At cone 03 many terra cottas will fire quite dense and stoneware-like. The lip of the mug on the left is covered with a vitreous white engobe (L3685U) under the glaze (G1916Q). Red bodies are much stronger at low temperatures, but do not lend themselves well to the bright glaze colors that work so well at that range. Putting an engobe on as a base enables decoration with colored slips and a clear over glaze. One caution: The engobe needs to have the same firing shrinkage as the body, to use a vitreous engobe the body needs a frit addition to be vitreous also. If you put a vitreous engobe on a porous earthenware its firing shrinkage will put it under tension and the poor bond with the body will mean quick or eventual failure.
Pages that reference this post in the Digitalfire Reference Database:
This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.