A high-temperature, iron-rich clay coating designed for application to ceramic forms and fired to cone 10 (approximately 2345F or 1285C) that results in a deep, often glossy, black surface. This coating, known for its opacity and rich color development at high temperatures, is applied to bisque-fired clay bodies before the final firing.
The application of this type of coating provides an aesthetic depth and sophistication to ceramic work. Its deep color can enhance the form of a piece, highlighting contours and textures. Historically, such coatings have been utilized to mimic the appearance of more precious materials or to provide a durable, functional surface to utilitarian pottery.