Removing old polish residue

an ultrasonic is a powerful and dangerous tool to use on historic
objects, because whatever you remove in the first few seconds becomes
blasting medium to "sandblast" the freshly exposed surface.

When one absolutely MUST use an ultrasonic (for example to remove wax
buffing compound), the object should be placed in a glass beaker of
clean solution, on a piece of filter paper to prevent burnishing the
bottom contact points with the glass as the piece is bounced around, and
immersed in the us tank no longer than 20 seconds before removing and
examining under magnification for effect.  The solution must be changed
before repeating the treatment.  The damage caused without these
precautions is simply not warranted in responsible conservation
treatment.

Lisa Mibach

                                  ***
                  Conservation DistList Instance 7:72
                  Distributed: Monday, April 11, 1994
                        Message Id: cdl-7-72-002
                                  ***