Clay is a strange substance. When cut from the ground it is easy to shape but when dried in the sun or fired in a kiln it becomes as hard as rock. Its final form, from crude daub to exquisite porcelain, depends on:
• the type of clay
• what the clay is mixed with
• the type and temperature of heating
The geological deposits underlying this area are called the Poole Formation. They contains two types of clay – a brown clay suitable for brick making and a grey clay suitable for pottery manufacture.
The clay trade
To the west of Poole, in the Wareham basin, lies one of the few substantial deposits of “ball clay” in the world. Ball clay has qualities which make it important in the production of white ceramics. Originally it was cut by hand into cubes which, after handling, became rounded into “balls”.
During the industrial revolution, in the 18th and 19th centuries, when Britain became the “workshop of the world”, the pottery towns of the Midlands and Northern England took vast quantities of local clay shipped by barge from Poole Quay.
Josiah Wedgwood signed a contract in 1760 with Thomas Hyde at Arne for the supply of 1,400 tons of ball clay to provide him with his “secret ingredient” to enable him to fire thinner-walled ceramics. Clay continues to be exported from Poole at levels of about 120,000 tons per year. The bulk of the exports goes to Spain and Portugal, with other markets as far away as India and Australia.