Ceramic colorants that have been fritted in order to eliminate solubility problems and give greater stability in firing and truer color before firing. Most are stable up to cone 5, many to cone 10. Can be mixed with 25—50% Ferro 3134 frit for Maiolica overglaze decoration. Most stains are ground glass and are highly toxic in inhalation.
Mixture of ceramic stains or pure coloring oxides (sometimes with a little flux) in water suspension, which can be used for overglaze brushwork, or as a patina on unglazed clay. Source: Clay: A Studio Handbook