|Monthly Tech-Tip |
These are called "Little Dishes" and are sold in tourist areas. They are made in the USA. They appear to be fired at cone 10R (because of the appearance of the glazes and bare clay on the foot). After glaze application and pigment banding, a thick layer of glass powder (glass cullet) is poured in. Since this type of glass has a high CTE it crazes thoroughly during cooling. Of course, that weakens the piece, but since these are decorative the aesthetics are considered more important. This effect can be achieved at any temperature by just using frit powder, Ferro frit 3110 will melt and craze like this at cone 04 or even lower. Suspended bubbles will be a problem, use a firing schedule with a hold to give them time to surface. Also, use a body having low LOI so that it is not generating gas bubbles. Bisque firing pieces at a higher temperature will accomplish the same (for example, if you are making these at cone 04 then bisque fire at cone 03).
Ceramic glazes melt and flow according to their chemistry, particle size and mineralogy. Observing and measuring the nature and amount of flow is important in understanding them.