Pottery Analysis
Pottery Analysis
Typological analysis and other dating techniques
Man first began making pots at the end of the Stone Age (Neolithic Period), about 12,000 years ago in the Old World, and about 5,000 years ago in the New World.
By about 6500 BC, hunting and foraging had largely been abandoned in Old World Neolithic agricultural villages. The need for pottery arose during the change-over from a food-gathering to a food-producing economy. The cultivation of grain required that man be able to store cereals for future use. But pottery was also used for carrying water, for cooking, and for serving food.
Basketry, including clay-lined baskets, probably served adequately for food storage for awhile. It may have been the accidental burning of a clay-lined basket that led to the discovery that clay, which is malleable when wet, becomes hard and brittle when burned. Further experimentation would have revealed that the piece of burnt clay could be subjected to additional heat without causing the object to disintegrate, which made it suitable for cooking vessels. The manufacture and firing of pottery represented an adaptation of fire-based technology, which was later to evolve into furnace-based metallurgy.
The earliest pots were made by hand, either by being molded or by being built up. Although small pots could be molded, larger ones had to built up by placing successive rings of clay on top of each other.
With the invention of the potter’s wheel, probably in the area of the Fertile Crescent, large vessels could be constructed in a few minutes, rather than several days. Until the invention of this device, women tended to be responsible for creating pottery; with its invention, pottery entered the domain of men.
Even the earliest pots appear to have been decorated. Decorations have ranged from simple geometric patterns to the elaborate illustrations characteristic of Chinese vases. Some early examples appear to have been made in imitation of baskets, or to have been molded inside a basket. Patterns on pots were probably created with finger nails, pointed sticks, or bird bones.
The art of pottery requires just the right material, i.e., the clay starting material must be neither too gritty nor too fine in texture. And the wet clay object must not be allowed to dry out before it is fired. Finally, the temperature of the firing oven must reach a critical value if the fired object is to retain its shape permanently. These discoveries may have occurred in the period of the Stone Age just preceding the Neolithic Period (that is, the Mesolithic Period), becoming universal in the Neolithic period. Pots or potsherds are frequently found in the ruins of Neolithic cultures.
Each culture evolved its own unique form of pottery. These shapes typically developed into characteristic forms that changed little over time. In addition, buried pottery does not deteriorate with time. As a result, pottery has become one of the best resources for dating an archeological site. Even if pots have become broken, the potsherds can still be pieced together into their original form. This of course cannot be done with objects of wood, leather, skins, or cloth.
The presence of pots at an archeological site may reveal information about contacts that once existed between prehistoric cultures, or about trade routes in later civilizations. Pottery exported from Crete in the eighteenth century BC, for example, has been found on the mainland of Greece, on Cyprus and on other islands in the Aegean Sea, on the coast of Syria, and in Egypt. Other discoveries have shown that by 400 BC, Greek vases were being exported to the steppes of southern Russia, southern Germany, and northern France. The shape, size, type of clay, type of temper, surface treatment, and painting that characterize an ancient pot all provide valuable clues to the archeologist seeking to date an artifact or site.
Pottery analysis
Archeologists typically perform four types of analysis on ceramic artifacts: experimental studies, form and function analysis, stylistic analysis, and technological analysis. In experimental studies, archeologists attempt to replicate ancient methods of pottery making in the laboratory. These studies yield valuable information about firing techniques, firing temperatures, and about the properties of coating materials. Archeologists may also study present-day pottery-making techniques in various cultures around the world to better understand how methods were used by traditional cultures.
Analyses based on form and function focus on the shapes of ceramic vessels. The underlying assumption in this approach is that the shape of the vessel was determined by the way it was used. One weakness of this approach is that it ignores other factors that may have influenced the shape the object took, such as the material properties of the clay used, the manufacturing technologies available to the potter, and any cultural factors that might have constrained the form that the vessel eventually took. When employed properly, form and function analyses can provide valuable information about ancient economic patterns, units of measure, household food production and consumption, and household sizes.
Stylistic analysis focuses on the decorative styles applied to ceramic artifacts, including painted designs, incisions, embossing, and other surface treatments. Because decorative patterns, and the information they convey, are more likely to have been determined by specific cultural elements than are form and function, stylistic analysis is the technique most frequently used to analyze ancient pottery. When the results of stylistic analyses are validated against other archeological data, it often becomes possible to trace social change in a culture through time. While there is no doubt that this type of analysis has made great contributions to archeology, there remains a need for greater rigor and consistency when applying it across different regions and time periods.
