A medium to hard unleaded frit.
Similar to borax frits, alkaline frits are noted for their high soda and potash content. The colour response from copper and manganese is turquoise and purple/brown respectively – typical of this type of frit. Alkaline frits have a high expansion rate which makes them a suitable base for crackle glazes.
A frit is a type of ceramic glass. It is a combination of materials that, when melted together, are rendered insoluble and resistant to acid attack. They are, therefore, a means of introducing certain materials into a glaze which would otherwise be toxic. Frits can be used alone as low temperature glazes, e.g. raku and majolica, but generally they form the basis of a glaze recipe.