Earthenware, one of mankind's oldest inventions, has been gradually refined over the last 500 years to become a versatile, practical and often highly decorative material.
Earthenware is a name given to anything made of moulded, baked clay. In its natural state, it's porous, and has to be glazed if anything liquid is to be kept in it.
Types of earthenware are generally named for the different kinds of glazes, though in some, notably stoneware, a different manufacturing process is used.
Basic, unglazed earthenware, or biscuit varies from pale buff, through brown to red, depending on the clay.
Early earthenware was sometimes decorated with slip, a watery solution of white or coloured clay. Sometimes this was trailed on, and sometimes, when it was used more thickly, it was moulded and applied to the pot.
The technique was known in Roman Britain, but was reintroduced to the country only in the 17th century.
In the same century, cobalt oxide and a glaze of silica, lead and tin combined to create a blue and white painted decoration, known as Delftware. This was fragile, and most surviving examples are chipped.
This couldn't be said of the brown and red stoneware produced later in the 17th century. Stoneware is made in kilns heated to 13000C. At this heat, clay bakes to a stronger, nonporous material. Potters threw handfuls of common salt into the kiln. This vaporized to produce a thin, transparent glaze.
The next innovation was the introduction of creamware in the first half of the 18th century. Refined clay and calcined flint, baked at lower temperatures, produced an attractive, pale cream-coloured ware that was given a colourless glaze.
By the end of the 18th century, enamelled colour was increasingly used. Moulded earthenware figures were made, as well as domestic wares such as jugs and caddies. At first, the colour range was dominated by ochre, blue and green: yellow, black and brown were seen less often.
In 1800, the Turner brothers of Staffordshire patented stone china, where felspar was included in the clay to create a heavy earthenware with a superficial resemblance to porcelain. It was typically used to make tea, dinner and breakfast services.
Through the rest of the 19th century, factories refined production techniques to produce even more colours and decorative finishes on earthenware, and the art potters who worked later in the century were able to call upon a wide range of new techniques, as well as old and traditional ones, to create their wares.