torrefied Adirondack spruce top and Alister Atkin’s banner headstock-inspired model, The Forty Three. The Bourgeois’ specialised voicing made it hard to assess whether its temperature-treated top had any ‘vintage’ sonic attributes, but the Atkin was an absolute revelation, even though it arrived hot on the heels of a Fairbanks take on a Gibson Nick Lucas and a couple of 1930s Gibsons that featured in Vintage Bench Test.
The Fairbanks is undeniably a superb acoustic guitar but there is nothing especially ‘vintage’ about its tone… yet. In contrast the Atkin genuinely sounded like a vintage Gibson straight out of the box, with a dark sparkle and arid woodiness that hitherto we hadn’t considered achievable with a brand new acoustic. Another guitar that was awarded top marks.
Although the findings of the G&B team were arrived at separately, they have ended up being very closely aligned. Long term structural stability is tough to assess but our experiences suggest that heat-treated tonewoods used in new acoustic and electric instruments can contribute significantly towards the kind of tonality and dynamic response more commonly associated with vintage instruments.
The Roasted | Baked | Carmelized | Torrified Wood Thread
THERMALLY TREATED WOOD IN MUSICAL INSTRUMENTS
by Pertti Nieminen, Taisto Pietilä, Pekka Suhonen Tampere University of Technology, Finland Laboratory of Engineering Geology
ABSTRACT
The aim of this study was to determine and verify factors affecting the most important properties (i.e.sound, durability and appearance) of wooden musical instruments and to follow the behavior of the completed instruments in a chamber where different weather conditions were simulated, as well as determining the correlation between thermal treat- ment and natural aging of the wood. Remarkable changes in the cell tissue were observed after thermal treatment. The heat seemed to cause a type of melting or crystallization phenomena on the wood surface. Also, hydrophility decreased considerably during the tests, which can be seen as a decrease of the balancing moisture. When inspecting the pore size distributions of different tree species before and after thermal treatment, one could observe an increase in the amount of the large (>1 micrometer) absorption pores and, respectively, a distinctive decrease among the small (<1 micrometer) water pores. Another change in the structure of the cell tissue of the coniferous tree is connected to the behavior of the so-called “ring-like” pores. Dried spruce, for example, has a surface structure where ring-like pores have been closed in connection with drying. Thermal treatment, however, will break these pores open. When comparing the surface structure of thermo-treated spruce with spruce dried naturally for one hundred years, a clear structural similarity can be observed, with a similar stiffness and velocity of sound attained. When measuring the sound velocities, thermal treatment seemed to have a significant influence on the attained level of the sound velocity. In low temperatures, (<200 C-grades), the velocity increases from 0-1000 meters/second. In temperatures too high for thermal treatment for musical instrument wood, (i.e. clearly more than 200 C-grades) the sound velocity begins to decrease respectively. Furthermore, the attained level of the sound velocity is dependent upon the density and initial moisture of the wood.
CONCLUSION
The results shown in this research are to be taken as guidelines. For example, the following features have been observed: When thermally treating tonewood, the length of the process and temperature play a significant role in the success of the method. It is important to take into consideration the differences between wood species. It was also observed that the inner factors, such as density and moisture content, affect the changes achieved through thermo-treatment.
It was clearly observed that the treatment temperature affects the achieved sound velocity of wood samples. Treatment in too low a temperature only dries the wood like conventional machine drying, producing no benefit for tonewood. For example, the sound velocity or weight of the wood does not change. Respectively, too high temperatures leave the tonewood fragile, making workability worse. In the correct temperature, however, there are several benefits: the wood stabilizes (ability to adsorb moisture decreases), stiffness increases, the weight drops, sound velocity increases, the wood color deepens, and the wood resonates better (partially because of the increased sound velocity).
Thermal treatment of broad-leaved (deciduous) and conifer trees differ from each other. Deciduous species such as alder or birch can be treated in higher temperatures to make them work very well as tonewoods. Higher temperatures change the structure of the conifer species (spruce, pine) to the extent that they do not work well for building musical instruments. Milder treatment maintains the natural elasticity of the conifer wood and the desired elements of good quality tonewood improve in the manner of natural aging of wood. The research results correlate well with the experience of the musical instrument makers co-operating in this study. The correlation between measured values and experimental data is significant when comparing the original qualities of the wood samples (growth speed, what season the tree was cut down, etc.) with the treated samples – sound velocity compared to tap tones and workability…
Through measurements and experimentally-built musical instruments, this research results in the conclusion that when thermally treating tonewoods in a specific manner observed, the changes in wood are the same as in naturally aged wood, whereas certain qualities of wood improve while the wood maintains its workability and strength. Further, the benefits of thermo-treatment seem more apparent among the higher quality wood species treated.
ISBN 952-15-0971-6
ISSN 1238-075X
Our sincere thanks to Juha Ruokangas and Professor Pertti Nieminen for providing English language transcripts of the abstract and conclusions.
Pertti Nieminen, Professor, Ph.D.
