An Investigation into Using Enamel Flux on Copper

By Raymond Jackson

Introduction

As a relative beginner in the craft of enamelling, I find myself especially attracted by transparent enamels. They yield their true beauty when light is reflected through them from the metal substrate beneath.

Copper, being much cheaper than silver, is a popular metal base for enamelling. However, the copper oxides that form at the high kiln temperatures necessary to fuse the enamel to the metal can both colour the enamel and reduce the transmission of reflected light. Some transparent enamels are little affected but most appear somewhat opaque and dark. As a consequence it is generally good practice to first apply a colourless enamel flux. This flux is formulated to more easily absorb the copper oxide. The result should be a clear and bright surface onto which coloured transparent enamels can then be applied.

The proper application of enamel flux is thus an important first step in achieving reflective enamel pieces with copper as the base metal. In contrast, silver presents problems only for specific enamels (eg some reds and oranges) and the flux layer is correspondingly less necessary.

Through my inexperience and understanding of the factors involved in achieving transparency with enamel flux, my enamelled pieces were rarely clear or bright, and more often they were muddy, or cloudy.

I decided, therefore, to embark on a series of experiments aimed at finding and controlling the factors that determine the clarity of enamel flux applied to copper. These experiments deal with the sieving of dry enamel flux powder on copper. Most of the results, however, are also relevant to the technique of wet laying of enamel flux.

This report describes those experiments that have subsequently led me to achieve a consistent and acceptable enamel flux base coat.

The information is presented in the hope that other beginners may find it useful. It owes much to various excellent publications that provide background information on the fluxing of copper.

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Relief Electro-Etching for Champlve

By Raymond Jackson

Introduction

In the Guild of Enamellers Journal, (Spring 2000), Dorothy Cockrell described how to build an electric etching kit and to prepare small pieces of copper or silver for etching using a weak solution of acid. It is a relatively safe and clean method of producing items for Champlevé enamelling.

At that time, I was relief etching copper using the more conventional Ferric Chloride solution. Relief etching is the eating away of large areas of metal as opposed to line etching which results from scribing through a pre-applied resist. Ferric Chloride is not a very agreeable chemical and the etching process creates bubbles and deposits and the solution must be carefully disposed of when exhausted. A development that alleviates the unpleasantness of Ferric Chloride is Edinburgh Etch. This involves adding citric acid to the solution and this speeds up the process, dissolves the sediment, creates less bubbles and the solution has a longer life.

Despite this improvement to the mordant, I was keen to try electro-etching as it uses less aggressive chemicals and it should give a more controllable etch. Starting with Dorothy's work, I have gradually progressed with this technique. In doing so, I have relied heavily on the work of Cedric Green, (see References), who has explained and identified the benefits of using copper sulphate solution as the electrolyte and the use of new resists. He places considerable emphasis on the benefits of using non-toxic chemicals for etching copper and other metals. Although his work is aimed primarily at the printmaker, much is of direct application to Champlevé enamelling.

So I have set down theses notes of my own experiences with electro-etching copper. My work is not definitive and there are many other techniques for electro-etching copper. Others embarking down this road may, nevertheless, find the information helpful.

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