This is the answer to a thread found in the Reed organ Society
listserver.  Some clown planned to sandblast the finish off of his reed
organ case and got some very negative responses.  I thought it might
interest MMD as well.

Sandblasting is a useful but highly dangerous item in the restoration
shop.  I have used it for years, and will use it far more when I get a
cabinet to prevent the mess.  I used to go outside to use it and still do
from time to time.

However, I have never been able to use it for finish work.  It is
so easy to just wash the organ case in Denatured Alcohol, why bother
sandblasting.  The alcohol removes the shellac without removing all the
patina.  Of course, one hint is to not take 100% of the finish off.  Just
keep washing until the glop comes off and do not do the final to-the-wood
scrubbing.  Then replace the missing shellac and then French polish.
(This is a skill, not a substance or product.)

My experience with sandblasting the finish off left me with wood that
looked like old barn wood.  It was all bumpy where the soft part of the
grain was removed and looked whittled out, while the hard grain was
raised.  Also if the finish is tenacious, the spots where the finish
was will be raised and the rest will be whittled out.

I have seen organs done this way and the are this way all over.  Talk
about work, try sanding one of those down until it is smooth.  I have no
experience with nut shell, corn cob, but glass beads and #2 urn sand work
well for non finishing purposes.

The main use for sandblasting is for metal parts but I also use
Scotchbrite pads, brushes and soapy water if they are not bad.  I used to
use blasting as well for the tops of piano keys, the wood part only, but
I now also wash those.  I have blasted piano actions as well.  In piano
actions it brightens up the wood but it MUST be WELL blown out of the
action as leaving any of it in will grind down the parts as they work.

Since we now do only like-new restorations, we expect our finished
instruments to last 50+ years.  We no longer sandblast parts unless they
are getting all new flanges and the piano is to be completely
disassembled.  This insures that the sand is ALL gone.

Most of the reasons for sandblasting wood can be done better and with
less damage by washing in Rose cleaner and hot water.  Of course, you
MUST make sure it air dries as fast as possible.  (in front of a fan or
in the sun, and it must not be laid flat.)  I learned this from an old
pipe organ restorer and I have never in 10 years had any wood warp from
this process.  Also, of course, I never get the reed chambers wet.  I
have reconstructed enough reed chambers to their reed pans to even
attempt anything like that.

I use sandblasting for player and reproducing piano metal parts when they
are rusty.  This is why we can restore those instruments that others have
written off as unrestorable.  I do not sandblast the piano plate unless
it never had any jesso on it.  That is the black stuff that lies under
the gold paint and smoothes out the sand-cast look on the cast-iron.

D. L. Bullock    Piano World    St. Louis