Acoustic Guitar Construction

ken cierp wrote:"Spalting is a generic term for various forms of discoloration that can occur in wood due to invasion of the wood fibers by fungal spores, which then form colonies and continue to grow in the wood. Since spalting is a form of rot, the discoloration is usually accompanied by a degradation in the strength of the wood fibers and the wood can become quite punky and eventually just rot out entirely."

I am thinking - not a good characteristic of a guitar sound-board?

Makes sense but on the flip side, if the rot continued on a finished piece of wood, wouldn't all decorative items using spalted wood eventually become punky and rot out entirely? I can see this if the wood is still part of a live tree or laying on the forest floor, but I'd have to think once it's been shaped, cut, sanded, stained, finished etc that some sort of stability ensues or else all these decorative jewelry boxes, furniture pieces, solid body guitars etc would be structurally failing. Maybe the finishing process cuts off enough oxygen to inhibit the continuation of the rot?

I think you are correct Bobby --- the drying and finishing process does halt the deterioration at some point. However, in the case of a sound board or any other structural component any visible fungi markings represent areas of potential de-lamination. For decorative purposes I know some crafts-persons saturate the spalted wood with thin CA glue to unify and stabilize it.

So if this were a spalted spruce top then it wouldn't be a good idea to use the CA to reinforce it as it would stain it green correct? Are there any other woods that using the CA to 'seal' them with that are problematic also? I see a lot of solid body guitars that use spalted lumber most often maple. Do they then seal those with CA also? Just curious and trying to expand my knowledge of woodworking in general :)

Yes if CA gets into the end grain of softwood it usually causes a florescent yellow green stain.

Keeping spalted material from fragmenting using glue is common practice --- however those application are not subject to the 125 lbs or so string tension placed on the sound board.

I have heard of cases where CA has stained other woods -- I have not had any bad experiences.

I think the naysayers are probably right but it would be interesting to measure the density and moduli of elasticity of this particular sample, to see how it compares vs. the typical range for this species. It's not hard to do and I'd be glad to help if you have it in hand or decide to buy it and find out. There is a wide variation among samples of any given species so a specimen that started out with a relatively high stiffness-to-weight ratio could, even with moderate spalting, still be above average. I suspect the damping factor might suffer from the density variations introduced by spalting and I don't know any easy way to measure that quantitatively, but at least measuring the basic properties would give you a sanity check for comparison.

I think cracks would be the issue.

I suspect the idea of 'naysayer' is something like 'You'll shoot your eye out!'. The comments about the likely unsuitability of spalted wood for a soundboard I interpret to be more like informed analysis being offered.