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On baking day, how may half tops do you do per bake (200degrees @ 1 hr or do you have to increase the amount of time based on the number of tops?

I can fit three in my oven. I think what matters is that the air temperature is right for all of the wood. I have a convection oven so get good air flow and a consistent temperature everywhere. Make sure you don't get the piece at the bottom blocking air flow and being significantly warmer than the piece at the top. I bake at 195 for 2.5 hours.

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David White, Toronto

"All my favourite singers can't sing."

I have a gas oven and I can fit 3 with bracewood tucked around them. I put one shelf as low as possible and use baking sheets and foil to cover areas where the heat would get through hoping it regulates it a bit evenly above. I also crack the door just a bit. I put a thermometer about halfway up and adjust the oven temp so it reads right around 200 and I usually bake for 2-3 hours. With some spruce it doesn't move at all but others, especially some of the newer growth red spruce, i find I have to sticker. Once it re-acclimates it is flat again but it will warp some out of the oven. A nice pyrex dish on top is usually enough weight to keep it okay in the oven. A convection oven is probably superior for this application. I would love to see if anyone has built a little heating box that works well too. My roomates don't always love giving up the oven for a couple of hours! They do like the smell though.

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Burton
http://www.legeytinstruments.com
Brookline, MA.

Baking the top?  Why/When do you do this?

Stefan

Stefan baking a top at say 200 F for an hour will help to solidify the resins, remove excess moisture, and at a molecular level I believe it slightly increases the density of the wood.  This may, although I have not measured it yet, have an added stiffness benefit too..  It's important to sticker the top right after backing and leave it in 45%ish RH for about two weeks prior to using it.  Of course they are baked unjoined and at a thickness that joining will not be problematic after it is baked, say .145 thickness.

The feel of the wood, if you are the sort who is into feeling your wood..... is more like fresh potato chip after backed too.

Remove all wax from all surfaces completely before baking. If there is enough surplus wood, saw off the ends past where any wax was. Otherwise, surface the wood a bit and trim all four edges a little. Once the wood exceeds the melting point of wax, the wax will flow into the wood the same as any other petroleum, and you cannot remove it. The melting point of wax is very low.

The site below has some information on supposed improvement in wood via baking.

http://www.sprucetonewood.com/dryingspruce.html

The primary reason for doing this is it shrinks the wood and when the wood reacclimates back to normal RH levels it never quite returns to size (sort of like shinking a pair of jeans in the wash and dryer).

Therefore if the guitar is exposed to extreme environmental hazards (temp/humidity) there is less of a chance of it cracking.

Bob Taylor seemed to lead the charge on making this practice popular. IIRC there are some vids of him talking about it on the Taylor web site.

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

My reading of the research actually indicates that it weakens the wood. That doesn't mean "don't do it" as the strength to weight may be increased. I'll try to dig up the paper I read on some of this.

I know its sinful, but they are so tasty when fried.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

heh, it is funny you mention this.....

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Reguards,

Ken H

You don't need an oven to bake your tops. An insulated box and a couple of light bubs will do the trick. Boyers use a hot box to cure laminated bows. This article shows you how to build one.

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Aoibeann

[QUOTE=ToddStock] Gutmeier uses a food dehydrator and isulated box...[/QUOTE]

I have never been sold on the idea of bringing the soundboard wood to 0% moisture content, as it gets in a 200 degree oven. The food dehydrator idea seems like a good, gentle way of drying the soundboard. I saw this and figured it could be modded to make it a bit longer to accomodate the length of a guitar soundboard.

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Stay with the happy people.
--Reynolds Large

I have never been sold on the idea of bringing the soundboard wood to 0% moisture content, as it gets in a 200 degree oven

Are you saying you don't like the idea of the oven, or that you don't think it will reach 0% MC in the oven?

If it's the latter, well, it's a fact. That is how we dried samples in the lab i worked in. At 212°, all moisture is driven out. we'd leave the samples in the oven a full 20 hours, though <g>

 Any lower temperature will leave some moisture in the wood. I go for around 160 myself... good enough so far.

I usually just take mine down to my local rocket propulsion lab and stick 'em in the wash... its way faster.. I mean really really faster...  All the surviving tops have proven stiffer, lighter and so far impervious to any natural or unnatural disaster they have experienced.

