Bruce Clark suggested using Elmer's glue rather than varnish with piano
decals.  I'm not sure that this is a good idea, as white glues, like
Elmer's glue, turn yellow over time.  Decoupage material, such as Modge
Podge, is used by artists because it does not yellow, but I don't know
if it has the longevity that would be expected of an adhesive used for
a piano decal.

Meta Brown