Stoneware is a type of ceramic fired at a very high temperature, above 1200-1400 degrees Celsius. The high temperature glazes the clay, so that even in its unglazed state it becomes waterproof. This was a big step forward, as ceramics fired at lower temperatures had to be carefully glazed to guarantee their water resistance. Unglazed stoneware was made in China about 2,000 years ago and invented in Germany in the 13th century, but it was not produced in Britain until the early 17th century.
Stoneware is used for a variety of purposes, including decorative jewelry, figurines and tableware, but it is obviously good for transporting and storing liquids such as beer, wine, vinegar and mineral water. As a result, it was used by grocers, wine and beer merchants, brewers and homeowners to store and sell their products. Not wanting to miss an opportunity to advertise themselves and their products, the names and addresses of merchants were often stamped or transferred to jugs and bottles.
Many of these vessels also bore the maker's seal, in addition to information about their owners, and Bristol was the center of bottle and jug production used by grocers, brewers, and wine merchants. As in many other industries, there were originally several small manufacturers, but by the nineteenth century the industry was dominated by two large companies, Powell and Price.