Rondelay tea saucer

Bone china

Bone china is a kind of porcelain body first developed in the UK in which calcined ox bone, bone ash, is a critical constituent. It is differentiated by extreme whiteness, strength and translucency. rondelay tea saucer may be an example of this process.

The first use of bone ash in ceramics is assigned to Thomas Frye in in the late 1740s in which he used it to introduce a type of soft-paste porcelain. In At the close of the 18th century, Josiah Spode carried on with further developments, and subsequently made it popular, by mixing it with kaolin, china clay and China stone to compete against the imported Oriental porcelain.

The original elementary recipe 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 consistently makes use of a 2 stage firing process where the initial "biscuit" is fired without a glaze at 1280°C (2336°F) giving a translucent product and then it is glaze, or glost, fired at a lower heat under 1080°C (1976°F). rondelay tea saucer is probably made using this approach.

Soft-paste porcelain

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

Its origin dates from the early pursuits by European potters to copy Chinese porcelain by using mixtures of china clay and ground-up glass (aka frit); soapstone and lime were also known to have been added in some formulations. As these first compounds were prone to high pyroplastic collapse, or slumping in the oven at high temperature, they were uneconomic to manufacture. Combinations were later produced based on feldspars, nepheline syenite, kaolin, quartz 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 manufactured from a formulation of the feldspathic rock petuntse and kaolin fired at extremely high temperature. It was first produced in China in around the 9th century.

The secret of its manufacture was unknown in Europe until the early eighteenth century, when Böttger of Meissen, Germany uncovered the formula. Despite attempts to keep it secret, the procedure was taken up by other German ceramic potteries and eventually became known throughout the length and breadth of Europe.

Hard-paste porcelain is known to be fired at a range of temperatures to make a myriad of unique end results. Depending on the firing technique, hard-paste porcelain can be made to resemble stoneware or earthenware. But most of the time, it is unnecessary to utilize 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 method makes 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 decorating. Manufacturers such as Precious Moments, Hummel and Lladro employ hard-paste porcelain simply for this reason, this could include rondelay tea saucer.