|Monthly Tech-Tip |
Mitigating factors are poor adherence of the glaze to the smooth-surfaced L4170B terra cotta bisque, high zircon content in the glaze (it reduces melt fluidity) and the very thick application (this is a variation on G1916Q as a majolica glaze). Which is the most important of those factors? The adherence to the bisque. An addition of Veegum CER solved the problem (50g of the solution to 0.75 litres of glaze slurry, with added water to thin it out). Unlike with CMC gum, this slurry still goes on thick and evenly. Although the piece on the left is darker red, that is a photo issue, these were both the same body and fired at cone 04.
Majolica is white opaque glazed red earthenware clay having colored overglaze decoration. But if you know more about what it is technically you will have more control of your product.
Ask yourself the right questions to figure out the real cause of a glaze crawling issue. Deal with the problem, not the symptoms.