Duncan Concepts Underglazes CN 253 Black 8 Ounce Bottle Concepts Underglazes formula allows translucent designs with one coat and solid coverage with three. Concepts offer a multitude of vibrant fired ceramic colors in a balanced palette. Compatible hues in light, bright and dark options, make color selection easy. AP Certified Non-Toxic. Food-safe with the application of three solid coats or when food-safe clear glaze is applied. Firing range cone 06 to cone 6. Made in USA.