Gillespie Borate provides the same minerals to the glaze as Gerstley Borate creating the same glaze activity, texture and effects. As a carefully manufactured product it provides consistency which was not the case with the variable Gerstley Borate.

Tests have been done in glazes replacing Gerstley Borate on a 1 to 1 basis with Gillespie Borate as suggested by the manufacturer. In some cases the results were very similar. In other cases the Gillespie Borate created more melt making certain glazes run.

We strongly suggest you carefully test this product in your own circumstances.