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( Originally Published 1940 )
Before passing from the early American potters to those who flourished largely after the War for Independence, we can pause to review the actual craft or method of the potter. We might begin this with a reminder that pottery-making is hardly a craft in which we should look for developments or techniques, other than those related to design, which are characteristically American. The origins of the potter's craft are lost in the remotest antiquity. There are ceramic records of races who left their history in no other form. As a craft its antiquity probably rates sec= ond only to that of rock-chipping.
Pottery-making is based upon the two essential facts that clay, when mixed with the proper amount of water, can be easily shaped into almost any form, and that when baked it solidifies into a substance that is hard and resists heat and fracture. Clay is a form of earth that occurs quite commonly in most parts of the world. Its chemical composition varies according to the nature of the finely divided mineral substances that it contains; these are usually hydrous silicates of aluminum, iron, and alkaline salts. The distinguishing quality of clay is the smallness of the particles of which it is composed. In good clay these are not more than five thousandths of a millimeter in diameter. A good clay should also be free from pebbles and humus.
There has always been a mystical and poetical aura around the subject of pottery because of the idea that it is composed of the same substance as Man himself. This theme has appeared widely in "literary" and especially in folk poetry. That it has greatly impressed the potters themselves is evidenced by many such signs as the following characteristic verse on a piece of early Pennsylvania-German slip ware:
"This dish is of earth and clay And men are also thereof."
Or this inscription from an English piece:
"What handycraft can with our art compare For pots are made of what we potters are."
In spite of the prosaic fact that man is not made of clay at all, the mystical halo surrounding the potter's craft goes deeper than substance and is not to be dispelled by chemical analysis. It derives, in fact, from a reverence for the process of creation, which in the case of the potter is unusually intimate, in that he commonly shapes his creations with his bare hands.
The making of pottery entails three or four processes. First is the preparation of the clay; cleaning it, picking out pebbles, grinding, to break it up into its integral particles, and mixing it to the desired consistency with water. Second is the shaping. This may be done by any of three means: by building it up with the unaided hands, by "throwing" it on the potters' wheel, or by forcing it into a mold.
The first method is the most ancient. Primitive men employed several methods. Sometimes they built up their pot in layers, or snake-like spirals, and sometimes they just kneaded it from a simple lump. But while it is not as old as pottery-making itself, the potters' wheel does go back to very early times. The first ones were simply horizontal wheels which the potter turned with one hand while he shaped his clay (on the center of the wheel) with the other. Later a second wheel was attached to the same axle so that it could be turned with the foot, allowing the craftsman the use of both hands on his clay. A great deal later a cord was attached to the lower grooved wheel so that it could be turned by an assistant. This was the method usually employed in early America.
When molds were used they were usually made of plaster-ofparis in two or more parts. The clay was forced into the mold, excess clay cut off with a wire, allowed to set (the plaster-ofparis rapidly absorbing the water), and removed for baking.
The potters' wheel was generally used, the mold serving to shape handles or other attached parts. The motions of the potter's hands on the complacent clay are rhythmic and fascinating to watch, like those of a magician.
After being shaped the piece must be allowed to dry until nearly all of its moisture is gone. Otherwise it will crack in the oven. Then comes the actual baking: the time varying from about fifteen to twenty-four hours for crude earthenware up to three days for very hard stoneware. The ovens used in this country were usually round, with either a round or conical top; the former for common pottery, the latter for hard pottery. The furnace was usually divided like a bee-hive by plates of baked clay, enabling the articles to be placed in separate cells. But in the case of porcelain, and sometimes hard pottery, the ovens were not thus divided. Saggers (or seggars, old spelling) were used. These were circular trays of baked clay, with vertical, perforated rims. The pieces were placed in the saggers, which were then stacked in the oven like pie-plates, one on top of the other, each acting as a cover for the one beneath. The ovens themselves were built of clay with the insides sometimes glazed to prevent particles from falling onto the objects being baked.
After the pottery has been cooled and removed from the oven we have what is known as "biscuit," that is, unglazed pottery. Often this is the finished product. Biscuit is naturally slightly porous, a quality which does not always lessen the value of the ware, according to the purpose for which it has been designed. The ojas of the American Southwest are an instance in which the porosity of biscuit-ware is a definite advantage. These are water jugs, usually of red clay. The clay absorbs a very small quantity of the water which continually evaporates from the surface, thus refrigerating the water.
The purpose of glazing is threefold: to prevent porosity, to resist chemical action, and to decorate. Glaze, as the word implies, is a thin coating of glass applied to the surface of pottery. Sometimes the substance is actually glass to begin with, in a finely powdered state; or the fused components of glass. Sometimes it is merely the alkaline or metallic-salt part of glass, which finds its silica in the clay of the pottery itself.
One way of glazing is to mix the necessary substances with water to a thin consistency and to paint it onto the ware, after which it is placed in the glazing oven until it achieves a complete fusion with the surface of the pottery. In another method, known as "salt glazing" and frequently used on early American stoneware, the process is made part of the original baking. While the ware is at high temperature in the oven, salt is thrown upon it by hand. Most of the salt is converted into a vapor before it strikes the pottery. This produces a fine transparent glaze, characterized by the fact that it is slightly pitted where particles of unconverted salt have struck it.
A glaze may be either transparent or opaque, colored or colorless. In using transparent glazes the decoration, if desired, is applied to the biscuit and is then covered with the clear glaze. In using colored or opaque glaze, the design may be applied in a glaze of two or more colors, or the glaze of one opaque color may be scraped off to reveal the background material in the desired pattern. Glazes are colored by the same means as glass, that is by the addition of metallic oxides, a process the chemistry of which is still as obscure as it was in the 17th century.
The word "slip" in connection with ceramics refers to a very fine grade of clay which is applied to pottery either for decoration or as a corrosion-resistant lining. This "slip" is made by mixing the clay with water to the consistency of cream and usually some coloring substance is added, such as cobalt, to produce blue.
The terms pottery and earthenware are synonymous. They are distinguished from porcelain or china, also synonymous terms, by the fact that they are not transparent or translucent.
Earthenware is divided into "soft-paste" and "hard-paste." Soft-paste is, as one would naturally suppose, softer and more porous. Examination of a fractured edge of this type of ware will reveal separate particles incompletely fused. When touching such a fracture with the tongue the sensation of absorption is perceptible. Examination of a fracture on hard-paste pottery does not reveal separate, unfused particles, nor will it exhibit the phenomenon of absorption to any appreciable degree. Stoneware is a type of hard-paste, glazed earthenware that was extremely popular for practical purposes in early America.
"Slip-ware" is pottery that has been decorated with a slip of one or more contrasting colors by means of the same technique used by bakers in decorating the top of a cake. The cream-thick slip is placed in a funnel with a small hole for its emission and then the craftsman simply "writes" his designs or mottoes onto the body of the ware. This craft was so popular with the Pennsylvania-Germans that many people make the mistake of associating it exclusively with them.
In what is known as "sgraffito ware" an opposite technique is employed. The object of unbaked clay is completely covered with the slip, usually of a much lighter color, and before it has completely dried parts of it are scraped off to reveal the clay beneath in the form of the desired ornamentation or inscription.