Porcelain was so-named after its resemblance to the white, shiny Venus-shell, called in old Italian porcella. The curved shape of the upper
surface of the Venus-shell resembles the curve of a pig's back (Latin porcella, a little pig, a pig).

Properties associated with porcelain include those of low permeability, high strength, hardness, glassiness, durability, whiteness, translucence,
resonance, brittleness, high resistance to the passage of electricity, high resistance to chemical attack, high resistance to thermal shock
and high elasticity.

Porcelain is used to make wares for the table and kitchen, sanitary wares, decorative wares and objects of fine art. Its high resistance to the
passage of electricity makes porcelain an ideal insulating material and it is used in dentistry to make false teeth, caps and crowns.

The earliest porcelains originated in China possibly during the Eastern Han dynasty (25-220 AD).

Scope
Porcelain has many uses but this article is concerned mainly with its employment as a material used to make objects of craft and fine art, including
decorative and utilitarian household wares. Industrial and other uses are not covered here. Another difficult line to draw is that which divides
high-fired stonewares from porcelain. Where this line is drawn depends upon how the terms porcelain and stoneware are defined. In this article
the term porcelain is taken to encompass a broad range of high-fired ceramic wares, including some that might according to some systems of
classification fall into the category of stoneware.
Materials
When referring to the materials that they use, potters often employ words and names in a way that can be confusing for the layman.
Material used to form the body of porcelain wares is often referred to as clay, even though clay minerals might account for only a small proportion
of its whole. The porcelain clay body, unfired or fired, is sometimes spoken of as the paste and porcelain clay is itself sometimes described as the
body (for example, when buying materials a potter might order such an amount of porcelain body from a vendor).

The composition of porcelain is highly variable, but china clay, comprising mainly or in part the platey clay mineral kaolinite is often a significant
component. Other materials mixed with china clay to make porcelain clay have included feldspar, ball-clay, glass, bone ash, steatite, quartz,
petuntse and alabaster.

The clays used by potters are often described as being long or short according to plasticity. Long clays are cohesive (sticky) and of high
plasticity and short clays are less cohesive and are of lower plasticity. In soil mechanics plasticity is determined by measuring the increase
in content of water required to change a clay from a solid state bordering on the plastic, to a plastic state bordering on the liquid, though the
term is also used less formally to describe the facility with which a clay may be worked. Porcelain clays are of lower plasticity (shorter) than
many other clays used for making pottery and wet very quickly, which is to say that small changes in the content of water can produce large
changes in workability. Thus, the range of water contents within which porcelain clays can be worked is very narrow and the loss or gain of
water during storage and throwing or forming must be carefully controlled to keep the clay from becoming too wet or too dry to manipulate.

Some clays used for making ceramic wares are too cohesive to be thrown on the wheel, including for example, the brown clays used to form the
bodies of the red stonewares of Yixing in the Chinese province of Jiangsu and as a result of this Yixing-wares are almost always hand-built.

Methods

Forming Porcelain wares are formed by hand-building, moulding, pressing, slip-casting or by throwing on a potter's wheel. Sometimes a
combination of these methods is used and, for example, it would not be uncommon for a piece to have a thrown body, moulded handles and
slip-cast decoration, the parts being luted together before firing (lute is a thick liquid mixture of clay and water used to join unfired parts together).

The relatively low plasticity of the clays used for making porcelain can cause difficulties for the potter, particularly in the case of
wheel-thrown wares. To the spectator, throwing is often seen as pulling clay upwards and outwards into a required shape and potters often
speak of pulling when forming a piece on a wheel, but the term is misleading, clay in a plastic condition cannot be pulled without breaking.
The process of throwing is in fact one of remarkable complexity. To the casual observer, throwing carried out by an expert potter appears to
be a graceful and almost effortless activity, but this masks the fact that a rotating mass of clay possesses energy and momentum in an abundance
that will, given the slightest mishandling, rapidly cause the workpiece to become uncontrollable.

GLAZING. It is generally supposed that the first glazes to appear on ceramic wares resulted from the unavoidable presence in the kiln of
lime-rich wood ash, which acted on the surface of the wares as a flux. Unlike their lower-fired counterparts, porcelain wares do not need glazing
to render them impermeable to liquids and for the most part are glazed for decorative purposes and to make them resistant to dirt and staining.
Many types of glaze, such as the iron-containing glaze used on the celadon wares of Longquan, were designed specifically for their striking
effects on porcelain.

DECORATIVE. Porcelain wares may be decorated under the glaze, using pigments that include cobalt and copper, or over the glaze using
coloured enamels. In common with many earlier wares, modern porcelain wares are often bisque-fired at around 1000 degrees Celsius, coated
with glaze and then sent for a second glaze-firing at a temperature of about 1300 degrees Celsius, or greater. In an alternative method of
glazing particularly associated with Chinese and early European porcelains the glaze was applied to the unfired body and the two fired together
in a single operation. Wares glazed in this way are described as being green-fired or once-fired.

FIRING. Firing is the operation of heating green (unfired) ceramic wares at high-temperatures in a kiln to make permanent their shapes.

Categories of porcelain
Western porcelain is generally divided into the three main categories of hard-paste, soft-paste and bone china, depending on the composition
of the paste (the paste is the material used to form the body of a piece of porcelain).

Hard paste

One of the earliest European porcelains was produced at the Meissen factory and was componded from china clay kaolin, quartz and alabaster
and was fired at temperatures in excess of 1350-degrees Celsius to produce a porcelain of great hardness and strength. At a later date the
composition of Meissen hard paste was changed and the alabaster was replaced by feldspar, lowering the firing temperature required.
China clay, feldspar and quartz (or other forms of silica) continue to this day to provide the basic ingredients for most continental European
hard paste porcelains.

Soft paste
Its history dates from the early attempts by European potters to replicate Chinese porcelain by using mixtures of china clay and ground-up
glass or frit; soapstone and lime were known to have also been included in some compositions. As these early formulations suffered from high
pyroplastic deformation, or slumping in the kiln at raised temperature, they were uneconomic to produce. Formulations were later developed
based on kaolin, quartz, feldspars, nepheline syenite and other feldspathic rocks. These were technically superior and continue in production.

Bone china
Although orginally developed in England to compete with imported porcelain Bone china is now made worldwide. It has been suggested that
a misunderstanding of an account of porcelain manufacture in China given by a Jesuit missionary was responsible for the first attempts
to use bone-ash as an ingredient of Western porcelain (in China, china clay was sometimes described as forming the bones of the paste,
while the flesh was provided by refined porcelain stone). For what ever reason it was first tried, it was found that when bone-ash was
added to the paste it produced a white, strong, translucent porcelain. Traditionally English bone china was made from two parts of
bone-ash, one part of china clay kaolin and one part of Cornish china stone (a feldspathic rock), although this has largely been replaced
by feldspars from non-UK sources.