Tampere, Finland
So, is thermo-treatment really some kind of dark “voodoo” brewed in Finland by sunlight-deprived trolls with entirely too much time on their hands, or is it a truly important innovation of significant value in guitar construction? When we published an overview of the Plek machine with Joe Glaser in the January 2003 issue of TQR, we heard shouts of “snake oil!” too, yet the Gibson Custom Shop is now installing a Plek machine to dress the frets and cut the nuts in every guitar they build. Remember this – ignorance is fed by the fear and resentment of things not understood, and there will always be “experts” who refuse to believe that anything worth knowing could possibly have escaped their attention (because in their minds, they have nothing left to learn). And on that score, they will always be right.
Should Thermo-treatment become available in the United States (and we believe it will), you’ll hear about it first, right here.
TQ
ToneQuest Report, January 2006
Source: https://web.archive.org/web/20120319194 ... om/?p=1871
by Pertti Nieminen, Taisto Pietilä, Pekka Suhonen Tampere University of Technology, Finland Laboratory of Engineering Geology
ABSTRACT
The aim of this study was to determine and verify factors affecting the most important properties (i.e.sound, durability and appearance) of wooden musical instruments and to follow the behavior of the completed instruments in a chamber where different weather conditions were simulated, as well as determining the correlation between thermal treat- ment and natural aging of the wood. Remarkable changes in the cell tissue were observed after thermal treatment. The heat seemed to cause a type of melting or crystallization phenomena on the wood surface. Also, hydrophility decreased considerably during the tests, which can be seen as a decrease of the balancing moisture. When inspecting the pore size distributions of different tree species before and after thermal treatment, one could observe an increase in the amount of the large (>1 micrometer) absorption pores and, respectively, a distinctive decrease among the small (<1 micrometer) water pores. Another change in the structure of the cell tissue of the coniferous tree is connected to the behavior of the so-called “ring-like” pores. Dried spruce, for example, has a surface structure where ring-like pores have been closed in connection with drying. Thermal treatment, however, will break these pores open. When comparing the surface structure of thermo-treated spruce with spruce dried naturally for one hundred years, a clear structural similarity can be observed, with a similar stiffness and velocity of sound attained. When measuring the sound velocities, thermal treatment seemed to have a significant influence on the attained level of the sound velocity. In low temperatures, (<200 C-grades), the velocity increases from 0-1000 meters/second. In temperatures too high for thermal treatment for musical instrument wood, (i.e. clearly more than 200 C-grades) the sound velocity begins to decrease respectively. Furthermore, the attained level of the sound velocity is dependent upon the density and initial moisture of the wood.
CONCLUSION
The results shown in this research are to be taken as guidelines. For example, the following features have been observed: When thermally treating tonewood, the length of the process and temperature play a significant role in the success of the method. It is important to take into consideration the differences between wood species. It was also observed that the inner factors, such as density and moisture content, affect the changes achieved through thermo-treatment.
It was clearly observed that the treatment temperature affects the achieved sound velocity of wood samples. Treatment in too low a temperature only dries the wood like conventional machine drying, producing no benefit for tonewood. For example, the sound velocity or weight of the wood does not change. Respectively, too high temperatures leave the tonewood fragile, making workability worse. In the correct temperature, however, there are several benefits: the wood stabilizes (ability to adsorb moisture decreases), stiffness increases, the weight drops, sound velocity increases, the wood color deepens, and the wood resonates better (partially because of the increased sound velocity).
Thermal treatment of broad-leaved (deciduous) and conifer trees differ from each other. Deciduous species such as alder or birch can be treated in higher temperatures to make them work very well as tonewoods. Higher temperatures change the structure of the conifer species (spruce, pine) to the extent that they do not work well for building musical instruments. Milder treatment maintains the natural elasticity of the conifer wood and the desired elements of good quality tonewood improve in the manner of natural aging of wood. The research results correlate well with the experience of the musical instrument makers co-operating in this study. The correlation between measured values and experimental data is significant when comparing the original qualities of the wood samples (growth speed, what season the tree was cut down, etc.) with the treated samples – sound velocity compared to tap tones and workability…
Through measurements and experimentally-built musical instruments, this research results in the conclusion that when thermally treating tonewoods in a specific manner observed, the changes in wood are the same as in naturally aged wood, whereas certain qualities of wood improve while the wood maintains its workability and strength. Further, the benefits of thermo-treatment seem more apparent among the higher quality wood species treated.
ISBN 952-15-0971-6
ISSN 1238-075X
Our sincere thanks to Juha Ruokangas and Professor Pertti Nieminen for providing English language transcripts of the abstract and conclusions.
Pertti Nieminen, Professor, Ph.D.
