refinishing problem

[jim krentzel]

List,
I've refinished pianos for over 15 years, but a grand that I'm working on
now has me stumped.  The entire piano has refinished just fine with the
exception of the large lid.  After the second series of sealer coats, the
finish develops small bubbles.  The bubbles feel like bumps about the size
of a pin head, but after wet-sanding, they are small craters, so I know they
were actually bubbles in the finish.  After the first time this happened, I
stripped the lid again and started over.  I had the normal amount of
fish-eye on the lid, but it went away after the first 4 coats of sealer
(with fish-eye eliminator) were wet-sanded flat.  Then after the 4th added
sealer coat, the bubbles appeared.  I'd appreciate any suggestions.
Jim Krentzel