Last week Jonathan Brecher asked for information about his "negative-image (incuse and reversed) electro-somethings of the Pistrucci Waterloo medal."What Jonathan Brecher has, as illustrated in last week's E-Sylum, is an electrogalvanic mold. I am delighted to furnish him the following information on his electrogalvanic item.
Dick Johnson submitted this analysis of Jonathan's pieces, which includes a detailed description of the electrotype process. -Editor
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!
Medalmakers have a saying about this: "If it is in the model, it is in the medal." Here are some highlights in the history of electroforming:
Jonathan Brecher adds:
Fabulous! That makes a LOT of sense. Given that there are at least two different types of wax, I wonder if that means these molds were actually used in production over a longish time period, where the wax would need to be touched up from time to time.
I wish I could prove the provenance back to Pinches. Unfortunately, this came from an estate sale. Whatever the previous owner knew, it's been lost.
I'll definitely try to track down a copy of that ANA Journal. I'm not actually collecting electrotypes, but I've picked up a few that I like, and I definitely don't know as much as I could. Thanks, Dick!
Dick Johnson adds:
You have made a correct assumption. The evidence of two kinds (or colors) of wax could very well indicate it was cast at two different times. This could be decades apart! Electrotypers generally only keep one kind of wax on hand. In fact, you could have this done now.
If you would like to see this process in action -- or if you would like to have a positive made from your mold -- I recommend you bring your mold to the following firm to have this work done, they are the America's most expert medallic electrotypers:
Greco Industries, Inc.
Ricky Greco, VP
Francis J. Clarke Industrial Park
14 Trowbridge Drive
Bethel, CT 06801
Phone: (203) 798-7804
This firm is in a brand new $3 million plant. It was founded by Hugo Greco, former head of the finishing department at Medallic Art Co in New York City. He just celebrated his 50th year in the field. The Greco family brings a great deal of Italian craftsmanship to their work.
As I have mentioned in a recent article in MCA Advisor, foundry casting can reproduce detail down to 1/100th of an inch, die striking can reproduce detail down to 1/1000th of an inch, but electrogalvanic casting can reproduce detail to the width of an atom!! It is far more detailed.
To view all of Jonathan's photos as a slide show, see: Pistrucci Waterloo Medal electrotypes (http://www.flickr.com/photos/coinbooks/sets/72157606974566395/show/)
Wayne Homren, Editor
The Numismatic Bibliomania Society is a non-profit organization promoting numismatic literature. See our web site at coinbooks.org.
To submit items for publication in The E-Sylum, write to the Editor at this address: email@example.com
To subscribe go to: https://my.binhost.com/lists/listinfo/esylum
All Rights Reserved.
NBS Home Page
Contact the NBS webmaster