Gerstley borate is a natural material that has been used for decades in ceramics as a flux in low-temperature glazes. Its boron- and calcium-rich composition allows it to lower the melting point of glazes, which facilitates the creation of vitrified and shiny surfaces in pieces fired at moderate temperatures. It is especially valued in transparent glazes and in combinations with metallic oxides to produce vibrant colors and unique decorative effects.
Gerstley borate also acts as a stabilizer that helps prevent problems such as run-off or cracking in glazes. In its natural state, Gerstley borate contains impurities that can contribute to unpredictable decorative effects, such as textures and color variations, making it a popular ingredient in artistic ceramics.
However, its limited availability and variations in its chemical composition have led to the search for modern alternatives, such as synthetic borate blends. Despite this, it remains a popular material in handmade ceramics, especially for decorative and experimental pieces.
Interesting Fact
Gerstley borate comes from mineral deposits in California, where it was first discovered and mined in the 20th century. Its name has become synonymous with low-temperature glazes, and its legacy persists despite challenges in its supply.
Helpful Tip
When working with Gerstley borate, sieve the material carefully to avoid lumps and test in small quantities to adjust its behavior in your glazes. Consider using it in combination with other fluxes to improve the stability and consistency of your mixtures.
