531P
Cone 06-6 underglaze · Goes onto greenware or bisque, bare or under a clear glaze · Opaque with 3 coats, semi-opaque with 2, semi-transparent with 1 · Lead-free and ACMI AP non-toxic, conforms to ASTM D-4236; no lead or cadmium
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A dark teal, near-black where thick.
Spectrum's 500 series is a frit-based underglaze rather than a clay-based one, and that widens what you can do with it: it goes onto greenware or onto bisque, and it can be fired with a clear glaze over it or left bare, where it finishes as a soft matte. Coverage is a matter of coats - semi-transparent at one, semi-opaque at two, opaque at three. It fires cone 06 to cone 6, holds its colour well to cone 6, and many colours in the range stay stable to cone 10; above cone 04 expect small shifts, so fire a test tile before committing a piece. Lead-free, ACMI AP non-toxic and conforms to ASTM D-4236.
