When I first started playing with enamel in the SCA, one of the more common comments I would get is “that’s not period.” And while I knew that was true, using a torch to fire the enamel was a quick and easy way to immerse the folks participating in my workshops into this ancient art. I still continue to use my gas torch and my electric kiln for most of the enameling that I do for the SCA. But there’s always been that thought, niggling at the back of my mind… “so how did they do it?”
So like any good Scadian, I put on my research your hat – I read through a many a blog post, Wikipedia pages, and scanned many texts. I found a bunch information in Theophilus’ book, On Divers Arts pertaining to how enamel was fired in the medieval period. I wrote up a blog post (see below) on the process of creating the Theophilus Forge Muffle Furnace. Thompson Enamel, a company based in Kentucky
But as one thing often leads to another, I began to think about some of the other details involved in the process. The ground glass we use (commonly made up of silica, soda, lime, and a small amount of borax) gets its color from the addition of certain elements, mostly transition metals, including cobalt, manganese, iron, cadmium, selenium, gold etc. These metal oxides react with a range of variables including the base metal, the off gassing of the heat source (often carbon), the length of time the glass is heated and the temperature that its heated to. that how the glass melts in the muffle – it’s color quality, it’s ability to adhere to the copper in this different environment, the way the particulate from the coal interfered with color clarity. Knowing all this, I thought it might be interesting to show how a given group of enamel colors may appear differently, depending on the heat source.