I remember the topic coming up class last week about the use of burnt materials in creating designs on ceramic pots. I did some research and found a name and some methods/guidelines for creating pots in this style.
The style is a western interpretation of an ancient japanese style of pottery, raku, which involves firing to lower temperatures, then removing the still glowing piece from the kiln to be further treated. According to wikipedia, stoneware is bisque fired to 900 degrees Celsius then place in a hot cone 6 kiln, about 800-1000 degrees Celsius, for an hour or two. They are then removed from the kiln for further treatment.
In traditional raku, the piece is glazed normally, fired as raku, then removed and either oxidized or reduced. In horsehair raku, the piece is unglazed and raku fired. When removed, carbon based substances, such as hair, sugar, or feathers, are placed over the still hot pot, causing them to burn into the surface of the clay. When the pot cools, it is given a wax finish. If the clay body is strong enough, and resistant to thermal expansion, it can be placed back in the kiln again. I'm curious as to wether re-firing a raku pot would allow for the use of a glaze after burning designs on.