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Wow... this conversation keeps going around the track.

Tony. I understand your confusion. I would encourage you to find the articles written about this. Many are from old GAL and Guitarmaker journals. I forget the names of the authors and the articles but I can pull them for you. That will give you a baseline to work from. The authors of these articles have explained this in a straight forward and simple way.

BUT....

you said:


"This is the question. Can heat be used to help relieve the built in stresses that might be in natural wood, by using heat – and perhaps even stickering the wood during the cooking process – to re-cast the wood into an un-natural state (if necessary) to prevent it from going “nuts” later on? In other words – using heat to bend it straight? <bg>

Simply put – could we use heat – not only to temper the wood somewhat against the adverse effects of RH and temperature changes, but also to accelerate the seasoning of the wood – making it stable by relieving the natural stresses that might be present.


quarter sawn wood shrinks evenly across all dimensions when it dries. So in a perfect world a flat plate will remain flat as it dries (and shrinks) under normal conditions. As the humidity changes it grows and shrinks uniformly in all dimensions and should remain flat. However, if the wood is heated excessivly (as in baking) the wood shrinks and does not ever quite resume the same size as it is exposed to changing RH envionrments. It is permenantly "shrunk".

Again.. I continue to reiterate... the reason for doing this is not to "dry" the wood. My wood is already suffiecntly dry to work with. The purpose of this is to shrink the wood and condition it against extremes.

Now, with the matter of stabilization. Some wood will cup and twist and bow if you don't apply constant pressure to hold it flat. This is what I am generally referring to as stablilization. I want to know if it is going to do this before I begin working with it.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I bet a good portion of Marios guitars still live in Canada. I bet he has some customers that are very happy he stabalizes his tops it is COLD up north.

_________________
"It's a Tone Faerie thing"
"Da goal is to sharpen ur wit as well as ye Sgian Dubh"
"Sippin Loch Dhu @Black lake" ,Kirby O...

I bet a good portion of Marios guitars still live in Canada

Only about 6-8% of what I've built remains in Canada.

Gets cold here in Alaska too! <bg> We're already starting to get "termination dust" out back now.   

"Again.. I continue to reiterate... the reason for doing this is not to "dry" the wood. My wood is already suffiecntly dry to work with. The purpose of this is to shrink the wood and condition it against extremes. "

Puzzled... Where do you preceive me to be in a dis-agreement with you on this? I'm certain, in my mind, this is exactly what I have also said. I'm just adding that - when you heat the wood you are removing moisture as a result - and have been asking if there are other things that we benefiting from when we do it. Where do we differ?

Brock - I'm so very sorry that my true appreciatation for you and all the other "wise" guys can't be sensed. <lame attempt at humor> You are all true gentleman, and your patience with me has been apparent.

I would still like to challenge a few points - not for the sake of argument, I'm just trying to "get there" with you. But I feel that everyone is starting to get irrated with me. So - the answer is not important enough to alienate everone.

Thanks again for trying to educate me.

I am not irritated. I understand, you have to push on it until it clicks.

However, I would encourage you to get the articles that started all of this they are very well written and make a convincing point. I will see if I can grab some authors and issue dates for you.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

First, seaoning and drying wood are two different things. You can dry wood to EMC pretty quickly, but seasoning takes time. All wood has internal stresses built in, and these are reduced over time when the wood undergoes moisture cycling. The machanism is somewhat the same as that we use in bending: the lignin is thermoplastic, which means it will 'cold creep' under a sustained stress at any level. When you bend a side you raise the lignin to it's glass point, bend the side to a new shape, and allow it to cool off to set the 'glue' again. Moisture cycling, by 'working' the wood, gives it a chance to work out those stresses. you will often see old timbers thhat have obviously changed shape since they were put in place: I've got soome kingposts in my barn that have twisted quite a lot in the 70 or so years they've been in place. So there's no subtitute for time and moisture cycling, I think.

