Borax supplies B2O3 and Na2O.
Borax is a highly soluble mineral, formed by the evaporation of ancient lake basins fed by volcanic springs during the Tertiary (26 million years ago) in southern California (Mojave Desert). Asian borax is called by the mineral name Tincal (so is American, depending on who you ask).
Borax is manufactured by U.S Borax and Chemical Corp. and by Kerr Magee Chemical Corp. in California. Borax is a powerful melter in glazes, used in low-fire glazes and as an auxiliary melter in some stoneware glazes. It increases the fluidity of the glaze and helps to heal defects. Amounts up to about 10% may be added to viscous glazes, including high-fire glazes for this purpose. Too much may result in boiling (blisters, and pinholes).
The water content of borax can fluctuate with changes in atmospheric conditions. The water may be driven out by heat; at 735C, all the water is removed (resulting in anhydrous, or fused borax). The 10 water molecules gave rise to the designation 10 Mule Borax (really 10 Mol Borax).
(courtesy of glazy.org)
Responses