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I recently learned there are builders that "cook" the spruce top pieces. Can anyone share any information? Recipes? Thanks, Rob

Here's some info from past OLF threads.



http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26711&p=359182&hilit=cooking+spruce+tops#p359182

http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=22709&p=311847&hilit=cooking+spruce+tops#p311847



David Wren http://www.wrenguitarworks.com

I tried it with a few tops last year and really couldn't hear any difference. There substitute for playing it in IMO.

While I will heat a top , I do that during summer . The reason is more to just help get moisture out . You cannot run the moisture to 0 as that is impossible and still have a usable piece . I do it to get excess moisture out . In my early days I believed that you could heat and cure the resins . I do not think that is true , time does that . Heat will help when RH is high to bring the moisture content down so you can create a more stable top in RH changes.
Gluing up a top in summer or high RH times can make a top a prime candidate to move and shrink to the point of cracking in sever dry times . I use a heating blanket set for 250 for 10 minutes . I don't bother using it in the winter . Only when the outside RH is about 60%. Then I glue braces on it right away .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Haans,

It was my understanding that baking tops is more about stabilization of the wood rather than enhancement of tone.

I believe the idea is that 'after' the drying process has been complete, spruce is baked in order to raise the temperature of the wood so 'volatiles' within the saps expand and exhaust themselves from within.

Certainly if this is the case what remains of those saps must be more crystalline. But the whole point of the exercise as far as I am aware is that the wood itself is left in a state whereby it no longer able to expand and contract to the same degree it once did. Maybe this also has some positive affect on tonal outcomes, but if so, it is secondary to the reason I have been told that Taylor Guitars have adopted the process. As I understanding 'their' chief concern is to lessen the negative impact on their instruments when they are exposed to a catastrophic heat event such as being left in a locked vehicle on a hot day....important stuff when your trying to establish a brand as the most consistent and 'reliable' factory built guitar.

Cheers

Kim

Ahh, I see. I guess 44% RH would take care of that problem.
Don't think anyone with half a brain would leave their instrument in the car on a hot day, though.
So, are Taylors consistent and reliable? Scratch that, don't much care...

So are you suggesting that you need more than half a brain to buy a Taylor?

I would suggest that its all about percentages Haans, if they find that they are getting 50% less guitars back for repair from 1/4 brainers, then the exercise is validated.

Oh and like I said, it aint about 'moisture' nothing to do with it whatsoever

Cheers

Kim

I definitely hear a more reactive tone following baking. What I have also consistently measured is the 7% permanent weight reduction following the bake cycle up to a year later so far. I still believe that the low MW resins are driven off as gasses while the higher MW crystallized deposits on the surface (easily sanded off) form during the process. The sound difference is noticeable after the guitar is completed...

I also believe you can get the same effect from playing in...over 5-10 years!

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JJ
Napa, CA
http://www.DonohueGuitars.com

Nope, just suggesting that anyone with half a brain would not leave the instrument in a car.
As far as cooking, just stating my experience. Of course most all my tops are 15 -20 years (at least) old anyway...maybe they are already "cooked". There was no resin powder or crystalline leakage after a week at 150 degrees. Not much weight difference after re-acclimation to my shop RH.
Most of the tonal breakin that I hear on my instruments occurs in the first 6-8 months. After that it is the law of diminishing returns.
Anyway, my opinion, my experience...

Rob, I like to cook my spruce tops at 200 degrees farenheit for one hour. I have seen resins deposit on the surface that are easily sanded off. If you decide to go this route, make a jig, or sticker and put weight on the plates so as to keep them flat.

Chuck

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From my experience, if the wood is dry to begin with, baking leads to no noticeable improvement in stiffness/weight ratio once the piece has reached EMC again.

It's my understanding that baking breaks down the hydroxyls in the hemicellulose causing the wood to be less hygroscopic from there on out.

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http://www.chassonguitars.com

How different is this process than the normal practice of setting pitch on Sprice/Pine/Fir lumber during kiln drying? Temperatures used during that schedule are slightly lower (~160-170 dry bulb) and the wood is much thicker. Is 200 degrees required or is there something else happening to the wood at the higher temps? Knowing that most kitchen ovens don't regulate very well I'm afraid to overshoot and burn up my tops.

Sticker after baking or during baking?

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Formerly known as Adaboy.......

I will admit that I can't hear any difference but I have 30 plus years in production but I do see a more stable top . None of my tops have cracked since doing this . To be fair , I also control RH a lot better than the early days . I do feel that the heat lowers the MC so that will aid the stability for sure during low RH where cracking will most likely occur .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Hi all,

Great topic (although it is not a new one, as it as been mentioned).

I know we are talking about spruce but as anyone tried it with cedar?

And most of you seem to have tried it on steel strings, but as anyone tried it on a classical or flamenco? I'm asking because I've noticed that the lower string tension of nylon strings tend to make guitars that are more sensible to differences in wood properties than with steel strings. For exemple, a 7% difference in the weight of a top is something that will be less noticeable on a steel string than on a classical.

One thing I know, I'm definitely going to run some tests shortly!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Everything Taylor uses is kiln dried so they apparently believe there is a difference between baking and kiln drying.

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http://www.chassonguitars.com

I recently took a stab at baking some tops. One hour at 220 yielded a 20g reduction in weight and around 10-12% increase is stiffness along the grain. Tap tone, well I couldn't quantifiably say. Unfortunately I didn't sticker them afterwards and a few days later they warped all over the place. Anyone know how to reflatten a warped top panel?

Darryl, I sticker mine in a jig during the cooking and after with weights until the tops acclimate to my shop humidity, The reason I use a jig is that it takes less room than weights. The jig is simply two sets of thin metal pipes (cut up closet rods) drilled out on the ends with allthreads to bolt the pipes together. Works great and no staining.

Chuck

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Well, of course not. It's people with a whole brain that do this.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.