Visit to the ceramic department, Via Portuense
The word ceramic comes from the Greek word "κεραμικός" (keramikos), "of pottery" or "for pottery", from "κέραμος" (keramos), "potter's clay, tile, pottery" which is said to derive from the Indo-European word *cheros (unattested), meaning heat . Nowadays the term 'ceramic' indicates the clay after it has been cooked at a very high temperature. Sometimes two or more different kinds of clay are mixed together, adding other mineral substances which gives the different types of ceramic. These materials which are added to a clay body can change and strengthen it. Altering a clay body in this way reduces the shrinkage rate and lessens the degree of stress during drying and firing. Each clay has its own distinct make up, resulting in a different handling quality, colour, temperature range and plasticity or workability. What one sees in the picture on the left is terracotta, i.e, clay which is cooked once (often known as biscuit clay because of its colour) which still has to be varnished.
There are many forming techniques to make ceramics, but one example is slipcasting. This is where liquid clay is poured into a plaster mould. The water in the slip is drawn out of the slip, leaving an inside layer of solid clay. When this is thick enough, the excess slip can be removed from the mould. When dry, the solid clay can then also be removed. The slip used in slip casting is often liquified with a substance that reduces the need for additional water to soften the slip; this prevents excessive shrinkage which occurs when a piece containing a lot of water dries. This kind of technique is used for making lamps, incense burners and larger hollowed pieces.