Bone china

Bone china is a type of porcelain body initially used in the UK in which calcined ox bone, bone ash, is a critical part. It is distinguish by high whiteness, translucency and strength.

The initial use of bone ash in ceramics is associated with Thomas Frye in seventeen-forty-eight in which he used it to introduce a kind of soft-paste porcelain. In As the eighteenth century drew to a close, Josiah Spode carried on with further developments, and duly popularised it, by mixing it with kaolin, China stone and china clay to compete against the imported Oriental porcelain.

The original elementary recipe of six parts bone ash, three and a half parts china clay, and four parts china stone still remains the standard English body.

The production of bone china mainly uses a two stage firing where the first "biscuit" is fired without a glaze at 1280°C (2336°F) giving a semitransparent product and then it is glost, or glaze, fired at a lower setting under 1080°C (1976°F).

Soft-paste porcelain

Soft-paste porcelain is a kind of porcelain and therefore a ceramic product.

Its history dates from the first struggles by potters from Europe to clone Chinese porcelain by using mixtures of china clay and ground-up glass (also known as frit); lime and soapstone were also known to have been added in some concoctions. As these initial formulations were prone to high pyroplastic deformation, or slumping in the kiln at raised temperature, it was uneconomical to manufacture them. Combinations were later produced based on kaolin, nepheline syenite, quartz, feldspars and other feldspathic rocks. These were technically superior and are still in production to the present day.

Hard-paste porcelain

Hard-paste porcelain is a hard, dense ceramic that was first produced from a composition of the feldspathic rock petuntse and kaolin fired at extremely high temperature. It was first made in China in about the 9th century.

The secret of its manufacture was not known in Europe until the early seventeen hundreds, when Böttger of Meissen, Germany uncovered the formula. In spite of attempts to keep it secret, the procedure was taken up by other German ceramic potteries and finally became well used throughout the whole of Europe.

Hard-paste porcelain is fired at a range of temperatures to make a myriad of unique end results. Depending on the firing method, hard-paste porcelain can be manufactured to resemble earthenware or stoneware. Most of the time however, it is not necessary to make use of hard-paste porcelain for these lower temperature ceramics. Hard-paste porcelain can be used to create porcelain bisque, a hard crystalline material fired at very high temperatures in a pressure controlled environment. This process makes a translucent bright white ceramic. Unlike other bisque ceramics, porcelain bisque is almost inpenetrable by water, therefore it becomes unnecessary to glaze the body before painting. Manufacturers such as Lladro, Hummel and Precious Moments use hard-paste porcelain exactly for this reason.

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