I was, and still am, reluctant to enter this debate but, since another
subscriber has mentioned nitrocellulose, here goes.

Nitrocellulose is the major ingredient in "flexible collodion" which
can be obtained at most drug stores.  Many years ago I came across the
following formulae:

  3 parts to 1 part acetone for sealing leather.
  1 part to 3 parts acetone to harden piano hammers.

John Powers
Harpswell, Maine