WHAT DID PHILADELPHIA MINT USE ELECTROLYTIC TANKS FOR? Público Deposited
QUIZ ANSWER
- We've had several responses to Dick Johnson's quiz question: "The Philadelphia Mint had electrolytic tanks from 1855 until recently. Yet, they never plated a coin or medal (to my knowledge, at least). What then, did they use these tanks for?" -Editor
David Ganz writes:
I believe they plated the dies to extend their life.
Joe Boling writes:
The mint's electrolysis tanks were for making galvanos - not unlike the BEP's use of them now to make printing plates. Siderography is a dead art.
Dick Johnson writes:
Readers who may have a long memory (or great knowledge of Mint activities) will have easily supplied an answer. It was given in my earlier E-Sylum article Electrotyping in America (August 1, 2010).
The answer: The tanks were used for electrolytic casting of dieshells, hubshells and galvanos.
So there's the answer Dick had in mind when he asked the question. Joe Boling was the closest. But were there additional uses? -EditorRon Abler writes:
I believe that electrolysis was used by the Philadelphia Mint first and then later at the Denver and San Francisco to refine metals for coinage.
Ken Bressett writes:
Elementary, my dear editor. They were used for making electrotype copies of rare coins for use in the production of an early form of printing plates, and occasionally for use in a display in the Mint exhibit. They even went as far as making electrotype copies of their famous 1804 dollar for some nefarious purpose.
I shared all the responses with Dick Johnson, who had this to say. -EditorHooray! Our readers are not moribund! In reply to Ken Bressett: Always authentic information from Ken. Correct on all counts.
In reply to Dave Ganz: Chromium plating first occurred at the Royal Canadian Mint in Ottawa in 1930 on the collars (but not the dies) to extend their life for striking the very hard high-nickel content five-cent pieces. By this technology the same mint chromium plated dies in 1942. Some pieces were struck only on one side with chromium plated dies. This gave a glossy surface to the struck piece. Can you find any of those one-sided glossy varieties on World War II Canadian coins? By 1945 the Ottawa Mint was chromium plating all dies, and this technology spread to other world mints. That glossy surface is sometimes described by collectors as "prooflike" but this is completely different from proof polishing of dies (which collectors call "full proof").
In reply to Ron Abler: The refining of metals by electrolysis is a different technology, even though both use the same word "electrolysis" (sorry, that's the shortcoming of the English language). Refining electrolysis breaks out the desired metal. Electroforming by electrolysis adds the desired metal to the pattern (which is called by many names: metalworkers call it a "core pattern" or "mandrel," mint workers call it a "dieshell" or "hubshell" depending upon whether it is negative or positive, in England it is even called a "former").
I also received this from Paul Lajoie:
"Didn't the US Mint electroplate the bronze and silver US Bicentennial medals? The ones that are silver dollar size? Also, did they not make many of the military medals, some of which are obviously electroplated?"
I am unaware of either of these. Does anyone have any documentation of this occurring?
I followed up with Ken Bressett for more information on how the process was used to create coins images for books. -EditorKen Bressett writes:
The electrotype process was used (although not invented) at the Philadelphia Mint around 1841 in order to make copies of coins that could be traced with a ruling machine and not harm the original specimens. The printing plates that were produced by this technique were used in the 1842 A Manual of Gold and Silver Coins by Eckfeldt and DuBois. The prints were described as “engravings of coins executed by the metal-ruling machine under the supervision of Joseph Saxton”.
A description of the process in the book states that this is a unique process developed at the Mint using the latest technology of electroplating, metal ruling and images taken from actual coins. The results are surprisingly good, but the process was soon abandoned by use of photographic images and other techniques.
Electrotype copies of printing type have been used even before that time (especially in Europe) and continued on up until very recent times, to save wear on the precious original metal type, and extend the life of printing forms especially on long press runs.
Thanks, everyone, for your great responses. Excellent topic! -EditorTo read the earlier E-Sylum articles, see: A PRIMER ON PLATING FOR ALL COLLECTORS (www.coinbooks.org/esylum_v13n46a05.html)
DICK JOHNSON ON ELECTROTYPING IN AMERICA (www.coinbooks.org/esylum_v13n31a16.html) - 2010-11-21
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