[pianotech] Polyester Repair problem

[pmc033 at earthlink.net]

Hi, Chuck:
    Unless you are lucky, going further is probably not going to make things better.  Using a different type of material and attempting to blend the area won't work, as a high gloss cannot be achieved to match the poly.  If the area is small, like the size of your little fingernail, you may be able to fake something.  But, if you attempt to fill the larger bare/grey area with polyester, when you go to level it, you'll only reveal more undercoat and make the problem worse.   If there is someone in your area that refinishes in poly, you could sub it out.  
    It is possible that the original finish was a very thin urethane instead of poly, and thus you sanded the finish off, not recognizing the "imposter".  Yamaha finishes are extremely thin, even in polyester, and sanding through is easy to do and not easily repaired.  Not only that, Yamaha poly is very hard.  That makes it more likely that the new repair material will be worn away as you buff, leaving a divot.   
    I wish I could tell you how to spray polyester, but I have never attempted it.  I know two shops locally that do that, so if you are stuck and want to go in this direction, I could send you to the right people.  
    Quoting an ex-president, "I feel your pain".
    Paul McCloud

----- Original Message ----- 
From: Chuck Behm 
To: pianotech at ptg.org
Sent: 04/23/2009 8:42:16 PM 
Subject: [pianotech] Polyester Repair problem


Dear List - In repairing a chip on the front of a Yamaha fallboard using the Schaff polyester repair kit, I got too ambitious with the 500 grit wet/dry paper during the leveling out step and rubbed through the black in a spot next to the fill. Since I'm only at 500 grit, I'm sure the problem will worsen as I go through the rest of the grits. When I realized what had happened, I decided I needed to stop right there until I was sure of what steps I should be taking next.
I'm clearly out of my element here, and need advise. Do I need to spray over  the entire front of the fallboard, or just the side on which the repair is located and feather it out,  or is a simple touching up of the rub-through possible? What product or product and techniques would work the best? I have a good compressor and spray equipment, if that would be needed. My only concern is that the completed job looks right when it's done.
 Rarely does anything less than 75 years old come into our shop, so working with hi-gloss ebony is something I hardly ever do. Words of wisdom from someone in the know would be highly appreciated.   Thanks in advance, Chuck
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