Different Names For Pottery Clays
These different names for clays are indicative of their uses, origins and appearance, and each fits into one of the above three categories of pottery clay. For example, iron oxide (rust) makes a red pottery clay, sometimes known as 'terracotta’ and normally refers to red earthenware.
Kaolin is another word for china clay which is an essential for the manufacture of porcelain and bone china (a type of porcelain with bone ash added). As a general rule, the more impure the clay, the more coarse its end product will be (e.g. bricks). Conversely, the finer the material, the finer the product (expensive tea services etc). China clay is found in great quantities in Cornwall, England and also Malaysia.
Feldspar clay (aka petunse or petuntse), is the aluminum silicate component of porcelain. It vitrifies to give the translucent glass-like appearance of porcelain. Feldspar was referred to by the ancient Chinese makers as the ‘flesh’ of the pottery clay. Although for years was the missing ingredient the Chinese kept from the European makers, feldspars can be found in many types of sedimentary rock the world over. Petunse or petuntse was the original mineral in which it was found.