Finish Over Polyester?

[gordon stelter]

Wet sand with naptha instead of water, and you should
have no problem with core wood swelling.
     Thump


--- Overs Pianos <sec@overspianos.com.au> wrote:

> Hello Philip,
> 
> At 12:24 PM -0400 25/10/04, Philip Jamison wrote:
> >
> 
> >I have a nice black lacquer Yamaha grand with a
> white
> >polyester music desk! Obviously a replacement, I
> wonder if I
> >can safely apply black lacquer over the polyester.
> 
> You certainly can. Repair any cracks or damage in
> the polyester 
> first, then cut it back to 600 grade (wet is better,
> but don't get 
> water in the screw holes or you'll ruin the flatness
> of the finished 
> job, then light dry sand before applying the top
> coat). Never apply 
> lacquer to a wet sanded substrate or you may get
> keying (adhesion) 
> problems. If you cut it by hand using a cork block,
> make sure you 
> sand the bottom surface of the block flat on a known
> flat surface 
> (eg. the cast iron bed of one of your workshop
> machines). If the 
> cutting block isn't flat you will not get the panel
> flat. I give my 
> cork blocks a wipe with 150 grit paper on a flat
> surface every time I 
> use them because the water from the previous use
> will cause the cork 
> to swell and distort. The same applies to wooden
> blocks if you use 
> them. Wooden or hard synthetic blocks are a must
> when repairing 
> polyester damage - or the result won't be flat.
> 
> Lay up two or three medium-wet coats of lacquer,
> block sand to 1200 
> wet (or 2000 if you have it), then buff and final
> polish with a foam 
> pad at low speed (I use a speed control on a Makita
> polisher, with a 
> custom handle made to lower the handle-height down
> to about 50 mm 
> (2") higher than the pad surface for better
> control). As with 
> buffing, always polish with the foam 'rubbing' from
> the flat area to 
> the edges, and definitely not the other way round or
> you'll burn the 
> edge. Lacquer won't be as hard as polyester but the
> finish standard 
> can be every bit as good.
> 
> Yamaha use lacquer for some of their parts and
> polyester for others 
> anyway (in the same piano). Make sure you are using
> a proper 
> 'jet-black' black, or your repair area will look
> smokey-grey against 
> the original panels. A lot of the new automotive
> finishes use the 
> proper black color. The current Mazda jet black is a
> perfect match 
> for Yamaha. Furthermore, you can get it in a two
> pack material (if 
> you have the proper respiration gear to avoid
> premature greyness from 
> the cyanide content - not to mention an early death
> should you make a 
> thorough job of inhalation). The two pack material
> would be much more 
> durable for the music stand.
> 
> Ron O.
> 
> -- 
> OVERS PIANOS - SYDNEY
>     Grand Piano Manufacturers
> _______________________
> 
> Web http://overspianos.com.au
> mailto:info@overspianos.com.au
> _______________________



		
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