One of the main ways an archeologist can learn about a culture is
through its pottery. A pottery shard found in an archeological
dig can tell the
archeologist what materials were used in a given region, where the pottery clay
came from, what the firing techniques were and the possible cultural purpose
for a given piece.
Pottery is an advanced technology which requires a great deal of processing, experimentation and precision to create. Even using modern pot throwing techniques, molding and hand building (which are similar to their ancient counterparts), the process does not always yield a useable, workable pot. Many times in the process of firing a pot, multiple firings are required which can take days, and this does not include the added complication of glazing techniques. The sophistication needed to create a workable pot, along with the geographical resources needed for clay, has meant that in many areas pottery was not one of the early technologies developed. Many cultural areas within prehistory had a knowledge of pottery, but the more sophisticated forms, such as those found within the South American tribe of the Moche, and within Jamon culture of Japan, display a great knowledge of the medium of clay, and all of its constituent components, which took many years to discover.
Prehistoric pottery techniques generally follow the same principle of firing techniques found today. Clay is gathered from a clay basin or other clay rich area from a given geographical locale. Depending on the clay type, and its elemental properties, the clay is molded and then fired for a certain amount of time in a kiln. Clay types, and the amount of firing needed, vary depending on the level of silica, oxides and other materials found therein as well as the effect the potter wishes to achieve. The predominant material in most clay types and bodies is silica, which has a great deal of plasticity but alone is nearly impossible to work. With the addition of iron oxide, grog, tempering agents, or other elements a wide array of clay bodies are created which can be used for a variety of purposes.
Due to the wide array of clay bodies, most pottery can be categorized into three categories, earthenware, stoneware and porcelain. Earthenware, stoneware and porcelain each have their own specific traits. Earthenware is pottery which has a common use, its texture is slightly gritty until fired, when it becomes semi-porous or biscuit. This semi-porous clay body is then painted with a variety of slips or oxides as decoration. A slip is a mixture of fine clay particles which contain a mixture of oxides as a colorant. The earthenware pot is then fired for a second time, this time the applied slip vitrifies into a glassy layer, covering the pot. The oldest Earthenware pot was recently found at Catalhoyuk, an ancient prehistoric site located in the Mediterranean. As with most firing techniques, the verification process creates a crystalline glassy structure around the clay pot, adding to it’s strength and possible uses.
Stoneware and Porcelain have their origins within ancient China
as early as 1400 BC during the Shang Dynasty. Stoneware pottery is pottery
which is fired at an extremely high temperature of 1200F. The clay body
vitrifies in the firing process, making it impervious to liquids, and sometimes
even to acids. Glazes for stoneware pottery are used on the pots, but only for
decorative purposes. Porcelain is a clay body with relatively few impurities
that, after being fired at between 1400F to 2600F, is virtually transparent.
There are many different varieties of porcelain, however, each behaves in the
same relative way while being worked by the potter. Most porcelains have the
texture of thick butter due to their lack of a tempering material such as grog,
making porcelain pottery a true skill and art form. Porcelain follows the same
basic firing techniques as earthenware, in that it is put into a kiln once, to
become biscuit, a glaze is applied to the pot, and then it is put back into the
kiln once more. Once in the kiln, the glaze and clay body vitrify and fuse
together, creating a strong crystallized glass structure around the pot.
Kiln firing as it pertains to prehistoric technologies only includes earthenware. Native to many areas including the Americas and the Old World, earthenware remained the primary pottery form. Of more importance is the fact that many areas did not immediately discover firing techniques, or pottery techniques for the purpose of food storage or processing. In particular the earliest known firing technique, practiced by Europeans during the ice age, was not to fire their pots, but to sun dry them. Further, cooking with pots was done by placing the coals in the piece of pottery itself, not by putting the food in the pot. To conquer the problem of seepage and solubility in water with pottery, archeological sites have yielded early pots which were baskets lined with clay.
Later in the Bronze Age (1300 BC), pottery was baked on a home hearth, or, through a firing technique known as pit firing. In pit firing a piece is placed into an earthen pit and then the pit is covered with a variety of pot shards. The fire was then built around it, starting with a low temperature and gradually increasing the heat created by the flames. When the maximum heat was reached, the fire was then smothered with ashes and allowed to cool slowly.
The Potters Wheel, Glazes, and Pottery Techniques
Of one of the greatest inventions is the potters wheel.. The origins of the potters wheel remain unknown, but it is estimated to be a technology dating several thousand years old, and is found in Egypt, Greece and many other areas. The earliest potters wheel was a small stand where the clay was fixed in the center, and where the potter would move around slowly forming the clay and painting it as they went. Later the revolving potters wheel grew in popularity. The revolving potters wheel was worked while the potter had one hand on the pot, and another which spun the wheel. Later, the treadle was invented, the treadle allowed for the potter to free both of their hands, and in essence it became what is commonly known today as a kick wheel.
Glazing techniques are also an important tool in the technology of pottery. Pottery covered with hard glazes developed adjunct with glass technology (the earliest glass beads were found in Egypt their date estimated to 3500 BC). Through much experimentation it was discovered by potters, that certain oxides produced certain types of effects on a given piece of pottery. For a glaze to fuse with a given piece of pottery, the glaze must have certain elements which vitrify and are tolerant to the heat of the firing. These elements, known as flux, all fire at different times and temperatures, but make the glaze adhere to the clay body, as well as create the glassy appearance of most stone and porcelain clay bodies. Without a flux and certain other elements in a glaze, the glaze drips off of the clay body at high temperatures and doesn’t adhere.
In addition to glazing and the potters wheel, pot throwing techniques all aided in the creation of modern pottery techniques. These techniques were of three specific varieties, commonly known as hand building, slab, and pot throwing on a potters wheel. Hand building was the mainstay of the prehistoric potter along with slab. With hand building, a piece of clay is kneaded or wedged to the right consistency, and can then be worked into a long piece of round clay. The round piece of clay is then coiled around the base and sides of the pot until finished. Hand building also takes many elements from slab pots. The slab pot technique uses pieces of clay which are wedged and rolled out to a specific thickness. The rolled out clay is then cut and added and the pieces are fused together to make a functional pot.
Wheel thrown pottery is done by placing a piece of clay in the center of the potters wheel. The potter then centers the clay. Once centered, the potter begins to press into the center of the clay. From there, the sides of the pot are pulled up gradually, by a slight pinching action of the hand. When the pot is ready to come off the wheel, the potter cuts it with a wire at it’s base and then is able to take it off. In general, wheel thrown pots can be identified by their dependence on an axis. In addition, all of the techniques above may or may not use elements of each other in the throwing process. For example, a cone shape thrown on a potters wheel can easily be hand built to a pot.
Image of pot courtesy of art123