Come and visit us in our shop near Portobello

Gerstley Borate

£11.35 GBP

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:

  1. Colemanite contains a higher concentration of B2O3,
  2. G.B. contains Na2O, which may affect the color and surface of some glazes, and
  3. 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.)