When trees grow in certain soil conditions, mineral deposits will sometimes form in the wood. The minerals come in with the tree’s water up through the roots and collect into isolated areas. They are usually seen as minute, very hard, crystalline lines that form along the grain line. Unfortunately, they are very light in color and can be a demanding blemish, especially on darker woods! But there is no need to discard good wood with mineral deposits, you just have to know how to deal with it.
Mineral deposits can be found in many different species of wood. We see it in Ebony, Rosewood, Ovangkol – even our domestic Redwood. When it appears in a hardwood like Indian Rosewood the best way to remove it is to simply take some time to physically pick it out. Your tools are a sewing needle and a good pair of magnifying glasses. Sometimes a scalpel or Exact-o- knife is used. It won’t take long to work over a set of back and sides, and if you are careful, you will remove only a tiny amount of wood fiber. Of course, this is not an option for some types of deposits and is not feasible in a fast-paced production environment.
Many builders report that mineral deposits will ‘disappear’ under a sealer coat of shellac, like the dewaxed flake shellac we sell for French Polish. This is always worth trying so long as the shellac doesn’t interfere with your finishing scheme, but results are not 100% guaranteed. And of course, on instruments where a dark paste wood filler is used, the mineral will be concealed beneath it, provided that all the mineral resides in a recessed area (which it normally does).
Indian Ebony is a rarer case. The mineral there is not seen as white lines, but more as cloudy patches. The wood is non-porous and there are no distinct grain lines from which to pick the mineral out! This wood is primarily used for fingerboards, and it’s a blessing to know that this sort of mineral deposit disappears when any standard fingerboard oil is applied. We found our FFOA oil to be the most effective.