What are Enamels

History

Art Enameling on Metals by H.H. Cunynghame  1906

Metals such as gold, silver, iron, copper and fine brass; copper with a small amount of tin, are capable of being enameled. But nickel, zinc, or common brass, which contains a mixture of copper and zinc are not capable of being enameled.  Mr. Cunynghame, first speaks of the art of enameling is simply melting glass on to the surfaces of various substances capable of adhering to it and also capable of withstanding the heat necessary to melt the glass and cause it to flow. Mr. Cunynghame, speaks of the common technology of producing Crockery, with is clays consisting of silicate of aluminia and magnesia, and forming it into shapes and firing it. After this process it is know as biscuit ware, and is hard and porous. At this point glass ground to an impalpable powder is mixed with water and the vessel dipped into the glass slurry, dried and fired to the melting point of the glass. In this respect the glass is called “glaze.” Very similar to our enameling and as well as the commercial applications of enamels or glass on other foundations such as iron= stoves and refrigerators or bathtubs. And don’t forget the use of enamels on signage.

Glass consist of sand and an alkali such as soda or potash, fused together with the addition of ingredients to produce color. He states the peculiar value here of lead. It gives the glass the remarkable ability to adhere to and run over the item being enameled and prevents it from cracking. He state it makes the glass more elastic and enhances its’ ability to withstand extreme temperature changes.  He also says that glass without lead is not suitable for enameling, as it will crack away from the metal.

Coefficient of thermal expansion is when the temperature of a substance changes. The energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling. This dimensional response to temperature change is express by its coefficient of thermal expansion. To be continued…..

Glass is colored by melting it with the oxides of various metals. Oxide of tin makes it opaque white, iron gives it a sea green and yellow, cobalt a royal blue, and copper a turquoise blue. Manganese colors glass violet, silver and antimony yellow, and gold crimson. Also we have chromium, producing a fine shade of green; uranium, a fine yellow; and iridium, giving enamels the shades of steel gray and black.