Humidity and tonewoods

[whvick]

Short of going to carbon fiber, are some tonewoods less susceptible to humidity than others.

[iim7V7IM7]

Originally Posted by whvick

Short of going to carbon fiber, are some tonewoods less susceptible to humidity than others.

All koa guitar....

[The Bard Rocks]

I'd first look to Port Orford cedar. Actually a cypress, it is usually used as tops but once in a great while B&S. There are probably others as well.

[charles Tauber]

There are woods that expand and contract in size less than others for the same change in humidity. For most woods, quarter sawn orientation expands and contracts less (across their width, which is what matters most) than flat/slab cut wood of the same species. Thus, you'd want quarter sawn woods of species that "move" less.

However, construction details can also make a big difference, with some implementations being much more sensitive to humidity changes than others. Torrefaction reduces, but does not eliminate, the sensitivity of wood to humidity.

Regardless, solid wood instruments require a certain amount of care, regardless of how the wood is cut or what species are used. There is no getting around that: if it's wood it's going to require at least some attention to humidity levels.

[Simon Fay]

You can go to laminates -- but you're generally dealing with lesser instruments. For solid wood guitars, it's hard to beat a sitka/mahogany guitar for durability as both wood species are exceptionally stable.

[RalphH]

Given Koa is suppose to be pretty good with humidity changes, as are laminates, I figure my solid top, laminate b&s all koa taylor gs mini is about as humidity stable as a solid-top guitar can be, which is pretty convenient given it's a travel guitar.

If you want full-size then the 224ce-K is a solid top, laminate b&s all koa guitar too.

[s2y]

Ebony is very sensitive. Take charge of your humidity.

[agfsteve]

Interesting thread, and I hope I'm not hijacking it with these wonderings?:

Might a guitar whose whole body (top, back, and sides) are all made of the same, all-solid, wood fare better, on the assumption that the entire body will expand and contract as one? Woods that I'm aware of that could be used for this are mahogany / sapele, koa, maple, and myrtlewood... any others?

On the other hand, might a guitar whose back and sides are laminated fare better, on the assumption that they will provide better support for the top, in that they won't expand and contract, thereby holding the top in place better? And of course, the back and sides themselves will at least be resistant to humidity changes.

The two postulations above are basically opposites, so does anyone have an opinion on which one might have more validity?

...aaaand I just now realised that I forgot about bracing, so that might throw off the "everything-is-the-same-wood" theory. So on that subject, presumably heavier bracing makes the top less vulnerable to humidity changes? Does any builder use non-wood bracing?

Also, does anyone know of a guitar maker who claims that their guitars are better at handling humidity changes than other makers? I don't recall ever seeing any claims like that, which is understandable. Breedlove does actually make some claims about their bridge truss system making the top more stable, but I'm sure they advocate maintaining optimal humidity, just like other makers.

[charles Tauber]

Originally Posted by agfsteve

Might a guitar whose whole body (top, back, and sides) are all made of the same, all-solid, wood fare better, on the assumption that the entire body will expand and contract as one?

It isn't as simple as that.

Wood is an "anisotropic" material, meaning it has different properties in different directions. One of those properties is the amount by which it expands and contracts in response to environmental humidity. To deal with that, fine woodworkers generally follow certain rules in the design and construction of what they make.

One of those rules is that wood movement cannot be stopped and one should not attach/glue pieces of wood together that attempt to impede or counter the movement of one piece relative to another. Guitar makers violate that rule all of the time. Gluing a long-grain brace across the width of a guitar top, back or sides are example of that. Gluing wide, thin pieces of wood to a rigid frame, such as the top or back to the sides are examples of that.

In short, guitars are typically constructed using orientation of wood that wants to move in different directions. The structure of the guitar attempts to impede that movement. The materials don't try to move as a unit all in the same direction.