LACQUERING'S BAD RAP. Publique Deposited
The E-Sylum: Volume 5, Number 5, February 3, 2002, Article 15
LACQUERING'S BAD RAP.
Regarding Ron Guth's item on the Milwaukee's Museum
Cleaning & Lacquering, Dick Johnson writes: "While cleaning
coins is another story, lacquering coins has gotten a bad rap
in the numismatic press for years. It is a coating placed on a
metal numismatic item that prevents toning, tarnish and some
abuse. Literally, it can preserve the original condition of a
metal surface if it is applied properly and shortly after the item
is struck. This was widely done by some real old-time
numismatists for preservation, but this was before slabbing
and air-tight plastic containers. (Did they know something
that has been forgotten by modern numismatists?)There are numerous kinds and colors of lacquers but is
basically a clear shellac. Most trouble comes from
inexperienced application. It should be applied as lightly as
possible but must cover the surface completely. Since the
ideal lacquer used for coins is clear, you cannot see it when
you apply it. Lacquers are widely used in the manufacture
of better medals. These are often tinted.It is best applied with a spray gun (the finer the nozzle
apertures the better). Since the spray disperses into the
air, a mask for the operator and a spray booth must be
used (required by OSHA!). In medal manufacturing the
medals are baked (to remove all moisture), laid out on
a wire tray about 12 by 24 inches, and this placed on a
turntable inside the booth. One pass of the spray gun
west to east and back. The tray is rotated 90 degrees.
Another pass and back. It dries immediately. A tray
is placed over the medals and the entire ensemble held
tightly and flipped over. Then sprayed again like before
(on the opposite sides).Inexperienced collectors are tempted to use lacquer
from a spray can (or worse, brushed, or dipped!).
Inevitably, they apply too much lacquer and it builds up
in crevices and goops at the sides of letters and relief.
Instead of a few microns of lacquer covering the surface
it is far, far thicker. This can be seen -- and it's unsightly!
Thus the reason for the bad rap.Incidentally, two petroleum products should be on hand if
you have a large medal collection: TOLUENE (to clean
lacquered surfaces) and ACETONE (to remove the lacquer).
Both are highly inflammable -- you must know what you are
doing! Caution: after removing the lacquer the surface is super
sensitive to toning (called ACTIVATED SURFACE) and will
begin toning within two week's time."- 2002-02-03
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