Found this while noodling around in a Pottery Basics Yahoo group.
#1997 Fake Avery Flashing slip opaque white to orange Cone 6 10
15 Newman red or Red Horse clay
1 Soda Ash
Wait, but...Newman Red is a fireclay. Red Horse is an earthenware. How are these interchangeable in this recipe?
Guess I'll have to mix them up and find out.