[pianotech] Plate finish problems

[Ron Overs]

Hello Dale and all,

You've had a lot of good advice from others.

We finish our plates with automotive finishes, either acrylic lacquer 
with single pack primers, for the budget jobs, or 2K two pack with 
polyurethane 2 pack high build undercoat, for the serious work.

When a plate has been refinished previously, without proper 
preparation, like the plate image that Ron N was unfortunate enough 
to encounter, I believe the only way to guarantee a good outcome is 
to sandblast everything off. But this will remove all of the original 
factory filling as well, so you'll need to start from scratch. A good 
high-build undercoat is very useful, but it is not a good idea to use 
it for all your filling. If the undercoat film is too thick it can 
lead to problems later on. Our approach is to use car body filler on 
the seriously dimpled and badly shaped plate areas to get the larger 
imperfections sorted, sanding them to shape with very coarse paper 
(80 grit),  The preparation is quite quick, and very much reduces the 
thickness of primer filler which will be required to achieve a 
quality and well profiled base for applying the colour and clear 
coats. We use a polyurethane two pack undercoat for our 
remanufactured and our new pianos, which is easy to sand, high build, 
and it stands up better under the 2K paints (we add the gold powder 
to 2K clear for applying the base colour) when compared to single 
pack acrylic lacquer all purpose primers. We use the same method with 
our new pianos also. We buy our polyurethane undercoat as a white, 
which the manufacturer tints to a biscuit yellow for us. We find this 
gives a better base for covering with the gold powder. With grey 
primer there is a risk of getting a result which looks great when 
you've first applied the gold powder coat, but sometimes the grey can 
show through once the clear coat is applied, where the colour 
application has been a little thinner. The biscuit primer gives a 
much improved result. Many of the OEM 2K primers are already supplied 
with a biscuit colour, but they are expensive. We are getting a 
similar result at less cost with the polyurethane.

Please don't use two packs for finishing unless you have a properly 
ventilated area. When I was in my twenties, had black hair, and used 
2 packs without proper ventilation on pianos, I got grey hair. When I 
stopped filling my lungs with isocyanate, the greyness went away. Its 
back again today, but that's another story.

Regards,
Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
_______________________
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://ptg.org/pipermail/pianotech.php/attachments/20101121/ec9cdb50/attachment.htm>