A cure for long-time Gerstley Borate sufferers


Wednesday 24th June 2015

These are various different terra cotta clays fired to cone 04 with a recipe I developed that sources the same chemistry as the popular Worthington clear (50:30:20 GB:Kaolin:Silica) but from a different set of materials. They key change was that instead of getting the B2O3 from Gerstley Borate I sourced it first from Ulexite (G2931B) and then from a mix of frits (G2931K). All pieces were fired with a drop-and-hold firing schedule (like C03DRH). Fit was good on many terra cottas I tried (pieces even surviving boiling:icewater stressing). Where it did not fit I had thermal expansion adjustability because more than one frit was sourcing the boron. Frits are so much better for sourcing B2O3 than Gerstley Borate (the later is notorious for turning glaze slurries into jelly!).

Pages that reference this post in the Digitalfire Reference Database:

Ulexite, Gerstley Borate, Help for Long-time Gerstley Borate Sufferers!


This post is one of thousands found in the Digitalfire Reference Database. Most are part of a timeline maintained by Tony Hansen. You can search that timeline on the home page of digitalfire.com.