About hard-paste porcelain
Porcelain of the designation hard porcelain is fired at relatively high temperatures between about 1400 and 1460 degrees and differs also in the composition from so-called soft porcelain. The proportion of kaolin is 50 percent or higher. There are also 25 percent quartz and other ingredients, including feldspar. This is responsible for the partial transparency of thin-walled hard porcelain.
Hard porcelain is widely used and, due to the robustness of its glaze and the high strength of the body, is commonly used in gastronomy and households.