Technological analyses look at the materials from which the ceramic is made. Of chief interest are the chemical composition of the clay, the tempering materials, and the proportion of clay to temper. Technological analyses provide valuable data about variations in vessel forms, classification systems, and the origins of the materials used to construct pots. Because pots, both as objects in themselves and as vessels for other commodities such as grain, oils, wine, and salt, were very often trade objects, technological analyses can reveal information about ancient trade routes and trading patterns. Technological analyses may use neutron activation analysis, X-ray diffraction, or ceramic petrology to identify trace elements in clay or temper to gather information about the production, distribution, use and disposal of ceramic artifacts.
Technological analyses
In one type of technological analysis, the archeologist attempts to understand the physical and mechanical properties of the ceramic material. Experiments may be designed to gather information about thermal shock, tensile strength, and crack propagation in ceramic vessels. In addition, the impact of any surface treatments on a pot’s function may be assessed.
In a second type of technological analysis, the types of clay and tempering materials are analyzed to determine the origins of the materials used in the pot’s construction. Mineral composition may be determined by petrographic analysis or x-ray diffraction. Petrographic analysis employs a microscope and polarized light to identify the mineral used as temper, based on the temper’s optical and morphological characteristics. In x-ray diffraction, the specimen is bombarded with electrons to obtain an x-ray diffraction pattern characteristic of the minerals present in the object. At an elemental level, clays can be analyzed by such techniques as optical emissionspectroscopy, inductively coupled plasma spectroscopy, x-ray fluorescence, neutron activation, proton-induced x-ray
KEY TERMS
Artifact— A man-made object that has been shaped and fashioned for human use.
Atomic absorption spectrometry— Method of analysis in which the specimen is placed in a flame and the light emitted is analyzed.
Ceramic petrology— Study of the origin, occurrence, structure, and history of the material used in a ceramic object.
Crack propagation— Growth of cracks in a material.
Fertile Crescent— Crescent-shaped area extending from Israel to Turkey and Iran, where domestication of plants and animals first occurred.
Firing— Treatment of a ceramic object with heat.
Inductively coupled plasma spectroscopy— An analytical technique in which plasma from the sample, heated by flame to a much higher temperature than ordinary combustion flames, is sampled either by emission spectroscopy or mass spectrometry.
Microprobe analysis— A chemical microanalysis technique based on the analysis of x rays emitted from a very small sample area.
Morphology— Study of structure and form.
Neutron activation analysis— Method of analysis in which a specimen is bombarded with neutrons, and the resultant radio isotopes measured.
Temper— To moisten and mix clay to achieve the proper consistency for use in ceramics.
Tensile strength— The maximum stress from stretching that a material can experience without tearing.
Thermal shock— Effect of rapidly subjecting a material to a very large change in temperature.
Thermoluminescence— Light emission accompanying the heating of a material.
Typology— The study of artifacts based on observable traits such as form, methods of manufacture, and materials. Classification should not be based on an artifact’s function because this can not be unambiguously determined.
X-ray diffraction— A method using the scattering of x rays by matter to study the structure of crystals.
X-ray fluorescence spectrometry— A nondestructive method of analysis in which a specimen is irradiated with x rays and the resultant spectrum is analyzed.
emission, microprobe analysis, and atomic absorption spectroscopy. Each of these methods evaluates the wavelength of energy either emitted or absorbed when the electrons, protons, or neutrons present in the clay of the vessel are disturbed by a source of radiation. These indicate the chemical elements present in the sample.
Typological analysis and other dating techniques
Typological analysis is the systematic classification of material culture into types based on similarities in form, construction, style, content, and/or use. Before the advent of modern dating techniques, typological analysis provided the chief basis for dating material objects. The underlying premise of the technique is that, in a given region, artifacts that resemble each other were created at about the same time, and that differences can be accounted for by gradual changes in the material culture.
Ceramic objects have thus been dated relative to each other based on typological or stylistic shifts in a material culture through time (seriation). One of the earliest seriation techniques used an indexing scheme to measure the similarity between artifacts. Today, computer-based statistical methods, including multidimensional analysis, factor analysis, and cluster analysis, are commonly used to date objects based on stylistic similarities.
In luminescence dating, a ceramic object is heated to produce a thermoluminescence signal characteristic of the length of time the objects have been buried. This technique is based on the principle that objects that have been buried a long time show greater luminescence intensities than those buried a short time.
Resources
BOOKS
Maloney, Norah. The Young Oxford Book of Archeology New York: Oxford University Press, 2000.
Renfrew, C., et al. Archaeology: Theories, Methods, and Practice. 4th ed. New York: Thames and Hudson, 2004.
Sullivan, George. Discover Archeology: An Introduction to the Tools and Techniques of Archeological Fieldwork. Garden City, NY: Doubleday & Company, 1980.
Randall Frost