Yorktown covered vegetable dish

Bone china

Bone china is a kind of porcelain body initially developed in the United Kingdom in which calcined ox bone, bone ash, is a major constituent. It is differentiated by high whiteness, translucency and strength. yorktown covered vegetable dish may be an example of this process.

The initial use of bone ash in ceramics is credited to Thomas Frye in in the late 1740s in which he used it to develop a type of soft-paste porcelain. In As the 18th century drew to a close, Josiah Spode continued with further developments, and subsequently popularized it, by combining it with China stone, kaolin and china clay to compete with the imported Oriental porcelain.

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

The manufacture of bone china routinely employs a two stage firing process where the first "biscuit" is fired without a glaze at 1280°C (2336°F) giving a semiopaque product and then it is glaze, or glost, fired at a lower setting less than 1080°C (1976°F). yorktown covered vegetable dish is probably produced using this process.

Soft-paste porcelain

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

Its history dates from the initial endeavors by potters from Europe to replicate Chinese porcelain by employing combinations of china clay and frit or ground-up glass; lime and soapstone were known to have also been included in some mixtures. As these first compositions suffered from high pyroplastic deformation, or slumping in the kiln at high temperature, they were not economical to manufacture. Formulations were later produced based on quartz, kaolin, feldspars, nepheline syenite and other feldspathic rocks. These were technically superior and are still in production to this day.

Hard-paste porcelain

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

The secret of its manufacture was unknown in Europe until the early seventeen hundreds, when Böttger of Meissen, Germany discovered the formula. In spite of attempts to keep it secret, the procedure was employed by other German ceramic potteries and eventually became known throughout the length and breadth of Europe.

Hard-paste porcelain can be fired at a range of temperatures to make many different end results. Depending on the firing method, hard-paste porcelain can resemble stoneware or earthenware. Most of the time however, it is not necessary to use hard-paste porcelain for these lower temperature ceramics. Hard-paste porcelain can be employed to manufacture porcelain bisque, a hard crystalline material fired at extremely high temperatures in a pressure controlled environment. This technique produces a semitransparent bright white ceramic. Unlike other bisque ceramics, porcelain bisque is almost impermeable by water, making it unnecessary to glaze the body before decorating. Manufacturers such as Lladro, Precious Moments and Hummel employ hard-paste porcelain exactly for this reason, this could include yorktown covered vegetable dish.