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Parent Category: Technical Articles from Journal Back Copies

Category: Technical Articles 2005

Notes received from a Guild member (following Tony Stephens' last editorial) in case any other members are having trouble with impurities in their copper.

It is stated in the Thomson Enamel Workbook that not all grades of copper are suitable for enamelling. Lack of adherence and bubbles may result from using impure copper. Electrolytic copper is the minimum specification and to be absolutely safe, oxygen free copper is ideal.

Suppliers in the US (principally Thompson Enamels) sell copper for enamelling that conforms to ASTM B-170. This is electrolytic copper that is oxygen free. It produces no products that can diffuse to the surface on heating and which could cause bubbles and pits in the first fluxed enamel coat. The corresponding European specification is EN 1976 CR007A and CR009A.

In the UK, there is a more relaxed approach to the grades of copper for enamelling and such suppliers are often unable to indicate the grade of copper they are marketing.

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