Tampere, Finland
So, is thermo-treatment really some kind of dark “voodoo” brewed in Finland by sunlight-deprived trolls with entirely too much time on their hands, or is it a truly important innovation of significant value in guitar construction? When we published an overview of the Plek machine with Joe Glaser in the January 2003 issue of TQR, we heard shouts of “snake oil!” too, yet the Gibson Custom Shop is now installing a Plek machine to dress the frets and cut the nuts in every guitar they build. Remember this – ignorance is fed by the fear and resentment of things not understood, and there will always be “experts” who refuse to believe that anything worth knowing could possibly have escaped their attention (because in their minds, they have nothing left to learn). And on that score, they will always be right.
Should Thermo-treatment become available in the United States (and we believe it will), you’ll hear about it first, right here.
TQ
ToneQuest Report, January 2006
Source: https://web.archive.org/web/20120319194 ... om/?p=1871
The following is from John Suhr posting as Husky on TGP:
Here was my test.
I built a vulcanized neck 3 years ago with no truss rod.
Not once has it gone out of whack even through the Santa Ana Dry seasons, not fret sprout, still the exact same relief as it was when we made it. Then I took a cup of water and poured it on one side of a neck blank. Left it for the weekend and checked Monday, it didn't move at all. When I do this with untreated maple it will back bow. Now Roasted is half way towards vulcanized so no matter what it will be an improvement. It is not as brittle to work with as the fully bake version and has a prettier color. The major thing for me though is I love the way it sounds. It isn't about marketing because I cant get it that easily, it is about trying to offer some great product that decreases tech service calls on how to adjust the neck. It is also more dimensionally stable. I have a lifetime warranty, that is why I advise using it. In fact the next guitar I make for myself is a Roasted neck and Body.
As far as is it being snake oil? Hardly, it is only new in the use of instruments. Some acoustic makers have been treating their tops for decades.
Another benefit is weight is reduced and really opens up (my perception).
The organic sticky sap are all baked out much like the process of sitting in water for hundreds of years.
Nobody is twisting my arm to use it and it is more of a pain in the butt to acquire , my motives are not profit.
From Wiki for instance.....
Heat treatment can also improve the properties of the wood with respect to water: lower equilibrium moisture, less moisture deformation, and weather resistance. It is weather-resistant enough to be used, unprotected, in facades or in kitchen tables, where wetting is expected.
There are 3 similar European heat treatments: Retiwood, developed in France, Thermowood, developed in Finland by VTT, and Platowood developed in The Netherlands. These processes autoclave the treated wood, subjecting it to pressure and heat, along with nitrogen or water vapour to control drying in a staged treatment process ranging from 24 to 48 hours at temperatures of 180 to 230 °C depending on timber species. These processes increase the durability, dimensional stability and hardness of the treated wood by at least one class.
As far as complete scientific studys, there are plenty, Google is your friend !
http://www.forest.umaine.edu/facsta...ng Studies/3-2-Lianbai,Tao, Dengyun, Ning.pdf
http://www.bfafh.de/inst4/45/ppt/07_59.pdf
Here was my test.
I built a vulcanized neck 3 years ago with no truss rod.
Not once has it gone out of whack even through the Santa Ana Dry seasons, not fret sprout, still the exact same relief as it was when we made it. Then I took a cup of water and poured it on one side of a neck blank. Left it for the weekend and checked Monday, it didn't move at all. When I do this with untreated maple it will back bow. Now Roasted is half way towards vulcanized so no matter what it will be an improvement. It is not as brittle to work with as the fully bake version and has a prettier color. The major thing for me though is I love the way it sounds. It isn't about marketing because I cant get it that easily, it is about trying to offer some great product that decreases tech service calls on how to adjust the neck. It is also more dimensionally stable. I have a lifetime warranty, that is why I advise using it. In fact the next guitar I make for myself is a Roasted neck and Body.
As far as is it being snake oil? Hardly, it is only new in the use of instruments. Some acoustic makers have been treating their tops for decades.
Another benefit is weight is reduced and really opens up (my perception).
The organic sticky sap are all baked out much like the process of sitting in water for hundreds of years.
Nobody is twisting my arm to use it and it is more of a pain in the butt to acquire , my motives are not profit.
From Wiki for instance.....
Heat treatment can also improve the properties of the wood with respect to water: lower equilibrium moisture, less moisture deformation, and weather resistance. It is weather-resistant enough to be used, unprotected, in facades or in kitchen tables, where wetting is expected.
There are 3 similar European heat treatments: Retiwood, developed in France, Thermowood, developed in Finland by VTT, and Platowood developed in The Netherlands. These processes autoclave the treated wood, subjecting it to pressure and heat, along with nitrogen or water vapour to control drying in a staged treatment process ranging from 24 to 48 hours at temperatures of 180 to 230 °C depending on timber species. These processes increase the durability, dimensional stability and hardness of the treated wood by at least one class.
As far as complete scientific studys, there are plenty, Google is your friend !
http://www.forest.umaine.edu/facsta...ng Studies/3-2-Lianbai,Tao, Dengyun, Ning.pdf
http://www.bfafh.de/inst4/45/ppt/07_59.pdf
https://breedlovemusic.com/acoustic...2 ... 40ae7450ad
[IMG]
Sustainable ‘vintage’ tone and easy maintenance are affordable with the Organic Collection from Breedlove
Torrefaction. It’s a big word. If you geek out on the guitar magazines, you’ve surely come across its multiple syllables and myriad descriptions at some point along the way.
