Finishing over Polyester

A fully cured polyester base coat accepts several kinds of topcoats. Scuff first. March 9, 2006

Has anyone successfully finished over a polyester finish and if so, what were the procedures?

Forum Responses
(Finishing Forum)
Piano refinishers do it all the time. Scuff first. Also, many pianos have a polyester primer/sealer over which is coated with a lacquer topcoat. There is a school of thought that some polyesters off-gas continually and that this off-gassing could interfere with the topcoat. However, as I said, piano refinishers do lacquer recoating frequently.

The big unanswered question is how durable their lacquer topcoat is sitting atop polyester, versus the Yamaha pianos which come out of the factory with polyester basecoats and lacquer topcoats. Do some polyesters, which are meant as topcoats (and then they become undercoats), interfere with the normal scratch resistance of a new lacquer topcoat because of that off-gassing? Those are the issues I know of.

From Bob Niemeyer, forum technical advisor:
Most PE finishes can be over coated with almost anything from NC to CV and also PU. But if you are mixing brands, please do a test on a small part before doing the complete job. PE is very inert when cured. A very good sanding with a grit of 220 is a must before topcoating.