Terra Sigillata is the new craze, there is talk about it where ever you look. There are BBS entry's full of questions and information, magazine articles, and plenty of potters trying one or more of the millions of recipes. The technique derived from ancient Greek pottery techniques, dating back to 2500 BC.
The technique of Terra Sigillata, is quite different from glazes common today. Terra Sigillata is a fine solution extracted from the original clay used for the wares, with no additional colorants added.
The method of Terra Sigillata is believed to have been found by accident Greeks. Terra Sigillata can only be made from the finest particles in the clay body. The separation of these particles form the coarser material in the clay was accomplished by sedimentation.
In Medieval times a solution of clay, water and potash were mixed together, and allowed to stand for forty-eight hours. The solution would then separate into three segments. The upper most segment was carefully removed, and then thickened by means of evaporation.
Today, Calgon bath preparation serves as a convenient substitute for potash, as it has similar ingredients. I have also found that the origional Calgon must be used. Today there are many new and diffrent recipies and methods.
When the mixture is applied to the dry green ware, and allowed to dry before firing, it already has a sheen caused by the horizontal alignment of the particles. A luster can be accomplished by polishing. I have seen and tried many different techniques of polishing, but I find that polishing with my bare hand works the best with the Sigillata solution I make. Some say that you can polish with a cloth, a tissue, a plastic grocery store bag, and a chamois.
Partly to economize fuel, ancient Greek pottery was fired only once, but primarily because the Sigillata technique adhered better to an unfired surface.
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