But what is it?
It’s amazing, that’s what it is.
Torrefaction makes a guitar sound aged, ‘vintage’ even, in a matter of hours, not years. What might take a lifetime now takes half an afternoon. What’s more, the procedure—sometimes called tempering, rectification or even caramelization—helps protect an instrument from the vagaries of the environment, making it easier to care for and less apt to literally change its mind like the weather.
Torrefaction is one of the key factors in Breedlove’s affordable, sustainably sourced, Designed in Bend Organic Collection of superior sounding all solid wood acoustic electric guitars. Pairing torrefied European spruce with native Oregon myrtlewood in the Artista Series and African mahogany in the Signature and Performer lines, makes for a clutch of very special six-strings that sound thirty glorious years old right now.
“Torrefaction,” says Breedlove Operations Manager Miles Benefield, “is accomplished by ‘baking’ the tops at temperatures higher than would normally be used in kiln drying the wood. Since the process is essentially aging the top wood at a much quicker rate, you get that desired “broken-in” sound, but in a brand new instrument. It definitely achieves the ‘woodiness’ associated with much older instruments.”
Torrefaction is used in other industries and is, in fact, not all that different than the technique used to make charcoal, although it’s certainly more tightly monitored for a guitar top than a backyard barbecue! The wood is ‘roasted’ under pressure in an oxygen free atmosphere, prompting, in, essentially, a wink, a profound chemical change. Lignins, sugars, pitches and other volatile elements that would either morph or outgas over decades are reduced, along with any remaining water in the wood.
“It’s much easier to maintain an instrument if its top has undergone torrefaction,” says Benefield. “Once all of the moisture has been removed, the top is much less susceptible to changes in temperature and humidity.
“This is a crucial argument for building acoustics with torrefied wood,” according to Guitar.com. “Since it’s non-hygroscopic, torrefied wood is far less likely to expand or contract, meaning guitars will be less vulnerable to atmospheric conditions and less likely to crack.”
The FSC-certified European spruce used in the Organic Collection is sustainably sourced and individually harvested in the Swiss Alps, with the thermal treatment taking place not far from where the wood is milled. European spruce is one of the world’s great topwoods, known for matching the headroom of Adirondack spruce, but offering a quicker response than Sitka, along with a skosh of cedar’s warmth. Torrefaction amplifies its best qualities, literally and figuratively, giving the pale wood an amber glow and making for a light, sensitive and agile guitar that would normally cost three to four times as much.
“The benefit is absolutely real!” beams Benefield. “Not only are you getting all the tonal and maintenance improvements, but the visual aesthetic of the rich roasted spruce is just beautiful.”
[IMG]
Sustainable ‘vintage’ tone and easy maintenance are affordable with the Organic Collection from Breedlove
Torrefaction. It’s a big word. If you geek out on the guitar magazines, you’ve surely come across its multiple syllables and myriad descriptions at some point along the way.
But what is it?
It’s amazing, that’s what it is.
Torrefaction makes a guitar sound aged, ‘vintage’ even, in a matter of hours, not years. What might take a lifetime now takes half an afternoon. What’s more, the procedure—sometimes called tempering, rectification or even caramelization—helps protect an instrument from the vagaries of the environment, making it easier to care for and less apt to literally change its mind like the weather.
Torrefaction is one of the key factors in Breedlove’s affordable, sustainably sourced, Designed in Bend Organic Collection of superior sounding all solid wood acoustic electric guitars. Pairing torrefied European spruce with native Oregon myrtlewood in the Artista Series and African mahogany in the Signature and Performer lines, makes for a clutch of very special six-strings that sound thirty glorious years old right now.
“Torrefaction,” says Breedlove Operations Manager Miles Benefield, “is accomplished by ‘baking’ the tops at temperatures higher than would normally be used in kiln drying the wood. Since the process is essentially aging the top wood at a much quicker rate, you get that desired “broken-in” sound, but in a brand new instrument. It definitely achieves the ‘woodiness’ associated with much older instruments.”
Torrefaction is used in other industries and is, in fact, not all that different than the technique used to make charcoal, although it’s certainly more tightly monitored for a guitar top than a backyard barbecue! The wood is ‘roasted’ under pressure in an oxygen free atmosphere, prompting, in, essentially, a wink, a profound chemical change. Lignins, sugars, pitches and other volatile elements that would either morph or outgas over decades are reduced, along with any remaining water in the wood.
“It’s much easier to maintain an instrument if its top has undergone torrefaction,” says Benefield. “Once all of the moisture has been removed, the top is much less susceptible to changes in temperature and humidity.
“This is a crucial argument for building acoustics with torrefied wood,” according to Guitar.com. “Since it’s non-hygroscopic, torrefied wood is far less likely to expand or contract, meaning guitars will be less vulnerable to atmospheric conditions and less likely to crack.”
