Patent ID: 7892997

Claim:
A frit-free, comminuted boron-containing composition for use in glaze production, which composition is obtained by a process which comprises heating to a temperature sufficiently high that calcination occurs but insufficient for the formation of a homogeneous melt a mixture comprising components capable, under the conditions of heating, of forming the oxides B 2 O 3 , SiO 2 , Al 2 O 3 , Na 2 O and optionally CaO in proportions such that the relative percentages by weight of the said oxides, based on the total weight of the said oxides, are as follows: 10 to 18% B 2 O 3 40 to 65% SiO 2 17 to 32% Al 2 O 3 4 to 9% Na 2 O, and 0 to 10% CaO, and then comminuting the resulting composition.