In the past, the main function of most pottery objects was to serve as vessels to cover a number of basic needs: kitchen utensils, preservation of medicines and oils, and even for use in religious practices. Primitive pottery utensils were perfected over the centuries by the great ancient civilisations, and Egyptian, Palestinian and, above all, Greek pottery developed an ornamental style which cannot be considered as a lesser art, but rather as an expression of the culture and art of an entire people.

Types of pottery
Pottery can be divided into two major types: earthenware and stoneware. The first is a porous ceramic usually fired at the lowest temperature of the kiln (900-1,200 �C). Depending on the type of clay used, it takes on either a buff, red, brown or black colour when fired. It needs to be glazed to make it impermeable to water.

Nearly all mediaeval, Middle Eastern and European painted ceramics are of the earthenware type, as is much of the tableware and crockery used in our homes nowadays.

Stoneware, on the other hand, which is water resistant and much more durable, is made by firing clay at a temperature of 1,200-1,280 �C. This gives it a white, buff, grey or red colour and it is glazed only for decorative purposes. Stoneware, which the Chinese made in ancient times, was not heard of in Europe until after the Renaissance.

Preparing and shaping of the clay
The potter usually eliminates some of the impurities found in all clay but coarse matter can also be added in varying quantities to achieve different effects. A certain amount of coarse grain in the clay helps the object maintain its shape during the firing process. That is why potters who use fine grain clay usually combine it with other materials like sand, powdered stone, ground shells or grog (clay which has been fired then ground into coarse powder) before working with it.

Clay�s plasticity allows different methods to be used to shape it. It can be flattened out and then moulded, by pressing it against the inner or outer surface of a mould, which could be made of stone, wicker, clay or plaster. These same materials can be used to pour liquid clay into. A pot, for example, can be shaped using coils of clay: the clay is rolled between the palms of the hands and extended to make long ropes, which are then looped into coils. The shape of the pot can then be formed by placing the coils one on top of the other. It is also possible to take a ball of clay and use your fingers to pinch it into the required shape.

The most complex technique, however, is that of wheel throwing - making a pot on a potter�s wheel. The wheel consists of a flat disk which rotates horizontally on a central spindle. By using both hands, one outside and one inside, a ball of clay placed in the centre of the spinning wheel can be gradually shaped into a pot. Some wheels are turned by a stick which fits into a notch in the wheel, usually operated by an assistant. This is called a handwheel and is the classic wheel used by Japanese potters. In 16th century Europe a flywheel was added which allowed the potter to control the wheel with his or her feet. In the 19th century a kick bar or foot treadle was added and in the 20th century the variable speed electric wheel allowed a better control of the wheel�s speed.

Drying and firing
To prevent the clay form breaking when fired it must first be dried in the air. If the clay is thoroughly dry it can be baked directly on an open fire at a temperature of 650-750 �C. This is the way primitive ceramics used to be fired. Wood fired kilns, and the coal fired, gas and electric kilns which came later, all need to be very carefully regulated to achieve the desired effect when making earthenware or stoneware, since you can get different results by increasing the amount of oxygen in the flames (giving them adequate ventilation to produce a lively flame) or by reducing the oxygen by partially obstructing the kiln�s air inlet.

For example, an iron rich clay will turn red if it is fired in an oxygen rich fire, while in a kiln with reduced oxygen it will turn grey or black. The reason for this is that the red iron oxide in the clay turns into black iron oxide as the clay gives up an atom of oxygen to compensate for the lack of oxygen in the kiln.

Decoration
A pot can be decorated before or after firing. When the clay is half dry and a little hardened, pieces of clay can be embedded into the pot, or lines and patterns can be incised or stamped into it. If the walls of the pot are polished they acquire a uniform finish as the impurities are pushed into the surface and the clay particles are aligned so that the surface becomes shiny and smooth.

Some clays can be polished after firing. Slip, a liquid clay with no coarse particles, is used for this pupose. There are three ways to apply it:
- Once dry, the vessel can be dipped into a creamy slip (which sometimes has colouring added to it).
- It can be brushed on
- It can be poured on with the aid of a spouted can or a syringe.

Underglaze and overglaze decoration
In Neolithic times, ochres and other earth pigments were used on unglazed objects. The metal oxides used in or under glazes needed higher temperatures to fix the colours. The following colours could be obtained from these metal oxides: copper green, cobalt blue, manganese purple and antinomy yellow. If enamels (fine ground pigments applied over a fired glaze) are used the pot should be refired in a muffle kiln with an indirect flame at a low temperature in order to fuse the enamel and glaze.

Transfer decoration consists of printing a design with oxides on paper and, while it is still wet, transferring it to the pot, leaving the paper to burn away in the kiln. This technique is often used for commercially manufactured ceramics. In the 18th century the print plates were hand engraved but now lithography and photography are used.

Ceramics exhibitions
Below are some permanent ceramics exhibitions in Spain:
- C�ntir de Argentona Museum (Barcelona)
�This museum is devoted to collecting, conserving, studying and exhibiting anything to do with vessels for holding water, from whatever geographical area or period, and of whatever type. Their main interest is in the traditional botijo (an earthenware jar for drinking water out of), but they also collect other water related vessels, such as pitchers, water bottles, buckets or pitcher and basin sets, as well as botijos made of non-ceramic materials, such as wood, metal or glass.
- Ollerias Ceramics Museum (�lava)
Most of the items on show have been made in the Pa�s Vasco Piezas workshop although there are some which come from other Spanish potteries. They are classified by uses and functions and are grouped together in different sections: ceramics for cooking; tableware; transport and storage of water; jars for meat curing and food conservation; religious and decorative use; building materials and accessories...
- National Ceramics Museum (Valencia).
It contains interesting and noteworthy ceramic pieces from Manises, Paterna and Alcora.
- Royal Palace of Pedralbes (Barcelona)
In 1919 Count G�ell donated this mansion to the royal family for their sojourns in Barcelona. It is home to a museum of decorative arts and ceramics.
- Cerralbo Museum (Madrid)
This palace-cum-museum has thirty five rooms dedicated to interesting collections of various decorative arts, among which is an outstanding collection of ceramics.