The irreversable shrinkage thing was documented 'way back, in an article in 'Fine Woodwoorking'in the 70s, iirc. People building frame and panel furniture have problems with the panels shrinking and cracking, the same as we do. Somebody built a number of panels, put them through some extreme moisture cycling, and observed that they ended up smaller. It looks as though 'baking' wood is a way of achieving this more quickly.

The interesting question to me is whether 'baking' might, in some way, stop 'seasoning'. If, for example, the hemicellulose degradation is fixed at a certain level then you might see much less stress relief over time. This is _speculation_! It shows us how much there still is to know about a 'familar' material that people have been working for many tens of thousdands of years. Still, Mario is absolutely right; many guitar makers don't know as much as they should, and would benefit greatly from some more basic study.    

Tony,
It sounds like where you're missing part of this is this:
Seasoning involves the natural drying of the wood, i.e., the excess moisture within the cells evaporates over time, and the wood becomes dry to a certain percentage as compared to freshly cut, which is considered wet. It also gets lighter in weight due to the decreased water content, and as a result of the fibers drying. During this time, yes the wood shrinks as a result the mositure loss in the cells that contain it, and the wood may also have certain stresses locked in or dissipate as the wood dries. Obviously, the surface of the wood gets dryer more quickly than the inside, especially the thicker it is. So when guitar top woods like spruce are sliced thinner, there may be more moisture still trapped inside those inner sections which then need to dry out further, which is why we sticker tops and backs etc., to allow them to dry and shrink some more and stablize some more before we use them.
While all this is happening, there are also some changes happening to the actual pore structure or fibers of the wood, in particular, the hemicellulose. As it dries out over time and crystallizes or whatever exactly happens to it, it loses some of it's ability to absorb or release more water. It gets smaller, and the wood with it. This happens naturally over many many years, as some have pointed out. The heat-stabilizing that is being discussed here, helps push the wood to the point where it won't as readily absorb more water a little bit sooner. Therefore it is more stable, and less prone to both shrinkage and expansion in the future. In a sense, the process cuts out some of that time element to get the wood to a place where it's state is one of being more at equilibrium and stable. It's days of larger movement and reaction to changes in temperature and humidity are for the most part over.
Don't think in metalurgical terms, as a lot of that doesn't apply to the cell structure of wood...we're not re-orienting the "grain" of the wood, just shrinking and stabilizing it.
I hope that makes some sense....

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

[QUOTE=Mario] My take right now is that some folks get it, some don't. Those who don't, won't, no matter how we explain it.

That shows a lack of basic wood understanding, from a crowd I would have thought understood wood very well. May I suggest, honestly, that many of you need to put away the luthier tools and store bought jigs, and spend the enxt couple/few months studying wood, woodworking, and the old techniques of woodworking. Your instruments, and all you do going forward, will be the better.

I now believe too many here have skipped "wood 101" and went straight to "instrument making". That is like trying to grasp algebra before understand addition. Sure, we now have calculators and computers to do the bulk of the math for us, but if we can't understand the WHY, how can we understand the answer?

I state the above with all due respects, and in all honesty. Many of you need to go back to the basics.[/QUOTE]

I think everyone should read Bruce Hoadley - Undersatnding Wood. It's hard to imagine trying to build stable instruments without this knowledge. Granted you will pick up a bunch of by doing, but there is so much to know and you'll only have better knowledge from it.

_________________
Jim Watts
http://jameswattsguitars.com

Quoting Alan:
"First, seaoning and drying wood are two different things. You can dry wood to EMC pretty quickly, but seasoning takes time. All wood has internal stresses built in, and these are reduced over time when the wood undergoes moisture cycling.

Somebody built a number of panels, put them through some extreme moisture cycling, and observed that they ended up smaller. It looks as though 'baking' wood is a way of achieving this more quickly.

The interesting question to me is whether 'baking' might, in some way, stop 'seasoning'. If, for example, the hemicellulose degradation is fixed at a certain level then you might see much less stress relief over time. This is _speculation_! It shows us how much there still is to know about a 'familar' material that people have been working for many tens of thousdands of years. Still, Mario is absolutely right; many guitar makers don't know as much as they should, and would benefit greatly from some more basic study."