The FSC-certified European spruce used in the Organic Collection is sustainably sourced and individually harvested in the Swiss Alps, with the thermal treatment taking place not far from where the wood is milled. European spruce is one of the world’s great topwoods, known for matching the headroom of Adirondack spruce, but offering a quicker response than Sitka, along with a skosh of cedar’s warmth. Torrefaction amplifies its best qualities, literally and figuratively, giving the pale wood an amber glow and making for a light, sensitive and agile guitar that would normally cost three to four times as much.
“The benefit is absolutely real!” beams Benefield. “Not only are you getting all the tonal and maintenance improvements, but the visual aesthetic of the rich roasted spruce is just beautiful.”
Before the Abstract, there was this bit from Tone Quest Report. It stands on it's own without it but:
TQR: How and when did thermo-treatment of wood begin, and who participated in the study of thermo-treated wood for musical instruments?
Thermo Treatment is a patented Finnish invention. The patents are owned by VTT Technical Research Centre of Finland, and the process has been in use since 1990 by industrial wood technologies in Finland. Thermo Treatment for musical instrument woods has been studied by Tampere Technical University in close co-operation with several musical instrument manufacturers in our country. The official research started in 1996. This study led to a 75-page report (published in 2002), which includes lots of laboratory measurements of various wood species before and after thermal treatment. We were one of those musical instrument manufacturers who participated in the study by sending wood to be treated and experimenting with the result. Each body, neck and fretboard plank we sent was measured for weight, moisture content, cell structure, stiffness, etc., before and after the process. For us, the first years were experimentation for fun, and then, even to our own surprise, we started really understanding that there is something beneficial to this process.
The co-operative parties in this study were:
Ikaalinen College of Arts and Design (Lutherie Dept.)
Suomen Ekopuu (the company responsible for the thermal treatment)
Tampere University of Technology
National Technology Agency of Finland (financier of the project, www.tekes.fi/)
Lottonen Guitars (steel-stringed acoustic guitars, archtops, www.lottonen.com/)
Taisto Pietilä (violinmaker)
Soitinrakentajat Amf (kanteles, guitars, www.soitinrakentajatamf.fi/)
Kanteleverstas Koistinen (kanteles, www.koistinenkantele.fi/)
Landola Guitars (steel-string acoustics
Ruokangas Guitars (electric guitars, www.ruokangas.com/)
Liikanen Musical Instruments (classical and flamenco guitars, www.liikanenguitars.com/)
Porthan Church Organs
Virtanen Church Organs
Each company used thermo-treated materials to build instruments that were then compared to the same kind of instruments made of non-treated materials. The manufacturers have, at the very least, compared tap tones, workability, how finishes work on the treated surfaces, weights, colors, and the tone of the finished instruments.
TQR: What did you observe in the instruments you built with thermo-treated wood in regard to appearance, the way the wood worked in the shop, and tone?
Thermo-treated wood acts differently when planed, sanded, etc. It feels very dry and the dust smells different – old and sort of “smoked.” It’s difficult to explain verbally. The wood is also tanned in color throughout. For example, maple appears yellowish/brown without any artificial coloring. Another apparent change is the bending strength (stiffness) of the wood. When we clamp two identical neck planks on the side of a table (the neck hangs out from the edge) and place weight on the tip of the plank, the wood naturally bends down a bit. Thermo treatment takes some flexibility out of the wood structure (the cell walls harden/crystallize/age) and the plank bends less than the non-treated piece. The exactly same thing occurs when wood has been air-dried for 50-100 years. Also, I think the increased stiffness improves the tonal behavior of a guitar, since it makes the neck resonate less, making dead spots less obvious or even disappear. Tonally, the differences are even more difficult to describe in detail. For example, the tap tone of a spruce top for a jazz guitar definitely changes when thermo-treated. Some of those cool lower mids jump out in a way they didn’t before the treatment. Many professional musicians have described that the guitars “sound vintage.” I know all this may sound like voodoo, but perhaps when you’ve read more about the process itself, you’ll understand that there’s a logical and acceptable explanation to these changes. Believe me, I was very skeptical, too, during the the first few years. I’m someone who wants to stand behind his words 100%.
Here is a practical example about the stability issue… A small amount of Arctic Birch was thermo-treated in 1998. From that batch, I’ve had a 6mm thick Arctic Birch flat top (cap) for an electric guitar laying around the workshop for years. It’s a bookmatched plank, sanded to thickness. So this particular piece of Arctic Birch has been on the shelf and on the worktable here and there over the years, and it has remained perfectly flat. If I had a similar piece of maple or non-treated birch, rest assured, it wouldn’t have remained flat through all the seasonal changes in Finland. I mean, even though the wood is kept in a warm place, the air humidity changes drastically indoors because of the heating here in wintertime.
TQR: Can you describe the thermo-treated procedure used for the wood in your guitars?
