Kaolin is the primary material from which porcelain is made, even though clay minerals might account for only a small proportion of the whole.
The word paste is an old term for both the unfired and fired materials.
As these early formulations suffered from high pyroplastic deformation, or slumping in the kiln at high temperatures, they were uneconomic to produce and of low quality.
Formulations were later developed based on kaolin with quartz, feldspars, nepheline syenite or other feldspathic rocks.
Biscuit porcelain is unglazed porcelain treated as a finished product, mostly for figures and sculpture.
Unlike their lower-fired counterparts, porcelain wares do not need glazing to render them impermeable to liquids and for the most part are glazed for decorative purposes and to make them resistant to dirt and staining.
The clays used are often described as being long or short, depending on their plasticity.
) is a ceramic material made by heating materials, generally including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C (2,200 and 2,600 °F).
The toughness, strength, and translucence of porcelain, relative to other types of pottery, arises mainly from vitrification and the formation of the mineral mullite within the body at these high temperatures.
Soapstone and lime were known to have been included in these compositions.
These wares were not yet actual porcelain wares as they were not hard nor vitrified by firing kaolin clay at high temperatures.