Darjeeling

Bone china

Bone china is a kind of porcelain body initially produced in Britain in which calcined ox bone, bone ash, is an essential part. It is distinguish by brilliant whiteness, translucency and strength. darjeeling may be an example of this procedure.

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 type of soft-paste porcelain. In At the close of the eighteenth century, Josiah Spode continued with further developments, and duly popularised it, by mixing it with China stone, kaolin and china clay to compete against the imported Oriental porcelain.

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

Bone china production customarily involves a 2 stage firing 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 heat under 1080°C (1976°F). darjeeling is probably manufactured using this method.

Soft-paste porcelain

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

Its origin dates from the first endeavors by potters from Europe to imitate Chinese porcelain by using combinations of china clay and ground-up glass (otherwise known as frit); lime and soapstone were known to have also been added in some formulations. As these early compounds were prone to high pyroplastic collapse, or slumping in the kiln at raised temperature, they were uneconomic to manufacture. Concoctions were later used based on nepheline syenite, quartz, kaolin, 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Hard-paste porcelain is a hard, dense ceramic that was originally made from a compound of the feldspathic rock petuntse and kaolin fired at very high temperature. It was first produced in China in about the ninth 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 factories and eventually became used throughout the whole of Europe.

Hard-paste porcelain can be fired at a range of temperatures to manufacture many individual end results. Depending on the firing technique, hard-paste porcelain can resemble stoneware or earthenware. Generally however, it is not necessary to use hard-paste porcelain for these lower temperature ceramics. Hard-paste porcelain can be utilized to create porcelain bisque, a hard crystalline product fired at extremely high temperatures in a pressure controlled environment. This approach manufactures a translucid bright white ceramic. Unlike other bisque ceramics, porcelain bisque is almost impermeable by water, therefore it becomes unnecessary to glaze the body before painting. Manufacturers such as Hummel, Precious Moments and Lladro employ hard-paste porcelain exactly for this reason, this could include darjeeling.