I can’t go into the smallest details, because even I don’t know them. The patent holder and the licensee company who treats the wood for us keep the details to themselves. One thing to point out is that the patent itself was published prior to the Tampere University study we’re describing. So, the actual patent is more general and not the exact tonewood procedure, which was developed later and is done only by one company in Finland. I’ll describe what I do know… The wood is placed in a container, which is heated, and the air moisture content is very high to prevent the wood from burning. Actually, the system might be called a kind of “steam heating” procedure. I don’t know exactly how long the tonewood is subjected to heat, but I do know that the temperature and amount of moisture change during the process is very precise. One thing that happens is that all organic “junk” in the wood vaporizes, crystallizes, or comes out of the wood pores with the heat/steam. The pattern of the process is computer controlled, parameters change from one wood species to another and by the thickness of the wood to be treated. When the wood comes out of the container it can’t be worked right away, because the moisture content is close to zero %, so it’s actually under the balanced humidity level of normal air moisture content. We have to wait 3-4 weeks until the wood reaches a more balanced humidity level. When it reaches that, the wood is very stable and good to work with.
TQR: Have you noted improved stability of thermo-treated necks?
From a builder’s point of view, the improved stability is the best feature of the whole process. Thermo-treated maple is very stable. Naturally, it still has to be straight-grained – thermo-treatment doesn’t change bad material to good! It simply is a far better method to dry wood than the conventional machine-drying. It’s so close to natural seasoning and aging that it is very difficult to notice any differences between the two, except that the color of the wood doesn’t change in naturally aged wood as it does with thermo-treatment.
TQR: What types of wood benefit most from thermo-treatment?
We have thermo-treated maple, alder, arctic birch, spruce, rosewood, ebony and spanish cedar. Maple, alder, arctic birch and spruce benefit from the treatment. The others we’ve tried – and as you see they all are more or less tropical woods (rosewood, ebony and Spanish cedar) would need to be experimented with much more before I can say anything final. So far, there have been severe problems with cracks in the tropical woods, so we don’t offer them thermo-treated at all for now.
TQR: How were direct comparisons made between wood that was naturally aged and thermo-treated?
Through microscopic cell structure study, sound velocity testing, bend-strength, absorption capacity measurements, workability tests, and experimental tap tone tests by normal spruce manufacturers (by subjective evaluation, naturally…)
One thing worth mentioning is that church organ builders have started to use thermally-treated wood in Finland during the last ten years, also for stability reasons. They have learned from experience that they have less warranty issues when the wooden constructions are made of thermo-treated wood. I don’t think they’ve thought about the tone that much – more just to pay a bit extra for the treatment to improve the general quality of their product.
Thermo-treatment was primarily developed to make wood more stable in industrial use, and it is used quite extensively by other kinds of wood industries in Finland for wood floors, solid wood furniture manufacturing, construction wood and so on. Each of these industries is very large, and they profit by the wood being more stable. They don’t have to care about the tone of wood, naturally, but these companies would never use thermo-treated wood if there wasn’t some genuine profit in it – fewer warranty issues and so on. So, there are several big thermo-treatment facilities in Finland today providing more stable wood. The tonewood treatment is just a small side path, and is done only by one company that specializes in it. And – since we’re really a tiny little country in the middle of nowhere (if I may say so), it’s only natural that most people in the USA don’t necessarily know of thermo treatment yet. Nevertheless, the benefits are real, they have been thoroughly researched and documented, and they are commonly understood and accepted here in Finland.
The following is an abstract of the full study of Thermo-treated wood submitted by Professor Pertti Nieminen, et al.
TQR: How and when did thermo-treatment of wood begin, and who participated in the study of thermo-treated wood for musical instruments?
Thermo Treatment is a patented Finnish invention. The patents are owned by VTT Technical Research Centre of Finland, and the process has been in use since 1990 by industrial wood technologies in Finland. Thermo Treatment for musical instrument woods has been studied by Tampere Technical University in close co-operation with several musical instrument manufacturers in our country. The official research started in 1996. This study led to a 75-page report (published in 2002), which includes lots of laboratory measurements of various wood species before and after thermal treatment. We were one of those musical instrument manufacturers who participated in the study by sending wood to be treated and experimenting with the result. Each body, neck and fretboard plank we sent was measured for weight, moisture content, cell structure, stiffness, etc., before and after the process. For us, the first years were experimentation for fun, and then, even to our own surprise, we started really understanding that there is something beneficial to this process.
The co-operative parties in this study were:
Ikaalinen College of Arts and Design (Lutherie Dept.)
Suomen Ekopuu (the company responsible for the thermal treatment)
Tampere University of Technology
National Technology Agency of Finland (financier of the project, www.tekes.fi/)
Lottonen Guitars (steel-stringed acoustic guitars, archtops, www.lottonen.com/)
Taisto Pietilä (violinmaker)
Soitinrakentajat Amf (kanteles, guitars, www.soitinrakentajatamf.fi/)
Kanteleverstas Koistinen (kanteles, www.koistinenkantele.fi/)
Landola Guitars (steel-string acoustics
Ruokangas Guitars (electric guitars, www.ruokangas.com/)
Liikanen Musical Instruments (classical and flamenco guitars, www.liikanenguitars.com/)
Porthan Church Organs
Virtanen Church Organs
Each company used thermo-treated materials to build instruments that were then compared to the same kind of instruments made of non-treated materials. The manufacturers have, at the very least, compared tap tones, workability, how finishes work on the treated surfaces, weights, colors, and the tone of the finished instruments.
