Cone 10 Glossy transparent glaze
Recipe
Notes
This is is long-time cone 10 transparent base, it is used by many potters around the world. It was originally employed as a high temperature porcelain insulator glaze on a 25-Porcelain body. It used calcium carbonate to supply the CaO but we converted it to using Wollastonite instead (to reduce surface imperfections and avoid the variations inherent with different supplies of calcium carbonate). Unlike many transparent glazes in use by potters today, this one has a low amount of feldspar to keep the thermal expansion down (and therefore avoid crazing). This glaze also has the correct amount of kaolin, not too high to cause cracking during drying, and no so low that it settles out in the bucket. This recipe is also a good base from which to make a range of different colors and effects (by adding oxides, stains, opacifiers and variegators). The small amount of zinc present is here to get melting started early, it volatilizes at high temperatures. If you are doing fast firing, consider leaving it out (fast fire glazes need to melt as late as possible). For porcelains, use Grolleg Kaolin instead of EPK, the glaze surface will fire bluer and look better. However Grolleg does not suspend it quite as well as EPK, so you may need to add 1% bentonite (or better yet 0.25-0.5% Veegum, it is cleaner). You might also consider switching to a cleaner soda feldspar (or nepheline syenite) to get better melting and an even more brilliant surface (however you may need to adjust it if crazing occurs). If you have crazing issues, it is easy to adjust this recipe to lower its thermal expansion (using Digitalfire Insight or your account at Insight-live.com). The firing schedule is just an example, this will likely work fine with yours.
Description
Reliable widely used glaze for cone 10 porcelains and whitewares. The original recipe was developed from a glaze used for porcelain insulators.