Jim Wilson wrote:

Tom Watson wrote...

I wonder if there is any kind of treatment that would render the
pieces more resistant to this kind of damage without substantially
altering the look.

Not that I know of. Ebony is so dense that liquids don't penetrate into
it very well. I should temper that a bit; I've only worked with Gaboon
ebony, but the ebony chess sets I've played seemed very much the same.

Out of curiosity, why not place lead shot or strips in the bottom of the
chessmen and then fill the rest of the cavity with epoxy? No charred
wood or concern over density etc.