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MMD > Archives > October 2010 > 2010.10.31 > 05Prev  Next

Refinishing Shellac Based Finishes
By Randolph Herr

I have gotten a few requests to give more details on a "refinishing"
technique that I may have read about or maybe I made it up myself, but
regardless, it is an easy way to make old finish look a heck of a lot
better with minimal work.  Basically, it consists of using an atomizer
or spray gun to apply wood alcohol to a piece of wood with an old
shellac-based finish.

Since so many people have personal definitions of what constitutes
"shellac", "resin", "varnish" and "lacquer", there is bound to be some
needless arguing if these terms are not strictly defined, and I will not
define them here.  Until the mid 1920's, all pianos were given a finish
that was shellac or a varnish made of shellac and a resin.  After the
mid 20's, just about all pianos were finished in a nitrocellulose
lacquer that was so much faster and easier to apply that it pretty much
killed the shellac finishes.  While I have seen very nice lacquer
finishes, I think that a shellac based finish is the nicest of all.

In any event, let me describe my technique: The first thing is to see
if the finish is alcohol soluble.  On an inconspicuous spot, see if
wood alcohol makes the finish sticky.  If not, then stop here.  But if
it does, then you must clean the surface completely since if you are
going to soften the finish, any dirt or foreign material will soak into
the finish and be impossible to remove.  Once you have cleaned the
surface by steel wool, light sanding, washing with paint thinner
(mineral spirits) or any combination of these techniques, you are ready
to start restoring the finish.

The first thing to point out is that wood alcohol is a deadly poison,
and it is made that way to prevent people from evading the liquor
taxes.  Therefore, it stands to reason that breathing in atomized wood
alcohol is not a good idea, and you should take precautions.  Another
point is to work in an area that has sufficient light so that you can
see when the wet surfaces begin to become reflective.  It is important
that you neither keep the wood with a dry look, nor should you put on
enough alcohol so that it runs or puddles on the surface.  The first
coat you give will make the wood look about 99% as good as it ever will
look, so keep in mind the law of diminishing returns.

After it dries, it will not look as good as it did when wet, so more
spraying is in order, with you being the final judge on how many times
you spray each piece.  One thing I have not yet done, but seems like a
good idea is to mix in some new shellac with the alcohol being sprayed
so that you are not merely amalgamating the old finish, but adding new
material as well.  It might be better to add the shellac in the second
or third sprayings, but I have no experience to help you here.

I think the reason you can get such amazing results is that you are
leaving both the filler and the stain in the wood that was applied
100 years ago by master finishers.  If the finish is ever washed down
to the bare wood, new filler and stain will have to be applied, and
you are not likely to be as experienced or talented or patient as the
old master finishers.

After you have let the wood dry for a few days after the final
application of alcohol, you can use a number of things such as
sandpaper, steel wool, rubbing compound, etc. to give the wood its
final look.

One thing I have wondered about is if this technique would work on
a modern lacquer finish if you sprayed lacquer thinner instead of
alcohol.  If anybody has ever tried this, let us know.

Randolph Herr

(Message sent Mon 1 Nov 2010, 00:33:41 GMT, from time zone GMT-0400.)

Key Words in Subject:  Based, Finishes, Refinishing, Shellac

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