THANK YOU Alan!!!! This pretty much confirms what I understood to be true and was asking about – but apparently communicated very poorly in what I wrote.

“The only thing I’m seeing right now is the potential that the immediate benefits of cooking may only produce a temporary state that only time can really adequately work permanently. Good logical argument, but would that be true? Science or opinion? And if scientifically true wouldn’t time eventually catch up with the temporary fix? Or would the temporary fix prevent time from working her magic?”

Yes, I would agree with Mario and others – there is always more to learn. No will ever learn it all, however there are those who have spent a large part of their life acquiring knowledge. We would do well to seek them out and hear what they have to say.

Thanks for sharing your knowledge.

Edit identifies Alan's quote.

2nd edit: I said "This pretty much confirms what I understood to be true and was asking about – but apparently communicated very poorly in what I wrote."

NO, NO, NO, Tony. That's not what you meant to say. I meant to say "That pretty much speaks to those things I am asking about." Poor fella. Now you know why I include the quote from J. Prine at the end. A reminder to me. Hard to take back words that are easily misundersood - especially when that are wrong to begin with. Poor, poor fella.tony39001.8249884259

I'll put in another plug for Undertanding Wood by Hoadley. I fall into the category of trying to be a luthier before becoming a woodworker. The Hoadley book has been very helpful to me, and is a book I keep going back to.

_________________
David White, Toronto

"All my favourite singers can't sing."

Sounds like a good book to get. Thanks Jim and Dave.

Another good book, at least for those of us downunder is "Wood in Australia, types, properties and uses" by Keith Bootle. The first half of the book deals with wood characteristics and just about everything you never knew about wood, the second half deals with species descriptions, mostly local species but there are some common foreign species described as well. At $60 or there abouts its not a cheap book but well worth reading.

I've been following the above with a bit of humor.
There is a very easy method to describe what is happening when wood is cooked.

When studing wood tech from the National Hardwood Lumber Association the following info was disseminated in simple terms.

Wood contains two types of moisture. One is the trapped moisture that is actually in the individual cells of the wood stuctures. The other is the free or loose moisture that is wicked up into the little soda staws that are formed by wood stuctures.

Time, heat, air circulation or any combination will evaporate the free and trapped moisture down to the RH of the adjoining climate. This is dried wood.

To stabilize the wood, some or all of the trapped moisture must be removed. When moisture is removed from the cell stucture the cell collapses and remains in that shape. The more water taken out, the more tis happens, until all moisture is gone and the cell cant "shrink" any more. It is very difficult to reverse this situation. "Cooking" the wood is the easy and fast way to get to 0%.

When these cells collapse, they deform and cause the twist and warp that takes place. But, now collapsed the wood is stabilized.

When reintroduced to a "normal" RH, free water will be attracted back into the "straws" by capillary action, but not into the cell structures.

This evaporation of the cellular water will also happen to wood over an extended period of time along with the crystallization of the resins which is what "opens" up a tone wood. Cooking accomplishes most of these changes, but doesn't petrify the fibers as only time will do.

If this action of going to 0% happens to quickly, the shrinking of the cells will overcome the ability of the natural lignin "glue" to hold the cells together and the result is casehardening and honeycombing.

Onward,... when you bend sides with heat the object is to accomplish another reaction. Heat melts lignin, the "glue", in wood. To bend wood efficiently, all the cells have to be unglued, temporarly, at the same time. By heating to a given temperature for each specie and its thickness you are accomplishing this action. Cooled down, the lignin solidifies to the fibers in their new shape. This is why side bending is reversible. Just add heat.

Hope this has cleared a few cobwebbs

Dean

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Dean

well it sure has cleared up a lot of cobwebs for me,, thanks for that bit of very useful infornation... Only one cobweb left to clear up,, so you have been reading this thread for how long without offering up your knowledge.. Had fun reading the debated did you
Mike

yup!

