I've had two major experiences with this problem.  A Welte stack had
the pneumatics glued to the deck boards with PVC-E.  They were not
tightly glued, so there was quite a bit of glue.  First I tried to sand
it.  Big mistake -- big mess.  I was able to remove it by applying
semi-paste paint remover, which changed it into a gelatinous state that
easily scraped off.

A very unusual European piano, with a stack very similar to a Standard,
had the valve plates sealed by "flooding" the area all around them (the
inner chest opposite the pouches) with PVC-E.  Fortunately, the plates
had not been glued in place, but it was still very difficult to remove
them due to all of the surrounding glue.  Several bent, but I was able
to bend them back to proper shape.  The glue was then removed from the
chest by careful use of chisel and fingernails.

Craig Roothoff

Escondido, Calif.