Clay

Clay is very fine particles of dirt which float in a stream or river and then sink to the bottom, where they press on each other and stick together. You generally find clay along the banks of a river or stream, wherever the river is pulling dirt down off the mountains or hills and dropping it in a quiet part of the river lower down. So people who live in river valleys, like the Harappans or the Egyptians, generally can find a lot of clay.

What is so cool about clay (besides that it is easy and cheap to get) is that it is squishy when it is wet, so you can make it any shape you like, and then it dries hard in the sun, pretty fast. If you dry it in the sun you can make it soft again just by throwing it in a bucket of water and waiting a week or two.

But if you put it in a fire, or in an oven (a clay oven is called a kiln) and bake it for a while very hot, the clay is even harder and it will not get soft again even if you put it in water for a long time. This is called firing. People first began to fire clay about 6000 BC.

The most important thing that people in the ancient world did with clay was to build houses out of it by making bricks and drying them in the sun. They mixed straw with the clay to help it stick together better. This is called mud-brick, or adobe (ah-DOUGH-bee), or pise (pea-SAY). Sometimes they fired the bricks, to make them harder and more waterproof.

But people also used fired clay for their dishes and plates and cups and cookpots. People generally fired their roof tiles, which had to be more waterproof than the walls.

And they used it for statues too. The Etruscans in particular are known for their clay statues.

A fired Stone Age vase
from China (Musee Guimet, Paris)

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