If you want to strip the old piano finish without removing patina,
then the gentle method is the way.  This is only for pianos that have
original finish and no paint over that.

The old finish is shellac.  It will melt off with denatured alcohol or
methanol.  I will tell you my old method.  Slop methanol on the surface
liberally with a brush.  Cover the surface with waxed paper from the
grocery store.  Leave it until the finish has softened (10-15 min.).
The old finish can be shoveled off with a plastic spatula or squeegee.
When it is clean you can wet it further and keep cleaning it off with
rags saturated in methanol.

You do not want to remove all the finish but only the top several
coats.  The bottom coat must stay so don't keep putting fresh solvent
on after it is mostly clean.  I do not like steel wool as it leaves
tiny rust spots inside new finishes many times, as it breaks off
microscopic metal pieces.

At the point when it is clean of thick coats of shellac I do a fine
sand and go back with new orange or "Amber" shellac, as they now call
it.  Once the color of the wood is as dark as you want it, then change
to clear shellac.  Behlen makes some very nice "blonde" shellac flakes.
That is the best clear I have found.  The best way to buy shellac is in
flake form and mix it yourself with methanol.  (It has to set overnight
to dissolve the flakes.)

Once you begin working with shellac you will come to prefer it.
Once you get a good buildup of shellac you can French polish it to the
original mirror finish.  It will then be as it was originally.

French polish is not a substance but a technique.  The ingredients are
shellac, solvent, and linseed oil and most important: the right rag.

This stripping technique will be slower than the big commercial
methods.  However, you avoid the bleaching, washing, staining, and
sealing steps so it is often faster than what everyone has been
brainwashed into doing by the big chemical companies.

By the way, if methanol does not strip fast enough you may mix 50-50
methanol and lacquer thinner and get your basic gentle but slightly
stronger stripper.  The old guys used to also add acetone if the finish
was particularly stubborn.

D. L. Bullock    Piano World    St. Louis