The term ceramics refers to anything that is shaped from wet clay, and then fired in a kiln to make it hard.   There are different consistency's  and colours of clay,  mixed with a variety of other ingredients, produce different types of finished ceramic body, from coarse grain, porous earthenware and the harder stoneware, both referred to as pottery, to the finest porcelain.

The body

Earthenware:

To make it waterproof, earthen ware has to be coated with a glaze. Earthenware clays come in many colours, which can often only be seen if the object has a chip, and the colour can give a clue as to its origins.

Stoneware:

Harder than earthenware, stoneware is also finer textured and non porous even if left unglazed, and could be fired at a higher temperature.  Fine white stoneware was first developed by Staffordshire potters in the early eighteenth century to compete with imported Chinese porcelain.  The white strong clay could be potted very thinly to produce a cream coloured body.  Other fine stoneware's included black basalt and jasper ware.

Porcelain:

First developed in China over a thousand years ago, porcelain can be white, grey or cream.  Objects are strong but delicate and often translucent , hollow pieces usually resonate when tapped..  Its development came from experiments in adding materials such as ground glass, quarts, flint and bones to the clay base.  Soft paste porcelain was made in Europe from the 16th century onwards, and was fired at a lower temperature than hard paste.

Hard paste porcelain originated in china and is water tight even if left unglazed.  It consisted of a mixture of china clay, or kaolin, and a ground felspar mineral called china stone, or petuntse, and the resulting shiny surface is difficult to scratch.  A true porcelain similar to this but creamier was made at meissen in Germany by Bottger 1708 and was first produced in Britain in 1768, using china clay and china stone from Cornwall

The Glaze:  Glaze is a shiny glassy film usually made from materials powdered and mixed with water,  washed over the body to which it fuses during firing. Glazes are used either to make a piece waterproof,  as in the case of earthenware, or for decoration,  they can be matt or shiny, soft or hard, coloured or clear.   Earthenware glazes were based on either tin or lead, while European hard-paste porcelains used glazes based on ground felspar.  A colourless lead glaze was used on early soft paste porcelain, but later a mixture of crushed flint and/or glass was used, known as frit, the three main glazes are as follows:

Lead:  Transparent, glassy, used on most European earthenware.  It can also be coloured by adding metal oxides.  Cream ware, developed by Josiah Wedgwood in the 18th century, is covered in a thin lead glaze.

Tin glaze:  Contains tin oxide, giving the glaze an opaque white finish that could be left plain or decorated with colours.

Salt glaze:  formed by throwing salt into the kiln at about 1300 C during the firing of the stoneware. The sodium in the salt combined with silicates in the body to form a thick glassy glaze. English salt glaze from the mid 18 century is light buff in colour with a dimpled orange peeled surface.

The Surface:
The surface of pottery often has distinctive characteristics:

Crackling: the surface of lead glazed wares often feature a network pattern, owing to the fact that the glaze does not form a natural bond with the body and also has cooled at a different rate, causing the surface to crackle.

Iridescence: The lead glaze is prone to breakdown over time into layers, giving a rainbow effect.

Pinholes: small bubbles sometimes produce small holes in the glaze, this can be caused by variations in thickness of the glaze.

Decoration:  It is sometimes difficult to tell between transfer print and painting on ceramics, but if examined closely with experience it becomes easier to tell the difference.  For instance, shading that has been painted on to an object will be colour washed, while a transfer print  will be cross hatched,  vertical lines on a printed object are straight, where the artist will have more of a flow with freehand brush strokes.

Although few pieces would be signed, some factories added a code to their own mark  to tell who painted the item

Under glazed colours, known as high temperature colours, are able to withstand  a temperature of 1300C.  The colours are usually antimony (yellow) iron (brown), magnesia (purple) and copper (green).

Over-glazed enamels fired at a lower temperature of up to 950C, give a much greater range.  Enamel colours where made by adding metallic oxides to molten glass and reducing the cooled mixture to a fine powder.  This is then mixed with an oily base, painted onto the surface then fused by firing.

Moulding and Casting:  Most ceramics figures where reproduced in quantities ranging from ten to thousands, using moulds made from an original model.  Clay pressed into the mould was left to harden before the figure was freed and fired.   To make more complex forms with bold or undercut detail, parts of the figure or vessel would be made in separate moulds then put together with slip.  Heavy , almost solid pieces where made with this method.

Many factories  used moulds made from plaster of Paris from 1720, liquid clay was poured into the mould and left to stand, the water was absorbed leaving the clay to harden in the mould then the figure or vessel would be removed