Sounding the Top plate of the Maple Walnut Concert guitar this week. This is one of the most interesting parts of the build. Throughout the entire process so far, from the selection of the boards to their joining, I've been sounding the wood. It's only now that I can begin to start shaping its tonal character by reducing its thickness. For this process on the back and side plates I used the drill press thickness planer, but for the top plate I used a hand plane and cabinet scrapers to arrive at the final dimensions. I find it incredibly satisfying to slice through a piece of spruce with a finely honed hand plane taking paper thin ribbons of wood. The drill press plane is efficient but can be destructive to the softer spruce, especially around the edges which can tear out along the grain lines if I'm not careful. The hand tools are much easier to control and I'm able to shape the top by feathering it down to the edges which are left thinner than the central belly making the plate as responsive as possible.
I have some general numbers in mind when I start, but I'm not a slave to the gauge. Each piece of wood is different and will open up at different thicknesses. By open up I mean there's a point when the tone that the plate is producing when sounded by tap testing goes from sounding stiff and controlled to loose and resonant. It's difficult to describe. The sound just "opens up." That's what I'm looking for. The plate will also become noticeably more pliable. Care must be exercised at this point as too much pliability could lead to structural failure. That's always the battle when building a stringed instrument: to let it resonate as much as possible without it vibrating itself apart. It's a balance I think I've found with this top plate. Time will tell.