About eighty percent of the earth’s crust is clay.
Some clays were formed about 300 million years ago when the earth was cooling; others are much younger, only about 35 million years old, and were formed by the decomposition of other rocks and deposited, away from their forming grounds by rivers and through natural erosion.
Clays come in all kinds of colors from white ( china clay) to black ( ball clay). Potters and cay modelers often use red clay ( which is really brown) and which fires to the pinkish red color of bricks and plant pots, or they use a grey clay, which fires to a buff color.
Clay is indeed a very versatile material. At the one extreme we can mix it with water and use it as a liquid, called slip. This can either be painted on to pots as decoration, or poured into moulds for casting. It then dries and takes the shape of whatever is being used as a mould. Many of our tablewares are made that way. At the other extreme clay can be dry and hard and can be used for bricks, either baked in a kiln or oven or, in hot countries, just dried in the sun. In between, clay can be cheese- or leather- hard, ideal for carving like soap or wax. Or it can be plastic and kneadable, like dough, when it will readily respond to the touch.
Although you cannot possibly dig your own clay all the time, you should have some experience of taking clay from the earth, or seeing it extracted. There is so much earth-moving and building work in progress nowadays that it should be possible to find some clay being exposed. Or perhaps there is a brickworks nearby, or a works making drainpipes, or chimney pots, or sanitary ware. You could probably buy some clay at these works and be shown how it is mixed.
Clay can come in many conditions from liquid clay to bone dry rock. If wet it can be dried, and if dry it can be made wet again. But once fired, it changes its nature completely. It will not return to clay. It can be smashed and buried, but not destroyed; it is one of the most imperishable materials that man has ever worked. When things made of wood, fabric, leather and iron have long since rotted or rusted away, pots remain. Much of what we know of civilizations long gone, has been pieced together by archaeologists from fragments of pot which have endured for centuries after the men who made them, and the cities they lived in, have disappeared.
Man was making things of clay before he could write, and one of the first things he wrote on was a clay tablet. No other earth material has so wide an importance or such extended uses as clay. Sunbaked bricks, clay drainpipes made in the valleys of the Tigris and the Euphrates up to 6000 years ago, are our first evidence of industrial clay work. Ramesses II, the Egyptian Pharaoh of 1300 BC, adorned the walls of his palace with highly decorated tiles. By 1000 BC, the Greeks had socketed, jointed drainpipes and the Cretans terra cotta drains.
Clay has many more uses today. It is used in cosmetics and as a filler in paper making. The huge insulators on the pylons of the Central Electricity Generating Board are made of clay and so are the tiny inner parts of the electrical switches and sockets in our homes. Washbasins, cups and saucers and jugs , tiles and toilets , are all made of clay.
It is a basic human experience to model and mould and shape things in the hand. We play with mud and sand as children- but clay holds its shape better than either of these and is the ideal material for this experience. Clay is easily shaped by pushing, pinching, adding or cutting away. This freedom has its disadvantages . The limitations imposed by materials like wood and metal can be of use to the artist- they have their own form and nature. Clay responds so readily that it is more difficult to realize its limitations and potentialities. We can shape it without tools and with very little skill to begin with, but with increasing awareness of what clay will do, our skill in the use of it will increase.