Pottery

The pottery indicates at the same time the manufacture of objects out of ground worked and cooked with the furnace, and the objects thus manufactured.

The manufacture of a pottery starts with the mixture of the grounds (Argile, marl, Silice). Then, six techniques are possible to give to the mass the form wished by kneading it.

History

Its invention took place during the Préhistoire: generally, one locates this one at the Neolithic , in Asia Mineure, towards thousand-year-old VIIIe front J. - C. This assumption however is disputed: in Japan, the pottery would have been invented towards thousand-year-old XIe front J. - C. (See the article Jomons). In the Middle East, it would have appeared towards thousand-year-old Xe front J. - C. Another hearth of invention, located in Saharan Africa, as for him was dated from thousand-year-old VIIIe front J. - C. Lastly, of the recent discoveries along the Amur river, in the east of Russia, revealed ceramics traces. These last were gone back to 13.000 front J. - C. and still, their design leaves think that the ceramic traditions would be even older.

With Byblos, the first traces of pottery worked with the hand go back to 4000 av. J. - C.. Between 3500 and 3450 av. J. - C., the pottery undergoes a true revolution with the introduction of the potter's wheel thanks to a new population come from the fertile Croissant. Between 2900 and 2300 av. J. - C., during the Bronze Age, one finds traces of decoration containing Engobe.

The manufacture of white clay parts goes up in China at the beginning of the Dynastie Han, 200 years before the Christian era. At the beginning, the Chinese potters drew from the kaolin of the soft and white pastes. The control of cooking until 1200°C approximately and the white potteries vitrified using pastes mainly made up of kaolin exist in China since at least year 600 of the Christian era. Little by little, they learned how to reach more raised temperatures of cooking and to modify their pastes to obtain hardness, the whiteness and the translucidity of the genuine porcelain. This discovery of the Porcelaine was a technical triumph in the field of the Céramique.

Techniques of shaping

Modelling

Modelling is simply the deformation with the hand of the ground.

Stamping

Small ground balls are applied to or inside an object (water-bottle, old broken pot…) and the ground is then smoothed.

Wad

The wad is a cylinder of ground long and narrow rolled on a table, this wad is then assembled to work out a part. The assembly of several wads is necessary to obtain a part of big size.

This technique is relatively fast and makes it possible to obtain very large parts, completely free forms (technique used by the primitive tribes and the artists ceramists).

The parts carried out with this method are however heavy. The technique can be refined by using a small plank and a roller to compress the ground and to model the shape of the part. The roller is positioned in contact with the ground inside the part and the small plank placed outside on its level makes it possible to type the ground and thus to compress it.

Plate

A ground plate is carried out using a roller (like a Rolling pin) and the various plates are assembled.

This technique is fast, but allows to make only angular parts. One can however obtain cylindrical forms while rolling the plate and by assembling the two opposite ends.

Turning

However, the most sophisticated technique is that of the Tournage. The turn is composed of a rotary table called Girelle. After having laid out a mound of clay with the center of the plate, the potter centers its ground then works it.

Turning makes it possible to obtain only parts of revolution, which can be however deformed then.

These parts are lighter than those obtained by other techniques (except the moulding) but turning requires a prolonged technical training, it is a trade in oneself.

Moulding or casting

The ground is not any more in pasty form, but in liquid form by addition of water and Défloculant. The ground under this state is called the Barbotine.

A plaster mould is used to define the outside of the form, the plaster has as a characteristic to absorb water.

The barbotine is introduced into the mould, and is preserved a few moments.

The water of barbotine is transferred in the plaster, and the density of barbotine will increase near the walls. It should then be waited until the dry casting. The part decreasing of volume (water evaporating), the release from the mould is facilitated.

After having let dry the part long enough to obtain an aspect “leather”, the turner rectifies the imperfections and digs the foot of the pottery; that is called “tournaser” or tournasser. Then, if it is necessary, one passes to the “ansage” (poses handles) and one engraves the part according to the selected model.

It is then necessary to let dry, it is the end of the part “shaping”.

Cooking

For the Cooking, one puts the various parts obtained previously in a Four at a temperature of 850 with 1000°C during approximately 8 hours. One then obtains “cookie” (in the case of the Faïence) or a “bright spark” (sandstone).

The parts can be decorated with the brush using oxides with various colors. The cookie thus decorated, is soaked in baths of enamel.

Once decorated and enamelled, the part is given to the furnace with 960°C during 5 hours for earthenware. The porcelain or enamelled sandstone parts are cooked between 1250 and 1400 °C.

The temperatures of cooking go from 850°C to 1350 °C (and more) according to the nature of the ground used. One distinguishes earthenware, cooked at low temperature (up to 1100°C) of the cooked sandstone at high temperature (up to 1300 °C). Earthenware remains porous after cooking i.e. it can absorb of water and is frost-susceptible contrary to the sandstone which is completely vitrified; like the Porcelain.

If the ground contains many metallic oxides, of alkaline or acid salts, the temperature must be low, if not, the temperature can be increased without risk of fusion.

The pottery is then finished.

See too

  • Reconstitution of pottery mérovingienne: Museum of Cruel Times

Internal bonds

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