Discovering Electrotype

History, Finding my Way into the Process of Casting by Electrotype

For practical purposes I use a 50 gallon plastic rectangular tank with a working top a metre across and half that width will give the depth of at least a metre suited for the majority of base or high relief pieces I cast in the tank.

The electroplating vat that I built follows the principles laid down in the publication “Philosophical Magazine” of 1836 in an article written by W. de la Rue relating to his experiments with the constant voltage battery as a source of power when he observed that copper deposited by the battery in an acid bath formed an accurate reproduction coating and this could then be stripped off the original plate. From this work an industry was developed led by companies like Elkingtons and many patents and developments rapidly expanded into many fields, both decorative and industrial with the artistic lights in the 1850s and 60s when elaborate candelabrum-epergne nearly a metre high were to be found in the great civic banquets as table centres and in the grand houses built by those made rich in the burgeoning Industrial UK Revolution.

I accidentally discovered a book “Victorian Electroplate” in a secondhand book shop in Brighton in 1975 when looking for secondhand books on bronze casting techniques, having struggled to reproduce my earlier three dimensional animal sculptures by the lost Wax Bronze casting process, with varying degrees of disaster. I realised looking through the book that I might be able to reproduce the copper casting process in my own workshop and acquired the book.

Having looked to acquaintances in the industrial plating business and discussed the chemicals necessary with a friendly chemist, I acquired the secondhand power source, an old plating tank and the essential copper annodes with the necessary commercial solution of copper sulphate with the appropriate percentage of sulpher acid and prepared to reproduce a Reclining Lion on a Rock some 9” long.

The process was a total disaster as I had failed to appreciate that the cavities of the two piece plaster mould I had produced needed to be more conductive than resulted from embedding a circuit of copper wire into the plaster. In any case the plaster absorbed the acid solution over the several hours it was immersed which did nothing for the stability of the mould.

Over a year or so I tried innumerable mould materials and conductive coatings without success until I found, by complete accident, that the two part silicone moulding material I was using which gave me perfect reproduction of the original could be given a conductive surface by dusting graphite powder into the cavity in the mould, the graphite coat could then be polished to give a highly conductive surface to the mould.

I then found by trial and error that twisting two copper wires into a single conductor and encircling the cavity by pinning the conductor into the silicone mould edge with simply made copper clips, so that the complete mould attached by fishing line to a supporting base could be easily suspended in the electrotype tank attached to the conductor bar by the twisted pair copper wire thereby completing a circuit.

I found out largely by trial and error and the help of a couple of people who were professional metal platers in the industrial world that the Electrotype process works quite well if the mould is suspended in an acid solution at 20ºc with the surface area of the copper anodes approximately the same as the cavity I was looking to deposit copper into. If I then control the amps to a ratio of about 20 amps per square footof the one I wished to plate, building up to the full amperage from 5 amps per square foot for the first hour or so to establish an initial key and then progressing the amperage to the full load.

Over time I found I could produce copper electrotype Relief castings up to a metre square limited only by the size of my acid plating tank although a base or low relief casting usually filled more easily than a high relief where the cavities were proportionately deeper.

To overcome these problems I found pumping air via a small separate air pump and a plastic pipe directed at the deepest part of the cavity assisted the plating process, and I also have found shaping or bending one or two of the anodes into an angled bar so that the anode could be positioned closer to the deepest part of the cavity often works to fill the casting over the six to eight hours required for the process.

Although I have many times looked for books or helpful papers on the Electrotype process, I have failed in thirty years to find any, or meet a fellow artist engaged in the process. Indeed I have only very occasionally ever met a sculptor engaged in Relief.

This lack of contact led me to join the British Art Medal Society virtually at its formation based at the Coin and Medallion section of the British Museum. My interest in Relief gave me a natural entry into the fascinating world of contemporary medallion design and the people who design and have cast often in bronze their work.

The Society have a lively and technically, as well as artistically, informed committee and for some time I was a member of this group. As a result of this and my quest for information of the process of electrotype, I was offered the opportunity of going to South Wales to the Royal Mint to see the process of electrotyping they use in producing their stamping moulds for the production of coins of the realm.

Because of the introduction I was privileged to be met and shown around the design and production departments by the Chief Designer himself and a memorable day was spent with the electrotype platers whose techniques, despite the high tech acid baths and control equipment, was handed down father to son in a very traditional way.

Trying to establish some of the plating ratios I might use to benefit my process I was surprised to meet considerable scepticism that I could electrotype anything larger than 6” square (15cm), the largest size of casting they needed to reproduce from the Queen’s head or the various coin obverse designs usually originally created in wax, usually ¾ times la rger than the final coin. From the original a silicone mould is used to make copies in plaster and reduced via the electrotype and a bank of reducing machines to form the coin sized steel dies necessary to stamp the actual coins of the realm in millions.

The platers were helpful but most sceptical that I could produce anything of size I claimed for my work and although we parted in most friendly terms as working artisans, it was only some months later that the supervisor visiting London for a conference visited my home and workshop where he saw for himself by trial and error, and because I knew no better, I had been able to electrotype larger pieces of work using my rudimentary process. I was delighted to receive the handwritten process specification used by the Royal Mint in the mail some days later and felt one of a small bank of professionals as a result.

DB