Yellow Spotted Ivory

[Patrick C. Poulson]

Good Afternoon to All!  O.K., I have a new (to me) problem that I could use
some help with.  I have a grand action from a piano that was in storage for
a while, and  some of the ivories have little yellow blisters on them.  I've
tried rubbing a few out, and have smoothed off the top of the blister, but
the yellow spotting remains.  I've seen yellowed ivory before, but not these
little yellow spots.  It looks like some tiny droplets of some kind of
liquid got on the keys, and somehow reacted with the ivory, raising the
yellow blister.  Anybody run into this before, and if so, did you find a way
to remove the spots? Thanks, Patrick Poulson, RPT