Bone china

Bone china is a kind of porcelain body first produced in Britain in which calcined ox bone, bone ash, is an essential part. It is distinguish by brilliant whiteness, strength and translucency.

The initial use of bone ash in ceramics is assigned to Thomas Frye in the mid eighteenth century in which he used it to develop a type of soft-paste porcelain. In At the close of the eighteenth century, Josiah Spode carried on with further developments, and duly made it popular, by combining it with kaolin, China stone and china clay to compete with the imported Oriental porcelain.

The initial elemental formula of four parts china stone, six parts bone ash, and three and a half parts china clay remains the standard English body.

Bone china production generally uses a 2 stage firing process where the first "biscuit" is fired without a glaze at 1280°C (2336°F) giving a translucent product and then it is glost, or glaze, fired at a lower temperature below 1080°C (1976°F).

Soft-paste porcelain

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

Its history dates from the first ventures by potters from Europe to imitate Chinese porcelain by using compounds of china clay and ground-up glass (otherwise known as frit); lime and soapstone were known to have also been used in some concoctions. As these initial combinations were prone to high pyroplastic collapse, or slumping in the oven at high temperature, they were uneconomic to manufacture. Compositions were later developed based on feldspars, kaolin, quartz, nepheline syenite and other feldspathic rocks. These were technically superior and continue in production to the present day.

Hard-paste porcelain

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

The secret of its manufacture was unknown in Europe until 1709, when Böttger of Meissen, Germany found the formula. In spite of attempts to keep it secret, the process was taken up by other German ceramic manufacturers and finally became widely used throughout the whole of Europe.

Hard-paste porcelain is known to be fired at a range of temperatures to manufacture a multitude of different end results. Depending on the firing process, hard-paste porcelain can be manufactured to resemble earthenware or stoneware. But mainly, it is not necessary to use hard-paste porcelain for such lower temperature ceramics. Hard-paste porcelain can be utilized to make porcelain bisque, a hard crystalline product fired at very high temperatures in a pressure controlled environment. This technique gives birth to a translucid 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, Precious Moments and Hummel utilize hard-paste porcelain just for this reason.

More about China Replacement Service.