|Monthly Tech-Tip |
Often potters just abandon a glaze recipe when encountering a problem like this. But it is often better to make adjustments to a recipe that has otherwise proven valuable. In this case, the user was firing at cone 5 because the porcelain plates were warping at cone 6. Spraying was being done using a dipping glaze have a specific gravity of 1.47 - there was no gum addition to enable the laydown to flatten out during drying. The user was advised to try the G2934Y recipe instead, use all raw kaolin (instead of a calcine:raw mix) with an addition of CMC gum. With enough CMC gum brush application is also possible, it can give very good control of laydown. For pieces being dipped we advised a specific gravity of 1.44 with enough Epsom Salts added to create a thixotropic slurry.
G2934 - Matte Glaze Base for Cone 6
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte.