Polyester Repair

[Stan Kroeker]

>> Date:          Sun, 10 Aug 1997 13:23:08 -0500
>> To:            pianotech@ptg.org
>> From:          skroeker@MTS.NET (Stan Kroeker)
>> Subject:       Re: Polyester Repair
>> Reply-to:      pianotech@ptg.org
>
>Stan,
>
>I would like some advice on buffing out polyester pianos.  What
>kind of buffer is the best.  Polishes?  What to look out
>for when attempting this work.  I have many pianos that could
>really benefit from this work and I would like to be able to
>offer the service.  Many years ago I help prep pianos for a
>dealer at a "warehouse".  They had a great touchup man who used
>this hand-held electric buffer.  I believe he squirted on some
>kind of a polish as he buffed the finish.
>
>Thanks in advance...
>
>David ilvedson, RPT
>Pacifica, CA

David,

I own a Black & Decker (industrial grade) 'Buffmaster' electronic polisher.
Although the Milwaukee mentioned in another post is a high quality machine
as is the Makita, they are quite a bit more costly than the B & D.  Look
for a machine with variable speed (mine is 0 - 3000 rpm).  I think they all
have trigger locks which make for less discomfort during long buffing
sessions.

Another post mentioned the foam pads which attach to the buffing adapter
with velcro (I think 3M makes these 'Hook-It' pads).  Although I have not
used these, I have heard encouraging opinions.  My understanding is that
these pads work best in the final stage of polishing.  For more protracted
repairs and scratch removal I believe the flannel wheels charged with the
appropriate compound are more efficient.

These wheels also require a special adaptor to attach to the spindle of the
buffer and are designed to buff on the edge of the wheel rather than the
face of a bonnet type.  The Menzerna compounds I use come in bar form
(should be available from your Konig distributor) and are applied to the
edge of the spinning wheel.  When buffing on the edge of a 10" wheel, a
great deal of heat is generated and the machine must keep moving across the
part being polished.  The wheel must be cleaned of old compound after
roughly 15 minutes of buffing either with the use of special 'rakes' or
simply a dedicated wire brush held against the rotating wheel.  If you use
different grades of compound it is best to have a separate wheel for each
grade.

In practice, I prefer to go from the finest sandpaper (1500 micro-fine)
directly to the finest polishing compound.  You must evaluate each piece
being buffed as to whether the scratches are fine enough to simply buff
out, or whether they must be wet sanded first.  When buffing the rather
large sanded area that results from a relatively small polyester patch, it
is recommended that you polish the patch area using the hand applied
rubbing compounds (part of the Konig kit) and then use the machine to buff
the rest of the area.  This avoids the need to wait 24 hours for the
material to cure to its hardest, and minimizes the risk of shrinking the
patch with the heat generated from the buffing wheel.

After machine buffing there is usually a great deal of compound dust
sticking to the static charged cabinet.  I sometimes use Windex on a
polishing cloth to pick up most of this dust and then polish by hand with
the Cory High Gloss Polish.

Hope this helps,


Stan Kroeker
Registered Piano Technician

Kroeker & Sons Piano Experts
59 Quiring Bay
Winnipeg, Manitoba
Canada  R2G 1Y5

Ph.   204-669-5881
Res.  204-661-5621