Copper red frits and pigments comprising silica and at least one of cupric oxide and cuprous oxide

A method of making a red glass frit pigment composition comprising

• a. smelting a glass by heating a mixture of compounds that provide the following oxides:
• i. 50-75 wt % SiO2,
• ii. 4-22 wt % R2O, wherein R is at least one of Na and K,
• iii. 2-30 wt % R′O, wherein R′ is at least one of Mg, Ca, Sr and Ba,
• iv. 0.5-20 wt % B2O3,
• v. 1-15 wt % SnO, and
• vi. 2-10 wt % of at least one of Cu2O and CuO,
• b. cooling the glass,
• c. annealing, to increase the color strength, if necessary, and
• d. reducing the glass to a desired particle size by mechanical grinding or milling.

A method of manufacturing red glass comprising adding a coloring frit, to a mass of molten colorless glass in a feeder channel, forming glass objects from the molten mass of glass, then subjecting the glass objects to heat treatment so that they develop a red color, wherein the coloring frit is free of lead, cadmium, bismuth, iron, selenium, arsenic, tantalum, chromium and sulfides, and wherein the coloring frit comprises:

• a. 50-75 wt % SiO2,
• b. 4-22 wt % R2O, wherein R is at least one of Na and K,
• c. 2-30 wt % R′O, wherein R′ is at least one of Mg, Ca, Sr and Ba,
• d. 0.5-20 wt % B2O3,
• e. 1-15 wt % SnO, and
• f. 2-10 wt % of at least one of Cu2O and CuO.

A method of decorating a thermoplastic mass, comprising

• a. forming a red-colored enamel composition enamel composition that is free of lead, cadmium, iron, bismuth, selenium, arsenic, tantalum, chromium and sulfides, the composition comprising a solids portion comprising a frit portion, wherein the frit portion comprises, prior to firing:
• b. 50-75 wt % SiO2,
• c. 8-25 wt % R2O, wherein R is at least one of Li, Na and K,
• d. 2-30 wt % R′O, wherein R′ is at least one of Mg, Ca, Sr and Ba,
• e. 1-15 wt % SnO, and
• f. 2-10 wt % of at least one of Cu2O and CuO, and
• g. blending the enamel composition with a thermoplastic mass to form a red-colored thermoplastic mass.