|Monthly Tech-Tip |
Left: Worthington Clear cone 04 glaze (A) uses Gerstley Borate to supply the B2O3 and CaO. Right: A substitute using Ulexite and 12% calcium carbonate (B). The degree of melting is the same but the gassing of the calcium carbonate has disrupted the flow of B. Gerstley Borate gasses also, but does so at a stage in the firing that does not disrupt this recipe. However, as a glaze, B does not gel and produces a clearer glass. A further adjustment to source CaO from non-gassing wollastonite would likely improve it.
In ceramics, calcium carbonate is primarily a source of CaO in raw stoneware and porcelain glazes.
Gerstley Borate was a natural source of boron for ceramic glazes. It was plastic and melted clear at 1750F. Now we need to replace it. How?
A natural source of boron, it melts at a very low temperature to a clear glass.
In ceramic manufacture, knowing about the how and when materials decompose during firing is important in production troubleshooting and optimization