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Murrays Borate

Alternate Names: Murray Borate

Oxide Analysis Formula
SiO2 27.80% 0.86
B2O3 36.10% 0.97
Al2O3 0.50% 0.01
Na2O 5.70% 0.17
CaO 24.90% 0.83
LOI 5.00%n/a
Oxide Weight 177.31
Formula Weight 186.64


In 2023 this material is no longer available.

Kickwheel Pottery Supply introduced this material and offered support to users at They had a page with quite a bit of information about how to use it. They claimed it was a frit that had been specially manufactured for this purpose and they assured its continued availability. They recommend the use of bentonite to match the plasticity and outlined how to decide how much to use (as much as 6%). They cited a melting temperature of 1987F (Cone 03) although our flow tests indicate that it actually flows freely as an amber glass at cone 06 (1800F) and melts lower than this.

They did not publish the chemistry on the information page. The chemistry was more different from GB than Laguna Borate, it contained a lot more silica but balanced this with more boron to melt it (greater boron content has implications like lower hardness, less resistance to leaching, color response problems with certain oxides or stains, earlier melting, more crystallization).

Surprisingly, this material produced a lot of gases on decomposition, a bar of it expanded to a bubbly mass many times original size if heated anywhere from 1400-1700F; this was unlike a frit and very unusual. We had reports that this expansion behavior caused some glazes to shed off the ware. This material was analyzed by Mary Simmons as follows: SiO2 27.5, Al2O3 1.6, MgO 1.8, CaO 23.1, Na2O 4.8, K2O 0.1, TiO2 0.05, B2O3 28.6, LOI 12.4. This is quite different from the analysis Kickwheel first cited and the 5% LOI they claimed. This material was a blend of a base frit (prepared by Fusion Ceramics) and likely a significant amount of calcite (the material fizzes when subjected to acid and this explains why it bubbles so much).

Many testers reported on MB and comments from some indicated good success. Comments relating to its lack of plasticity (and therefore ability to suspend) were common, some users reported rock-like settling of the slurry. Others reported that MB is a stronger flux and that glazes tended to run more.

Related Information


Materials Boraq
This Gerstley Borate substitute was available during the early 2000s. Its recipe and development are well documented but two materials are no longer available.
Typecodes Gerstley Borate Substitutes
Many development efforts to create Gerstley Borate substitutes took place during the early 2000s (the initial period when the demise of Gerstley Borate appeared imminent). A number of companies, including Laguna Clays itself, produced and sold these for many years. When Laguna secured another stockpile at the mine and began producing the original material again, interest in substitutes gradually waned. However, the sudden dramatic price increase in 2023 appears to have initiated the process again. Gillespie Borate appears to be the only viable and visible substitute now. Thus, the substitutes listed here are mostly no longer made. Other high-boron materials shown are also no longer available. We continue to recommend sourcing B2O3 from frits instead. Please contact us if you have a specific recipe and we can work with you in your Insight-live account to develop a new recipe that both eliminates the GB and improves overall working and firing properties.
By Tony Hansen
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