York tea coffee saucer demitasse

Bone china

Bone china is a kind of porcelain body originally produced in the United Kingdom in which calcined ox bone, bone ash, is an essential part. It is characterised by high whiteness, strength and translucency. york tea coffee saucer/demitasse 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 develop a type of soft-paste porcelain. In At the close of the eighteenth century, Josiah Spode continued with further developments, and consequently popularized it, by combining it with china clay, kaolin and China stone to compete with the imported Oriental porcelain.

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

The manufacture of bone china customarily makes use of a 2 stage firing process where the initial "biscuit" is fired without a glaze at 1280°C (2336°F) giving a semiopaque product and then it is glost, or glaze, fired at a lower setting under 1080°C (1976°F). york tea coffee saucer/demitasse is probably produced using this approach.

Soft-paste porcelain

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

Its history dates from the initial struggles by European potters to replicate Chinese porcelain by using compositions of china clay and ground-up glass (otherwise known as frit); lime and soapstone were also known to have been used in some mixtures. As these early combinations suffered from high pyroplastic collapse, or slumping in the oven at raised temperature, it was uneconomical to produce them. Concoctions were later developed based on nepheline syenite, feldspars, 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 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 ninth century.

The secret of its manufacture was not known in Europe until 1709, when Böttger of Meissen, Germany found the formula. Despite attempts to keep it secret, the procedure was employed by other German ceramic factories and finally became used throughout Europe.

Hard-paste porcelain is known to be fired at a range of temperatures to make a multitude of different end results. Depending on the firing technique, hard-paste porcelain can resemble stoneware or earthenware. Mainly however, it is not necessary to use hard-paste porcelain for such lower temperature ceramics. Hard-paste porcelain can be used to create porcelain bisque, a hard crystalline product fired at very high temperatures in a pressure controlled environment. This process manufactures 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, Hummel and Precious Moments utilize hard-paste porcelain simply for this reason, this could include york tea coffee saucer/demitasse.