[ Don Keil wrote in 080225 MMDigest:

> You can make a useful dull black spirit varnish by dissolving
> an old shellac 78 rpm record in denatured alcohol.

Not a bad idea, but be aware of the composition of these artifacts:

 * shellac (exudate from Asian bugs, usually)
 * carbon black (or whatever color the record might be, e.g., red)
 * gravel

The idea is that there is considerable grit filler in 78 rpm records --
finely ground, but mud nonetheless.  This was done to make the playing
surface harder than the needle, so as to etch the needle to the groove
contour as the record played.

A brilliant solution in terms of materials science, since the needles
are much more readily changeable than the records.  However, this is
also why you should change your needle after every play, since the
groove contours will doubtless vary between records, and why the lead-in
grooves are usually hammered the worst (from reshaping worn needles).

In any case, it seems to me that the mud will tend to dull the finish.
Better simply to add carbon black to shellac.

A. B. Bonds