Gerstley Borate 1kg
G.B. is an inexpensive source of B2O3 and CaO in glazes. It is often used in place of colemanite. The primary differences are:
- Colemanite contains a higher concentration of B2O3,
- G.B. contains Na2O, which may affect the color and surface of some glazes, and
- the Bentonite component of G.B. - up to 18% - significantly affects the properties of the raw glaze. (Some other sources indicate that this is not bentonite, but rather shale. GB glazes do tend to gel in either case.)
