EARTHENWARE POTTERY MAKING

EARTHENWARE POTTERY MAKING

All the earliest forms of pottery were made from clays that were fired at low temperatures, initially in pit-fires or in open bonfires. They were hand formed and undecorated.

Earthenware can be fired as low as 600 °C and is normally fired below 1200 °C. Because unglazed biscuit earthenware is porous, it has limited utility for the storage of liquids or as tableware.

However, earthenware has had a continuous history from the Neolithic period to today. It can be made from a wide variety of clays, some of which fire to buff, brown or black color, with iron in the constituent minerals resulting in a reddish-brown. Reddish colored varieties are called terracotta, especially when unglazed or used for sculpture.

The development of ceramic glaze made impermeable pottery possible, improving the popularity and practicality of pottery vessels. The addition of decoration has evolved throughout its history.

Stoneware 15th-century Japanese stoneware storage jar, with partial ash glaze
Main article: Stoneware
Stoneware is pottery that has been fired in a kiln at a relatively high temperature, from about 1,100 °C to 1,200 °C, and is stronger and non-porous to liquids. The Chinese, who developed stoneware very early on, classify this together with porcelain as high-fired wares. In contrast, stoneware could only be produced in Europe from the late Middle Ages, as European kilns were less efficient, and the right type of clay less common. It remained a specialty of Germany until the Renaissance. Stoneware is very tough and practical, and much of it has always been utilitarian, for the kitchen or storage rather than the table. But "fine" stoneware has been important in China, Japan, and the West, and continues to be made. Many utilitarian types have also come to be appreciated as art. Porcelain Chantilly porcelain teapot, c. 1730, with chinoiserie decoration in overglaze enamels
Main article: Porcelain
Porcelain is made by heating materials, generally including kaolin, in a kiln to temperatures between 1,200 and 1,400 °C (2,200 and 2,600 °F).
This is higher than used for the other types, and achieving these temperatures was a long struggle, as well as realizing what materials were needed.
The toughness, strength, and translucence of porcelain, relative to other types of pottery, arises mainly from vitrification and the formation of the mineral mullite within the body at these high temperatures. Although porcelain was first made in China, the Chinese traditionally do not recognize it as a distinct category, grouping it with stoneware as "high-fired" ware, as opposed to "low-fired" earthenware. This confuses the issue of when it was first made. A degree of translucency and whiteness was achieved by the Tang dynasty (AD 618–906), and considerable quantities were being exported.
The modern level of whiteness was not reached until much later, in the 14th century. Porcelain was also made in Korea and in Japan from the end of the 16th century after suitable kaolin was located in those countries. It was not made effectively outside East Asia until the 18th century.