In pottery glazes, minerals are the basis for the glazes as well. They are mixed, or not, and made liquid for dipping or application with a brush. There are many recipes for colors of all kinds. Dangerous metals are no longer used in glazing pottery (i.e. lead) but raku, a very shiny, showy type of glaze is not reccomended for dinnerware or coffee mugs. Some glazes are still somewhat dangerous to potters if care is not taken in the application, but are safe when fired. It is not reccomended that pregnant women glaze pottery. A glaze is a "glassing" of the exterior of the pottery. But, y'all knew that.