Impure clays can be used to make cruder forms of pottery, while kaolin or china clay is needed for finer grades.
Originally a Japanese lead-glazed style of earthenware made during the 16th century in Kyoto for the tea-ceremony, raku ware is traditionally molded by hand instead of using a potter's wheel, and thus each item is unique.
It has been used in the manufacture of pottery since prehistoric times.
Some experts consider that the earliest known fine art ceramic sculpture is the cache of figurines unearthed at Dolni Vestonice in the Czech Republic, as exemplified by the Venus of Dolni Vestonice, a statuette of a nude female figure, which has supposedly been dated to approximately 25,000 BCE.
However, its key characteristic stems from the firing technique used.
While regular earthenware is fired and cooled quite slowly, glazed raku pottery is fired for up to an hour then removed with tongs during its white-heat stage and placed in a cold reduction chamber along with a selection of combustible materials.