On Zero3 porcelain. Between 10 and 15% stain with 2-3% zircon added (to prevent bubbling). The firing schedule approached cone 03 (1950F) at 100F/hr for the final 100 degrees, held for 5 minutes, dropped to 1800 and held for 30 minutes.
G2931K - Low Fire Fritted Zero3 Transparent Glaze
A cone 04-02 clear glaze developed from Zero3 which in turn was developed from Worthington Clear. This employs frit instead of Ulexite.
This is a type of stain manufacture that enables the use of metal oxides (like cadmium) under temperature conditions in which they would normally fail.