TQR: What did you observe in the instruments you built with thermo-treated wood in regard to appearance, the way the wood worked in the shop, and tone?
Thermo-treated wood acts differently when planed, sanded, etc. It feels very dry and the dust smells different – old and sort of “smoked.” It’s difficult to explain verbally. The wood is also tanned in color throughout. For example, maple appears yellowish/brown without any artificial coloring. Another apparent change is the bending strength (stiffness) of the wood. When we clamp two identical neck planks on the side of a table (the neck hangs out from the edge) and place weight on the tip of the plank, the wood naturally bends down a bit. Thermo treatment takes some flexibility out of the wood structure (the cell walls harden/crystallize/age) and the plank bends less than the non-treated piece. The exactly same thing occurs when wood has been air-dried for 50-100 years. Also, I think the increased stiffness improves the tonal behavior of a guitar, since it makes the neck resonate less, making dead spots less obvious or even disappear. Tonally, the differences are even more difficult to describe in detail. For example, the tap tone of a spruce top for a jazz guitar definitely changes when thermo-treated. Some of those cool lower mids jump out in a way they didn’t before the treatment. Many professional musicians have described that the guitars “sound vintage.” I know all this may sound like voodoo, but perhaps when you’ve read more about the process itself, you’ll understand that there’s a logical and acceptable explanation to these changes. Believe me, I was very skeptical, too, during the the first few years. I’m someone who wants to stand behind his words 100%.
Here is a practical example about the stability issue… A small amount of Arctic Birch was thermo-treated in 1998. From that batch, I’ve had a 6mm thick Arctic Birch flat top (cap) for an electric guitar laying around the workshop for years. It’s a bookmatched plank, sanded to thickness. So this particular piece of Arctic Birch has been on the shelf and on the worktable here and there over the years, and it has remained perfectly flat. If I had a similar piece of maple or non-treated birch, rest assured, it wouldn’t have remained flat through all the seasonal changes in Finland. I mean, even though the wood is kept in a warm place, the air humidity changes drastically indoors because of the heating here in wintertime.
TQR: Can you describe the thermo-treated procedure used for the wood in your guitars?
I can’t go into the smallest details, because even I don’t know them. The patent holder and the licensee company who treats the wood for us keep the details to themselves. One thing to point out is that the patent itself was published prior to the Tampere University study we’re describing. So, the actual patent is more general and not the exact tonewood procedure, which was developed later and is done only by one company in Finland. I’ll describe what I do know… The wood is placed in a container, which is heated, and the air moisture content is very high to prevent the wood from burning. Actually, the system might be called a kind of “steam heating” procedure. I don’t know exactly how long the tonewood is subjected to heat, but I do know that the temperature and amount of moisture change during the process is very precise. One thing that happens is that all organic “junk” in the wood vaporizes, crystallizes, or comes out of the wood pores with the heat/steam. The pattern of the process is computer controlled, parameters change from one wood species to another and by the thickness of the wood to be treated. When the wood comes out of the container it can’t be worked right away, because the moisture content is close to zero %, so it’s actually under the balanced humidity level of normal air moisture content. We have to wait 3-4 weeks until the wood reaches a more balanced humidity level. When it reaches that, the wood is very stable and good to work with.
TQR: Have you noted improved stability of thermo-treated necks?
From a builder’s point of view, the improved stability is the best feature of the whole process. Thermo-treated maple is very stable. Naturally, it still has to be straight-grained – thermo-treatment doesn’t change bad material to good! It simply is a far better method to dry wood than the conventional machine-drying. It’s so close to natural seasoning and aging that it is very difficult to notice any differences between the two, except that the color of the wood doesn’t change in naturally aged wood as it does with thermo-treatment.
TQR: What types of wood benefit most from thermo-treatment?
We have thermo-treated maple, alder, arctic birch, spruce, rosewood, ebony and spanish cedar. Maple, alder, arctic birch and spruce benefit from the treatment. The others we’ve tried – and as you see they all are more or less tropical woods (rosewood, ebony and Spanish cedar) would need to be experimented with much more before I can say anything final. So far, there have been severe problems with cracks in the tropical woods, so we don’t offer them thermo-treated at all for now.
TQR: How were direct comparisons made between wood that was naturally aged and thermo-treated?
Through microscopic cell structure study, sound velocity testing, bend-strength, absorption capacity measurements, workability tests, and experimental tap tone tests by normal spruce manufacturers (by subjective evaluation, naturally…)
One thing worth mentioning is that church organ builders have started to use thermally-treated wood in Finland during the last ten years, also for stability reasons. They have learned from experience that they have less warranty issues when the wooden constructions are made of thermo-treated wood. I don’t think they’ve thought about the tone that much – more just to pay a bit extra for the treatment to improve the general quality of their product.
