Stripping a Polyester-Finished Piano Lid

      April 9, 2007

I have a customer who had a piano in storage for almost 2 years, and when they delivered to her new home the finish over the entire lid was checked. I am thinking this is due to radical expansion and contraction. The piano was moved from a home in Texas to storage in Illinois. The storage area was supposed to be climate controlled. What are your experiences with stripping polyester over a large surface? I have finished several tables in polyester, but have no experience in stripping the product. We have a flow over stripping system that we use for most of our refinishing jobs. But we may strip this lid by hand. Does anyone have any info you can pass along?

Forum Responses
(Finishing Forum)
From contributor M:
I don't personally know of anything that will strip polyester, I doubt even methylene chloride will do it. However, a belt sander will do it nicely. Particularly if you can remove the lid, belt sand off the majority, and run it through a widebelt sander (friends with big shops are great for this!) to really get to the wood unless this is veneered composite material.

From contributor H:
You might look into replacing the lid from the manufacturer. Sometimes it is the more economical thing to do. Supposedly, there is a remover that can remover poly, but I've haven't tried it.

From contributor R:
I've not seen a stripper work on polyester. Usually it's either sand it off or use a heat gun. I like the replace the lid idea if possible...

From contributor D:
I recently tried Besway P-38 on a polyester piano finish and was very pleased with the result. It actually softened the finish enough to scrape it off. I never had a remover do that before. I would suggest giving it a try.

From contributor K:
Polyester should sand off pretty well. But I would try that strip and scrape idea mentioned earlier first. I would also check into getting a replacement lid directly from the manufacturer to get the best possible match, and it may be cheaper. When Baldwin finishes their lids, they hose on the polyester. Then they pass the entire lid through a really accurate wide belt sander a few times to get it flat! It’s a pretty incredible process.

From contributor S:
Stripping polyester is similar in approach to stripping off wallpaper that is non-porous. In both cases, with polyester and with non-porous wallpaper first you have to score the surface so that your chemical stripper can get through to the substrate.

The similarities end there. With wallpaper the stripping agent will solvate the adhesive, allowing the wallpaper to let go. With polyester, the stripping agent - usually a noxious blend of methylene chloride and a strong acid - something that brings the pH of the material down to around 2 or 3, will penetrate through the film. Now that it has been scored enough to allow penetration (100 grit sandpaper) it will cause the bond of the finish to release from the substrate. It may take several applications and a lot of patience and work, but this is usually the process.

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