TEHRAN Pottery is a general term for all wares made of clay and hardened either in the sun, in a fire, or in some kind of kiln. Kilning has for centuries been the customary method, although the other two proceeded it and are still employed among primitive peoples. Clay occurs in nearly every part of the world inhabited by man, much of it in easily accessible places, such as hill-sides and the banks of streams and rivers.

It is of two main types: sedimentary, clay which has picked up all kinds of sediments and other materials while being transported by streams; and residual, clay that has resided in one pocket since it was first formed and therefore is in its original pure state. Sedimentary clay is the more common and more useful to the potter. The type of sediment in any clay influences its behavior both in handling and in firing.

Clays that have a high iron content turn red or pink in the kiln; others turn buff, gray-blue, brown, pink, or black. Although too brittle for most potting purposes, residual clay, which turns white on firing, has been used for decoration since the earliest times. The degree of heat reached in the firing and the amount of air accompanying it also affect the appearance and substance of the finished ware.

All these factors were observed and made use of long before the geology of the world and the chemistry of clays were understood. Cooking and storage pots, eating and drinking vessels, and urns for the cremated remains of the dead are the earliest-known pottery vessels. From the aspect of these wares we may imagine that common clay was cleaned of foreign bodies, such as roots and stones, and potted into slabs or rolls that were then used to build up the required shapes by hand.

While the clay was still soft, patterns were made on the wares with the finger or a pointed stick, and they were then placed in an open wood fire to harden. The important contribution to ceramic history made by Persia between the 10th and 14th centuries A.D. was made possible largely by the tradition of potting and knowledge of glazes preserved in the region from its remotest age.

Not only were the Persians supreme in shaping claywares into beautiful, serene shapes; they also had two means of producing a white surface on which colored designs could be painted, regardless of the color of the clay body underneath. The first of these was to coat a finished vessel with a white slip of white-burning pipe clay, on the absorbent surface of which designs were painted with a sure touch and covered with a clear alkaline glaze.

The second process was to cover the clay body with a glaze that was opaque and white by the addition of tin oxide. The surface was then painted with colored enamels that were no more than clear glazes tinted with metal oxides. The former method was the more common, since tin was a rare and costly material in Persia. Painting in luster colors was also first practiced in Persia. Silver and copper, sometimes with a small addition of gold, were ground up and the resulting powder suspended in a liquid that was then used to paint designs on a white surface.

The powder on firing turned either brownish-olive, coppery, or, in alight firing, golden. Calligraphic, abstract, and plant designs were executed in both colored and luster decoration. Wall tiles for mosques were commonly decorated with luster, as were dishes and jugs. Pottery is a self-reflective industry, whose finished product is totally different from the raw material. On pottery Sir H. Read said: Pottery is the most simple and the most difficult art.

It is simple because the primitive people practiced it and it is difficult, because it is the most abstract art. In its pure state the art of pottery is visual. In comparison with other arts, it gives further chance for the artist to shape his personality. Pre-historic pottery works of Gilan, are the most beautiful works in the field. The quality of clay in the region is the main factor for high quality of the pottery wares there.

The art, once feared to be fading, is now coming up. The flourishing industry is now capturing minds, transcending borders.