Amen to D. L. Bullock's remarks about the stripping older pianos and
organs. What we know now as "Shellac" is what used to be called
"Varnish." Please be advised that what we now know as varnish is
Shellac, as Mr. Bullock stated, is readily washed off with alcohol.
I usually buy denatured alcohol by the two gallon can and use it as
needed in a small dish similar to some cereal bowls. I then saturate a
cloth in it and start over the old finish to soften it. With a liberal
application of alcohol the finish will soften up and then can be washed
off with another cloth loaded with alcohol.
On a bet one day I stripped the case of a Mills Violano in less than one
hour and when it was dry it was ready for any filler and sanding that it
needed and could have been refinished the same day.
I also have seen instruments, including a Seeburg Style H, that were the
subject of varnish remover, lacquer thinner, and paint remover and then
were refinished with epoxy. Well, it looked really shiny but I certainly
wouldn't want any of my instruments treated that way.
If you want to refinish an instrument of prewar vintage you will probably
be dealing with Shellac and using a proper refinishing schedule and some
muscular application you can put what's called a French Polish on it and
it will look beautiful, almost liquid in appearance, as if you could dip
your hand right down into it.
If the occasion arises that you don't want to do a refinish on a piano or
organ where the Shellac has "crazed" due usually to dryness, you can help
the finish temporarily by using a paint brush and painting denatured
alcohol on with a paint brush. I usually use a one inch brush.
This softens the Shellac enough so that when it is left to dry it will
form a new surface without the "crazing" or cracks in the surface. It's
a cheap fix but some people don't want to pay for the full shot.