Thermo-treatment was primarily developed to make wood more stable in industrial use, and it is used quite extensively by other kinds of wood industries in Finland for wood floors, solid wood furniture manufacturing, construction wood and so on. Each of these industries is very large, and they profit by the wood being more stable. They don’t have to care about the tone of wood, naturally, but these companies would never use thermo-treated wood if there wasn’t some genuine profit in it – fewer warranty issues and so on. So, there are several big thermo-treatment facilities in Finland today providing more stable wood. The tonewood treatment is just a small side path, and is done only by one company that specializes in it. And – since we’re really a tiny little country in the middle of nowhere (if I may say so), it’s only natural that most people in the USA don’t necessarily know of thermo treatment yet. Nevertheless, the benefits are real, they have been thoroughly researched and documented, and they are commonly understood and accepted here in Finland.
The following is an abstract of the full study of Thermo-treated wood submitted by Professor Pertti Nieminen, et al.
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slowhand84
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- Joined: Thu May 28, 2020 2:12 pm
I would pretty much take John's position on this over anyone else's...don't know of anyone who knows their stuff in this industry quite like he does. My experience with roasted woods has all been great, even though I've experienced them on instruments of various price points. I have an Agile Epic with the roasted neck and board (and SS frets)...it's incredibly stable, feels amazing (and needs no finish), and actually smells good too which is neat. I also had a Warmoth partscaster briefly with a roasted neck, same experience...and now I have that B-Way Mercury custom guitar with a super dark roasted neck and board. This one is the best of the 3, but honestly the roasted maple made a big difference even on the Agile which was like $399 new (think I got mine for $190 or so used).golem wrote: ↑Sat May 30, 2020 8:23 pm The following is from John Suhr posting as Husky on TGP:
Here was my test.
I built a vulcanized neck 3 years ago with no truss rod.
Not once has it gone out of whack even through the Santa Ana Dry seasons, not fret sprout, still the exact same relief as it was when we made it. Then I took a cup of water and poured it on one side of a neck blank. Left it for the weekend and checked Monday, it didn't move at all. When I do this with untreated maple it will back bow. Now Roasted is half way towards vulcanized so no matter what it will be an improvement. It is not as brittle to work with as the fully bake version and has a prettier color. The major thing for me though is I love the way it sounds. It isn't about marketing because I cant get it that easily, it is about trying to offer some great product that decreases tech service calls on how to adjust the neck. It is also more dimensionally stable. I have a lifetime warranty, that is why I advise using it. In fact the next guitar I make for myself is a Roasted neck and Body.
As far as is it being snake oil? Hardly, it is only new in the use of instruments. Some acoustic makers have been treating their tops for decades.
Another benefit is weight is reduced and really opens up (my perception).
The organic sticky sap are all baked out much like the process of sitting in water for hundreds of years.
Nobody is twisting my arm to use it and it is more of a pain in the butt to acquire , my motives are not profit.
From Wiki for instance.....
Heat treatment can also improve the properties of the wood with respect to water: lower equilibrium moisture, less moisture deformation, and weather resistance. It is weather-resistant enough to be used, unprotected, in facades or in kitchen tables, where wetting is expected.
There are 3 similar European heat treatments: Retiwood, developed in France, Thermowood, developed in Finland by VTT, and Platowood developed in The Netherlands. These processes autoclave the treated wood, subjecting it to pressure and heat, along with nitrogen or water vapour to control drying in a staged treatment process ranging from 24 to 48 hours at temperatures of 180 to 230 °C depending on timber species. These processes increase the durability, dimensional stability and hardness of the treated wood by at least one class.
As far as complete scientific studys, there are plenty, Google is your friend !
http://www.forest.umaine.edu/facsta...ng Studies/3-2-Lianbai,Tao, Dengyun, Ning.pdf
http://www.bfafh.de/inst4/45/ppt/07_59.pdf
I also have a roasted aka "thermal" spruce top on my Takamine EF450C...there is definitely some truth to the tonal difference. Tak kinda describes the thermal top process as "aging" the wood, so it gives the sound of a really nicely broken in instrument in a brand new guitar. I don't know enough about the science behind that to say whether its just a marketing thing or actually legit, but the guitar sounds better than any other acoustic I've owned.
For me, I can only really judge based on my own experiences...which with roasted maple have all been entirely fantastic. I wouldn't hesitate to build a guitar with it or buy a guitar with it, and in fact am probably going for a roasted maple neck on my next Kiesel order later on this year.
I love the look, feel, and added stability of roasted maple. I don't know if it's possible to actually measure and compare whether the wood sounds like it has aged, so I avoid touting that feature. But the two roasted maple guitars I have (Sterling Music Man James Valentine and Ibanez AZ) sound different enough to make me believe that it has different tonal qualities.