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Chris Oliver
Infinity Luthiers
...in the shop.

live every minute...

Torres and the the other Spanish builders of the era left their wood under shelters on the roofs of their houses. Every day the sun would bake the wood, at night it would cool bake the next day for maybe years. By the time it got to be used it sure was seasoned and ready to go.

Nothing's new in guitar building.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Honest to God....Every time I come in here I learn something new...This is new to me.....The wife is gonna flip tomorrow when I bring in a armload of tops and put them in the oven.....

Anyone ever use a microwave oven for this? Seems like there are some large enough...

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"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."

My local kiln dude told me they now have some really big microwave kilns
here in BC. He said it works really well and dries the wood from the inside
out. Works well for big stuff. Apperently the wood is less likely to check and
twist. Give it a try and see what happens!

Danny

I kept track of the first batch of 4 sitka tops I did. These were fairly new tops and had been in my shop for a few weeks.  200 degress F for 2 hours. Initially, the weight dropped 5-8% and stiffness dropped 1-3%. After a several weeks though, they came pretty much right back to where they were. One test and only 4 samples but there was a fair amount of consisteny between all 4 sets.

It seems logical that the original kiln drying process would make a difference in the results but for the wood I'm using, I'm not seeing any improved stiffness/weight ratio.

Burton, I do have a simple heating box I made for the purpose. I'll post a photo if that would be helpful.

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http://www.chassonguitars.com

--- It's not about improving/changing stiffness to weight.

--- It's not about improving/changing tone or power.

Grumpy, in case you were talking to me, I didn't say it was.  I was responding to the other posts and I only checked because of all the folks who say there is stifness/weight improvment.

I do it for the improved stability.

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http://www.chassonguitars.com

I usually just take mine down to my local rocket propulsion lab and stick 'em in the wash... its way faster.. I mean really really faster...

Chris--

Nice Mach diamonds in that motor wash.  Is that puppy throttlable?

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Jim Howell
Charlotte, NC

Here is what I have noticed in mine after baking:

The wood is much drier than it was before, so sanding it is a little more difficult due to the harder surface of the wood. Once it is sanded smooth, I dont notice the ripples of the seasonal growth rings showing up in the finish of the guitar like they do on a non-baked top.

I dont think it makes a hill of beans as far as tone is concerned.

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Reguards,

Ken H

Brock and Mario nailed it in my view.

It is not the same as kiln drying and the reasons typically used to kiln dry lumber.  In kiln drying excess moisture is removed at a far greater rate then just letting the wood season and dry over time.

We bake out tops to stabilize the wood, remove moisture, not excess moisture, AND dry up to some degree and pitch pockets.  the molecular structure is altered and as mentioned the wood is slightly condensed to no longer have the areas where the excess moisture molecules were located and these areas are condensed as a result.  When the wood acclimates to normal RH levels over time it no longer has the same degree of voids to contain moisture.

The tone benefit comes from a now more homogeneous piece of wood requiring less input to excite it.  Same for the power and projection.  The tops that I have baked go into the oven being what ever species that they are and come out feeling more like and sounding more like Adi IMHO.

The analogy might be taking a sponge and heat shrinking it.  When done it is stiffer, thinner, and will hold less moisture in the future because the voids have shrunk and these voids are where the water molecules would exist.

It is also a best practice of the major factories too from what I understand or at least Taylor.

I would not think that a microwave would work for why we do this.  Again I can see wet wood being dried in a microwave but we are not baking wet tops.  We are taking acclimated tops and further stabilizing them and baking out the pitch pockets.  Microwaves heat food by exciting the water molecules but do not heat molecules that do not contain moisture.  This of course will heat the surrounding food, wood, etc.  But it is also the reason when some things are "microwave save" they contain no moisture like plastics etc.

As for the wood being harder I have noticed this too but prefer it.  It's now more of a plate and less of a blanket.

Here is a link to Brians wood testing site.
Also we went further in testing cooked wood 1 side cooked the other left uncooked and then retesting it a year later. Its did get 21% higher Q. cooking so the pitch was set.  Also stops the pitch from eating at the finish.
mario
http://www.lessonsinlutherie.com/woodtestingandvoichirez.htm l

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