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Bowing sitka top

Total Topics: 9
Total Posts: 17
My OOO Sitka top seems to keep an inward bow after a recent repair of a crack from a falling tool on my work bench. I can relieve the bow using an iron on medium heat with no steam. After a few minuites the top lays down. but it has bowd back after a few days. My work area kept a RH of about 50% @60 degrees. I am at the point where I need to put the top braces on. My question is should I use the iron technique again and brace the top after it is flat again or do some thing else?


Feb 06, 08 | 9:28 am

Total Topics: 34
Total Posts: 567
It sure sounds like a humidity issue to me. For what it is worth, after thickness sanding I see my tops bow and curl all the time before bracing with humidity swings as little as 5%. These very thin pieces of wood are quite sensitive to even the slightest humidity change, and it happens fast. I wouldn't iron it as you risk weakening the center glue joint, or repair glue spots. I would try to keep it in a space (plastic bag) when not being worked on that will help with any humidity swings. When I get to the point that I am close to bracing, I store my tops in a bag for about a week before I do the gluing. That helps stabilize the wood moisture level. Until then, I just set it in my shop and try to keep the shop relatively stable (which is very hard with a 100+ year old un-heated barn workshop!). I set them on stickers with a flat piece of MDF on it to help weight it flat.

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Feb 06, 08 | 9:55 am

Total Topics: 9
Total Posts: 17
thanks for the info, i thought it was probably a humidity issue, I will keep the iron away from it and put it in the plastic bag as you suggested. if i understand you correctly this is common and the bow will correct itself after the bracings are glued correct?


Feb 06, 08 | 10:27 am
Ken Cierp

Total Topics: 58
Total Posts: 2262
Hi Richard,

Here is something I would try (beside getting the humidity down) let the top sit face down over night and see which way the top curls. The next day let it sit with the face up. In both cases the it should bow "up" because more ambient mosture can get at the upside. If on the other hand it has a tendency to bow toward the face either night I would not be too concerned. But if the bow is away from the face and result in a concave top ---- I personally would be leary of using it.

Also I don't believe in using heat or mosture to flatten material, to me that only creates a false enviroment, and I am not sure what the point would be??
The top stays flat a little while after heat is applied -- so ??
Two Cents


Feb 06, 08 | 12:17 pm
blues creek guitars Authorized Martin Repair Ctr

Total Topics: 52
Total Posts: 1011
The wood cells will pick up moisture and as they expand you will see this happen. There are some builders that do "roast" their plates before gluing. I feel once the wood has been seasoned and cured the heat thing isn't doing you any benefit.
Let your wood acclimate and do this with the wood so air can get on both sides. Wood laying flat on a bench will always let the air side acclimate faster than the hidden side. Try setting this on a few slats and weighted down for a few days.
I do not let any unbraced wood set in open air unless it is pressed. Ken and I are in total agreement on this issue for sure.
john hall
Blues Creek Guitars

Feb 07, 08 | 5:45 pm

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