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Gerstley Borate: Replacing It in Your Glazes

There is alarm across the ceramic community in North America about the demise of Gerstley Borate (GB). This situation is of interest to people everywhere because it reveals a fundamental change we need to make in the way we view and use materials. I have traveled half way across the continent twice this year pursuing experts and information on this subject and I find this to be a "we didn't appreciate it while we had it" story. However things are working out in such a way that ceramic artists and companies may well be better off than before. Further, the promises of a consistent plastic borate are very compelling, promising to give us stoneware bodies and glazes at lower temperatures than most ever thought possible.

As of the beginning of 2000 US Borax has ceased mining Gerstley Borate. The mining operation was always very small scale and as of late conditions were unsafe and impractical.  Material in the sales channel was predicted to last until the end of the year however a run on remaining stock saw supplies depleted by May. Although often criticized as a variable and undependable material, Gerstley Borate has been tremendously popular in art glazes at all temperature ranges for many decades. The demise of this material has seen replacement efforts that are quite disproportionate to the small amounts that were actually sold. Even US Borax engineers who have long found the material a nuisance are reflecting with interest on the flurry of activity surrounding replacement efforts. Frit manufacturers that barely even knew about Gerstley are duplicating it. In addition I know two engineers at large porcelain plants have worked out a substitute, one of which could be marketed.

Note: We have created the website at http://www.gerstleyborate.com to deal with this issue. Please go there.

If you wish to report on this subject, the following or a paraphrased version could be used:

The past few months has seen a flurry of worldwide discussion on the Internet and activity from vendors and manufacturers to produce substitutes. The efforts seem disproportionate to the comparatively small market for GB (Aunt Matilda uses 2 kg a year). There are about six substitutes available now (one is even from a mineral company in South America) and likely more on the way. We have enough experience with them and by formulating one ourselves that I can say with some certainty that no one is going to be able to produce the perfect match. It is clear that some vendors were rushed to create their products and they have overlooked some minor (and even major) details.

Gerstley Borate has bred a generation of boron saturated glazes that have nice visual character but invariably lack properties like hardness, resistance to leaching, pleasant working properties, and stability. Thus we have some things to learn from this situation. I am convinced that your main tool to deal with this is a knowledge of the options. We have created a web site at http://www.gerstleyborate.com to help you understand what GB was, what the substitutes are, and how this material bred a willful ignorance of material and oxide knowledge in our educational institutions and among potters. The site tells you how to make your own substitute and adjust it for each glaze. It also touches on the technical Nirvana of glazing: How to use INSIGHT software to remove GB on a glaze-by-glaze basis and fix other problems at the same time.