Piano: 10-year old Schimmel walnut grand with high polish polyester finish. Overall finish is still in near-perfect condition.

Problem: Just 3 week's worth of exposure to sun after being moved next to picture window has caused slight cloudy/hazy look to sun-exposed section of the finish on that side. Red-brown stain color does not appear to have started bleaching out, yet, but the surface of the finish looks cloudy and white-ish.

Customer was planning to purchase window coverings and thought she had at least a few months of sun exposure (at only 3 hours a day) before any haze or color deterioration started to appear. She has now rushed to cover windows/piano to prevent any further effect, but is asking if there is way, short of stripping that section down to bare would and rebuilding-up finish ($$$) , to restore original clarity of the polyester.

Your suggestions please...thanks

I don't know of anything that could repair UV faded stain. If the cloudiness is at the surface of the clear coat maybe sanding and buffing the polyester top coat would improve it.

I look forward to other peoples suggestions who have more finishing expertise than me.

www.ProfessionalRefinisher.com It's an Elitist organization but you may be able to get into the forums as a guest.

If you want to know about finishes or wood / repair in general that is the place to go. There are a few of us piano restoration folks on there too including one out of Los Angeles that specializes in Polyester.

There are products for cellulose based lacquers, they are well known for clouds.
On polyester, dont know, I woukd ask Schimmel first, then the poly provider. Could be BASF, or Koenig, certainly others...(Germany)

With clear coats there is no way to tell how deep the damage goes.

UV damages furniture finishes along with colour barriers even in cloudy periods or when not in direct sunlight.

Hard sanding and re-coat, then polish out. Have your wallet ready.

The ozone hole was not so large when those products where made, while they inclued some anti UV treatment it can be not enough.

the anti UV only in the clear coat for what I understand. Under coat can be PU, not polyester, while I dont know how much incidence it may have.

With time, not only the polish but the wood color fade, and then rosewood looks like walnut.

Don't limit yourself to just piano technicians/restorers. Seek out high quality furniture finishers. After all, the question is not about a piano, per se, it is about cabinetry and the care/restoration of a given type of finish.

Thanks, I emailed Dave at www.ProfessionalRefinisher.com, we'll see if he responds to a non-member like me

Is the "(member) out of Los Angeles that specializes in Polyester" Greg Wood at Polytek? If so, he is already a colleague of mine, through Keyboard Concepts, and I've already put out a word to him. He may actually be the best guy for me to discuss this with, hope he responds soon.

I've had this happen on one of my customers' piano. It seemed to be just on the surface so I put the buffer to it and it came right out. This was on a Kawai product. No telling with Schimmel.

Good to know, thank you for the witnessing.

buffering produce heat, may be it cure the cloud by allowing the product to reactivate (or do you believe this was really a so thin layer it could be taken out by polishing ?

It was definitely just a thin layer.

Polyester does not "reactivate" like lacquer does. It can take quite a bit of buffing heat. However, not all pianos are finished with polyester and not all parts of the same piano are necessarily polyester.

On the Schimmel, I would pick an out of the way spot and try a little hand polishing with some fine compound.

Only certain lacquers can be restarted.

I was told to warm a little the poly so the polishing is easier, and it is less hard in that case (some poly anyway)

but I may admit I never allow the warmness to raise much

About ten years ago the German manufacturers all had a problem with cloudy finishes from the same finish supplier. This may have just not been noticed until it got put into the sun. If this is the issue, buffing is not helpful. The manufacturer that I worked for replaced the pianos that had this problem.

Is this really a UV problem?? I would guess not, since glass blocks 99% of UV.

It seem to be little more complicated than that, with different kind of UV :

http://www.newton.dep.anl.gov/askasci/chem00/chem00539.htm

Could you be more precise please (supplier for instance) PM me if you wish.

This is a problem with Internet information, cannot be checked easily because it is often vague.
I just had the same with a water heater that stopped functionning, and someone on a forum wrote that the problem on that model (an electrical relay that broken without reason) was well known by the brand ;
I thought I was on something and that I could have the guarantee involved, but I discovered that the information was in the end nothing because not precise enough (it always can be done by PM if one does not want to post publicly about a brand)

That said, thank you for posting, and the cloud problem you talk of can be indeed real at some point in time of course.
(I did not heard about but this is comprehensive)

I think it was BASF. The cloudy spots were not really evident unless it was in sunlight or very bright light. It looks like a bloom in a lacquer finish and could not be polished out.

Thank you ... then it was not due to the sun but to the bright lightening