David, bone black is often used to highlight certain areas of a stock--places where a dark area are wanted. I've used it on carved flintlock rifle stocks, dusting it into wet finish around carving, etc. If gives those areas a very pleasing contrast. I can't think of any practical use for it on doubles unless you're restoring a piece and want the wood to have an aged appearance. Maybe SDH will chime in here--he certainly has the experience. I'm just a duffer. A good substitute for bone black is ground up artist's charcoal. Has basically the same effect.
