Luthiers prize koa wood for making fine instruments.
Koa is a native Hawaiian wood known for its attractive color variations and beautiful sheen when finished. Grains in koa wood vary widely, with designs such as fiddleback, plain and curly. These factors make koa popular for furniture as well as musical instruments and weapons. Koa can be tricky to finish without damaging the wood. There are a few tricks for sanding koa that may help when finishing the wood.
Use Sharp Tools
When preparing koa wood for sanding, make the job easier by using extra sharp tools. Koa wood is high in tannins, which create black marks, sometimes called burns, on the surface of the wood. Dull tools increase the release of tannins. Tannic stains are difficult to remove with sanding, so avoid releasing them by using sharp tools.
Clean Sandpaper
Sandpaper should be clean, with sharp grit to avoid the same tannic staining. Use fresh sandpaper, and change it frequently.
Sand Instead of Planing
Although koa wood does plane easily, with curly grain koa, planing can cause tearout. If it is necessary to reduce the thickness of a curly grain koa board, sand instead of plane when possible.
Aggressive Setting
Using new sandpaper with sharp grit, electric rotary sanders should be set on "aggressive" setting for the first smoothing of a rough-sawn board. This will level out the cross hatching that often occurs in koa when it is rough-sawn. Once the original board is leveled, switch to a less aggressive mode and use increasingly finer sandpaper grits.
Vacuum
When sanding koa, it is helpful to have an electric sander with a vacuum hose that collects dust as it sands. This keeps the sandpaper clean so it can be changed less often and the sanding is more effective.
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