Joel Orosz writes:
Vol 11, No 36, September 7, 2008, "Dick Johnson on Electrotypes"
Another wonderful function of The E-Sylum, providing a forum for an expert to provide a plain-English explanation of an abstruse topic.
Jonathan was particularly concerned about the wax coating on this piece. He said "I've shown these to several people, and nobody seems to know what to make of them." This is understandable. Electroforming, the electrolysis process, and even electrotypes are one of the least understood concepts of all numismatics. This is why I have joined with numismatist John Kraljevich in the preparation of a monograph on the subject, Electrogalvanic Casting In Numismatics. This has been mentioned previously in E-Sylum (vol 9, no 44, art 19, October 29, 2006).
This was mentioned prior to the publication of one of the few (and best!) articles on the subject. Red Book guru Kenneth Bressett wrote "The Nature and Use of Electrotype Reproductions" which appeared in the now defunct ANA Journal, spring issue 2007. Well worth obtaining that issue for reading that article alone.
An electrogalvanic mold is the pattern for casting electrotypes or galvanos. The pattern can be most any composition. The U.S. Mint was using iron in the 1850s; the British Royal Mint was using iron as late as 1886. But the pattern can be plaster, any other metal, or even carved wood (the later has to be specially treated to close all the tiny pores in the wood). A wax pattern is usually cast in plaster before it is used in the electrogalvanic process.
The pattern must be specially prepared: (1) the surface to be reproduced is coated with bronze power to make it electrically conductive -- this also acts as a release agent to remove the casting afterwards; (2) it is wired, two copper wires are attached to the pattern's surface to carry the electric current to a bus bar above the tank where the electrolysis takes place, these also support the pattern and its galvanic casting while it is in the tank; and (3) the area where no deposition is to take place is coated with wax, this is a stop-off (the British call this a resist).
The wax on Jonathan's electroform is this resistant material still intact. It covers the entire back, and the portion of the front, the flange, where no metal is to be deposited. If this were not done the metal would deposit on both sides, all around and entomb the desired electroform.
The wired and prepared pattern is immersed in an electrolyte solution in the tank. This solution is slightly acidic but also contains cyanide. Electrotypers have experimented for decades to replace the deadly cyanide, but found it is best to use in electrolysis. The solution must also contain ions of the metal to be deposited. Most metals can be electroformed. In numismatics it is the same as coinage metals, gold, silver, copper. The process is the same as goldplating, silverplating, copperplating. (Other metals are plated in the jewelry field, or even chromium plating in industry.)
A tank large enough to contain the suspended pattern contains the electrolyte solution. It also must have anodes present. If you are creating a copper electrotype, you must have several pure copper anodes suspended in the solution as well. Separate tanks for each metal. The anodes are sacrificial -- they wear away like a bar of soap -- ions of the copper in the anode pass into the solution and deposit on the pattern's treated surface, this is the cathode, when the electric current is turned on.
The current must be a low voltage direct current and must form a complete circuit. A rectifier converts AC current to DC and is wired to bars from which the anodes are suspended. The current passes into the anodes then into the solution, onto the cathode pattern, up the copper wires to the bus bar and back to the rectifier. Circuit completed.
It is fun to watch gold or silverplating. It changes the color of the anodic metal in about 15 seconds. But usually it requires about three days to deposit enough metal, say a 1/16th inch, to give the electroform enough strength so it won't malform. This form is also called a galvano. After that time the ensemble of pattern and electroform are removed from the tank.
They are separated. If any opening is found a screwdriver is inserted between the mold and the cast galvano. It is pried open a little more. The electrotypers' trick of the trade is applied. Compressed air is blown into this opening and the two snap apart.
Jonathan's electroform is negative. As a negative mold it makes a positive cast.. (Casting always reverses polarity.) His photo shows a hanger. This was not used in the electrolysis process; it was intended to hang on a wall. How much more realistic to have the original two copper wires intact.
If Jonathan can prove the provenance of this piece back to Pinches, it may have been the original one Pinches used in 1849 to make the first Waterloo Medals. However, once you have one of these medals anyone with electroforming equipment and the required skill could copy it by creating the pattern for casting these medals anew. Unlike foundry casts, however, subsequent electroformed castings do not shrink, they are the exact same size as the original, so size is not a diagnostic.
Operating a successful electrolysis is not easy. There are a many variables, chemical composition, pH, temperature, placement of the pattern in relation to the anodes, the electric circuit, the ionic balance. It takes considerable skill. That is why you will not find many electroformed copies.
Possibly Jonathan's pattern could have been made in the United States. It could have been made by one of the New England silverware firms (1850s) or by New York City electrotyper Samuel H. Black as early as 1859. Or by a specialized electroforming firm as early as 1884. We have a list of a dozen American electrotypers and are compiling the known electrotypes they made.
The most important thing you should remember about electroforming -- it replicates minute detail. In comparison with other methods of making numismatic items: foundry casting reproduces detail down to 1/100 of an inch, die striking reproduces detail down to 1/1000th of an inch, but electroforming reproduces detail down to the width of an atom!
Dick Johnson is a regular fixture in The E-Sylum, providing some content for nearly every issue. Some of his items are among my favorites as well. Few people in numismatics today have the depth of knowledge and experience at his level. It is a pleasure to be able to pass some of his wisdom on to a new generation of numismatists.
To read the complete original E-Sylum article, see:
DICK JOHNSON ON ELECTROTYPES
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