The E-Sylum:  Volume 9, Number 44, October 29, 2006, Article 17

MONOGRAPH ON NUMISMATIC ELECTROTYPES IN THE WORKS

Dick Johnson writes: "Bob Lyall's comments in last week's E-Sylum in
response to my item the previous week on electrotypes is hereby noted.
I stand by my statement that electrotypes are cast. It is just a form
of casting you might not think of. It is a form of "electrogalvanic
casting" from the field of electrometallurgy (in contrast to die
striking). There are a half dozen forms of casting, the most common,
of course, is like foundry casting, and this is perhaps what Bob
thinks I meant. Sorry I wasn't clear, Bob. But the "cast" term is
correct.

Bob goes on to explain in general the electrotype technology. The
oil he mentions is a "release agent," and not a good one at that
(it is too thick). Let me state my experience with electroforming
and electroplating. This technique is widely used in the manufacture
of medallic art and pattern making for dies. From many hours,
hundreds of hours, leaning over the electrolysis tanks, this
technology became embedded in my mind while I was director of
research at Medallic Art Company. I also had to explain this
technology during many plant tours by visiting VIPs (from local
coin club members to artist Andy Warhol).

First of all, to make a replica of a genuine coin it is best to
make a plaster cast of each side so you do not damage the original
coin. (You need a release agent for this also -- don't let plaster
come in contact with the original coin -- it will get in the
crevices and is next to impossible to remove once it hardens!).
Then you can make an electrotype from those casts (and later
affix the electrotype shells together). Casting changes polarity,
so it is necessary to have the negative plaster to make a positive
anyway.

Instead of using oil, we used bronze powders - the finest, flaky
form available. This is ideal for two reasons: it is electrically
conductive and it acts as a release agent (after the electrolytic
cast is made and to break it away from its pattern). Bronze powder
must cover the entire surface; it can be applied in a very thin
coating (so it does not alter the design as the oil would do
minutely).

Bob Lyall is partly correct in mentioning silver nitrate in the
electrolyte solution, but you must also have a cyanide chemical
(as well as water and one other chemical) to effect the transfer
of ions from the anode (the silver bar) to the pattern. The
coin pattern must be wired to a rectifier which is the source
of a very low voltage direct current.

All this technology will be explained in a monograph John
Kraljevich and I are writing on Numismatic Electrotypes. We just
recently discovered an eight-page manuscript by Elvira Clain-Stefanelli
who translated a small portion of an Italian work on the subject.
The technology therein blew our collective minds! We will reveal
this all in our monograph.

We recognize the vast misunderstanding of this technology in the
numismatic field. A recent example is an article on the Libertas
America medal in the September issue of "Numismatist," page 54,
which states "At least one numismatic expert with whom he spoke
raised the possibility that it is an electrotype (but such pieces
usually are exact duplicates of the original (including depressions,
scratches and other diagnostics) AND MADE OF LEAD."

Impossible! Lead does not conduct electricity. Electrotypes must
be made of a metal that conducts an electric current. The major
coinage metals – copper, silver, gold – are excellent conductors,
thus ideal for coin electrotypes.

I had not heard the story of the British Museum buying back their
own electrotype. I love it! Can anyone document this? We would
like to include it in our monograph."

  Wayne Homren, Editor

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