Dear Brian, You were correct - the furniture polish has left a coating on the piano, and the Cory polish reacted with it. The black color is puzzling - but that could just have been from the polish and dirt. The piano is polyester with a tip coat of (most likely) polyurethane varnish. The Cory polish shouldn't bother the varnish at all. >From the customer's point of view, he is happy with the results of the polish he is using, so there's nothing really wrong with it - as long as no one tries to use regular cleaning things on it. Simple water will make the wax build up look bad also. Don Mannino RPT
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