The Craft of Athenian Pottery / An Investigation of the Technique of Black-Figured and Red-Figured Athenian Vases

by Gisela M. A. Richter

PREPARATION OF THE CLAY

Ingredients and properties.

The making of a pot begins in the clay bed. The clay has to be found, it has to be transported, and above all it has to be tested to see whether it is adapted to the potter’s needs. For there are many different kinds of clay and they are as individual as human beings; so that a thorough understanding of them is essential to the successful potter.

The chief ingredients of clay are silica, alumina, and water. Other possible ingredients are iron oxide, lime (calcium oxide), magnesia, and potash. To the iron compounds are due the different colors of the clay. When potters speak of the color of a clay—red, yellow, white—they refer to the color after burning, not in the raw state. The tones of the color are controlled by heat; for instance, a red clay becomes first pink, then in a higher fire a deeper red, and in a still higher fire a brownish red.

The potter demands three properties of his clay: (1) plasticity, the property which enables the clay to acquire form; (2) porosity, the property which enables the water to escape; and (3) vitrification, the property which enables the clay to be fired. These three properties are due to the three chief component parts of the clay; namely, clay base, quartz, and feldspar. It will be found that some clays are not plastic enough, others not sufficiently porous, and others again not properly vitrifiable; in such cases the addition of certain substances is necessary to make the clay usable. The actual composition of the clay, therefore, is of great importance, as no amount of skilful labor will avail if the clay itself has not the right consistency.

Washing.

When the right composition of the clay has been assured, the next step is to wash it and separate it from the many natural impurities, such as stones, sticks, etc., with which it is mixed. A clay not properly washed is a source of great vexation in the later stages of pottery making. The best method is that of “blunging,” that is, the dry clay is put into water and stirred constantly until it reaches the consistency of cream, technically called “slip,” whereupon it is poured through sieves, coarse or fine according to the desired consistency. The liquid clay or slip must then be dried sufficiently to become plastic and workable. This can be done either in filter presses in which the water is squeezed out in a comparatively short time, or in shallow receptacles in the open air where the water is allowed slowly to evaporate.

Wedging.

But even at this stage the clay is not yet ready for use; it has first to go through the important process of kneading or “wedging.” This consists of cutting a ball of clay in two against a wire (fig. [1]), slapping the two parts on a plaster or wooden board, one on top of the other (fig. [2]), then lifting up the whole lump, cutting it in two again, and slapping it down as before. The purpose is to remove all air bubbles and to correct irregularities in hardness. The operation has sometimes to be repeated fifteen or twenty times before a good texture is secured.[5]

Fig. 1. Wedging (a)

We learn from the above survey that the fine consistency of the clay in Athenian and in some other Greek wares is not necessarily due to its natural state, but to the careful washing and kneading undergone in its preparation for use. When different particles are found in the fired clay they are due to indifferent washing. And the varying shades of pink and red of Greek vases likewise do not presuppose different kinds of clay, but are due largely to the various temperatures to which the vases were fired. We have too often made our analyses of clays of Greek vases without due cognizance of these facts.