NNP

Electrolysis.  The physical and chemical process of passing a low voltage direct current through a liquid electrolyte containing a solution that carries ions of anodic metal to deposit on the cathodic work. Making electrotypes, electroplating, electroforming, electrostripping, galvanoplastics, galvanizing, anodizing are all possible because of electrolysis.

Electrodes, one positive and one negative, are introduced into a liquid electrolyte. The current – must be low voltage direct current controlled by a rectifier – is passed through the liquid. Charged particles, ions, leave the anode electrode, pass through the liquid, and deposit on the cathode electrode, forming the circuit. The speed of this transfer is called the migration velocity and is depended upon many factors. In addition to the current voltage and the type of metal electrodes, the type, formulation, temperature and acidity (pH) of the electrolyte is also important, as is the metal salt dissolved in the tank. Controlling all these variables is the mark of an experienced electroformer.

Positive ions leave the anode joining other positive ions of the metal in the electrolyte solution. These are attracted to the negative cathode where a physical change occurs causing the metal to be deposited. (Care must be taken in the process at this point that the ions deposited on the metal do not change to a gas where it is liberated through the electrolyte.)

In coin and medal technology, electrolysis is vitally important in making oversize patterns or galvanos – called dieshells or hubshells – from which coin and medal dies or hubs are made by reduction on the die-engraving pantograph. plaques, too large to be diestruck, are ideally made by electrolysis and are limited in size only by the size of the electroforming tank. Electrolysis is also used in restoration work by removing unwanted metal deposits on coins and medals.

History of electrolysis.  In 1791 an Italian, Luigi (or Alolsio) Galvani (for whom

galvano is named after), first observed electric current. Another Italian, Alessandro Volta (for whom volt is named after), in 1800, developed the voltic pile (the principle for stored current). An Englishman, Michael Faraday, developed the generation of direct current in the 1830s. But it was a German, Moritz Herman von Jacobi (1801-1874) who developed, in 1837, the process he called "galvanoplasty" which today is known as electroforming.    

In 1840 George Richards and Henry Elkington received the first British patent for silverplating, marking the date for the development of electroplating. It was the silverware industry which quickly embraced electroplating, providing tableware in silverplate for the masses. All electrolysis was conducted with primitive batteries until 1889 when commercial electricity became available in America. (We have Thomas Edison to thank for much of the development of commercial electricity, as generating stations, transmission of electric current and, thusly, modern electrolysis.)

In addition to the silverware industry, electroplating was developed by the jewelry industry, and the introduction of commercial electricity in 1889 made this a widely used branch of jewelry making. Medals were plated in gold and silver early in this developmental period, replacing firegilding, and grew more so after the availability of inexpensive electricity.

References:                                                                                                                       

F1 {1962} Graham.

excerpted with permission from

An Encyclopedia of Coin and Medal Technology

For Artists, Makers, Collectors and Curators

COMPILED AND WRITTEN BY D. WAYNE JOHNSON

Roger W. Burdette, Editor