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Dean

Thanks Dean

Mike

[QUOTE=Serge Poirier] I love Shopnotes magazine and that woodwork forum in Aussie land, great resources to the non-initiated![/QUOTE]

Hey Serge, do you frequent the ubeaut woodwork forums? That's gotta be the one it's the best woodwork forum 'round here. You should make yourself known to us, Martin and me usually kick around down there, you can find us in the musical instruments forum

Hi Paul, yes, that is where i learned how to build my drum sander, prior to finding the OLF, i learned quite a few tips on woodworking there as well and the folks there are very kind, like Aussie people always are!

I'll pay ya guys a visit from time to time!

Regards

Serge

Check out this site. Structure of wood. It doesn't answer the questions about drying or stabilization but it is interesting.

Thank you Dean. I think I understand now. You have done an excellent job of explaining the processes that I was asking about.

I know everyone else may have been trying to say the same thing - and Alan did "pretty much speak to those things" but you spoke to them very directly and painted - for me - a clear picture that answers my questions.

So, would it be correct to say: You can use cooking to imitate the natural process of seasoning through artifical cycles of heat/dry and re-introducing humidity - but the end result can not be the same as the natural process of seasoning because of how fibers becme petrified over time - and if the artifical process is done too quickly it will effect "the ability of the natural lignin "glue" to hold the cells together."

I would assume that the process of petrification would still take place over time - correct?

Thanks again.

Don - Re-read your post. Yeap. I see what you're saying now. Thanks.

Dean wrote:
<<This evaporation of the cellular water will also happen to wood over an extended period of time along with the crystallization of the resins which is what "opens" up a tone wood. Cooking accomplishes most of these changes, but doesn't petrify the fibers as only time will do. >>

I don't think anybody really knows yet what causes a tone wood to 'open up'. It certainly needs playing for this to happen, time alone simply won't do it. I've built new instruments with old wood, and they sound noow, although they do play in a bit faster than ones made from 'new' wood.

The rise in he ratio of crystaline to amopurphous material in wood with age is not solely the result of crystalization of resins: the amorphous hemicellulose breaks down and evaporates, leaving crystaline materials behind.

In short, and as usual, it's all more complicated than anny simple explanation will encompass, although the simple explanations are useful to the extent they're correct.

So what if you used a large vacuum sealer. I mean an industrial size one. I helped design a large vacuum chamber for a heating and ventilation company. They were first using it to resore old books which had water damage. This thing can realy suck out the moisture in any item. They than used it as a kind of dehumidifier to produce dried food. This worked so well that we designed a larger unit and they run both of them all the time.

Huummmmmm...... something else to think about. The "cooking" is much easier and considerably more efficient and less expensive. We all have an oven I bet.

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[QUOTE=Alan Carruth] seaoning and drying wood are two different things. You can dry wood to EMC pretty quickly, but seasoning takes time. All wood has internal stresses built in, and these are reduced over time when the wood undergoes moisture cycling. [/QUOTE]
Yep, I can testify to that. I have a couple of B & S sets that sat in the same room for about three years with no perceivable change. I had to pack them up for a move a bit after that, and, sure enough, some small splits had shown up in the ends. I hadn't sealed the ends because I thought they were "dry." I'll be sealing all new aquisitions from now on.

Alan you are correct and I was just being as simple as possible and Tony, the process is an imitation and a moderate one at that. I think to really open up a tone wood it must be flexed. That is what playing does. That is why many other luthiers subject their instruments to loud speaker music or tones. It makes the diaphram flex and the fibers slowly become more elastic, resuting in a faster response to the stimulus. High end speaker companies do this to their speaker cones before selling them to the public. The easier the diaphram flexes the more easily it will move air and it is the air preassure and frequncy hitting your ear diaphram from the guitar that causes you to hear volume and tone.

Interestingly, speakers with dense,non-reverberating, non-flexing sides and backs with coved inside corners, and isolated from other materials, and with as little connection to the speaker cone as possible are the speakers with the most pure sounds. Picture your tone wood as a speaker cone.

An accoustic guitar is really nothing more than a speaker with its own set of parameters.

Dean

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Dean