Archaeochemistry

Central areas of contribution for archaeochemistry include provenance studies, residue analysis, activity area analysis, and reconstruction of production technologies (e. g., glass working, metallurgy, or ceramics). A growing number of techniques for physicochemical analyses are applied to artifact analysis. For example, in X-ray fluorescence, an item is bombarded with X-rays causing the emission of secondary X-rays whose wavelengths can be measured and are characteristic of the elements present in the item. Chemical compounds and trace elements can be identified by their characteristic emissions when electrically excited, as with optical emission spectroscopy, or from the gamma rays produced as radionuclides decay, as occurs in neutron activation analysis. Chromatographic approaches separate a sample into its constituent components and then measure or identify the components. Spectroscopic techniques identify substances from the electromagnetic spectra arising from either emission or absorption of radiant energy. Each technology has benefits, appropriateness, and principles that hold keys to assist us in unravel the past.

Provenance Analysis

The cultural components of power, wealth, labor, regional interactions, and social organization can be inferred from a detailed understanding of the resources and activities involved in an artifact’s construction and deposition. Provenance determination involves the characterization of an object’s composition (mineral or chemical profile) and the natural sources of raw materials used in its manufacture to reconstruct source material procurement activities including production technologies and trade networks.

Material evidence for early trade between Egypt and Canaan is limited even though written evidence is abundant in biblical and Egyptian documents. Natural asphalt or bitumen (a crude oil by-product occurring in seeps) was used to waterproof reed baskets, as an adhesive, in mortar and cement for building, to pave roads, for mummification, and for other uses. The demand for bitumen led to it becoming an important trade item between Egypt and the Dead Sea. Organic geochemical analysis was used to determine that natural asphalts were imported from the Dead Sea to Egypt between 3900 and 2200 BC and may have continued until much later.

Residue Analysis

To characterize a sample of residue, a small amount of a material, milligram or smaller, is subjected to chemical composition determination by mass spectrometry, chromatography, or other suitable sensitive technology. The results produce a chemical profile that can be matched with known references. For example, scientists developed a technique to determine the color of wine from residues in ancient containers. Using mass spectroscopy, they found evidence for tartaric and syringic acids in jars from Tutankha-mun’s tomb indicating that they had contained a wine from red grapes. In another culinary study, chemical residue analysis of pottery indicated that the Maya were consuming Theobroma cacao, or chocolate, as early as 500 BC, more than 1000 years earlier than previously known.

Activity Areas

Human activities can leave chemical evidence in soils and sediments. Remnants in the solum include micro-debitage from kitchen, ritual, or craft activities, bota-nics, pigments, and incense can all leave chemical signatures discernible from the natural soil makeup. In tandem with and in the absence of macro-remains, chemical analysis of soils and floors can provide evidence for improving our understanding of household organization, the dynamics of domestic, ritual, and craft activities, and the locations of such past activities.

Production Technologies

Glass composition varies by differences in the raw materials and recipes used in manufacturing. Primary glass production encompasses the mixing and manipulation of raw materials to manufacture glass, while secondary work included converting imported glass into final objects. Associating the evidence for glass production in Bronze Age Egypt between its primary and secondary components has implications for understanding Mediterranean trade activity from 1500 to 1000 BC. Control over production and consumption was maintained by the high statuses, and a rise in trade and consumption in the Near East, Middle East, and the Mediterranean was commensurate with the rise of elite groups. Written accounts record pharaonic requests for glass importation, but not for glass production within Egypt.

The silica, lime, and soda used for the manufacture of Egyptian glass varies according to procurement location, opening the opportunity for analysis with chemical fingerprinting. Reconstruction of the production technology of the late Bronze Age glass industry from the analysis of glass artifacts and debris indicates that several steps were involved. After plant ash, crushed quartz, and other raw materials were procured, they would be converted to a raw glass at relatively low temperature (900-950 °C). Incompatible salts were removed by washing raw, crushed glass with water, then the pulverized raw glass would be mixed with a colorant (metal oxides), to emulate turquoise or lapis lazuli, and turned into ingots at higher temperatures (1000-1100 °C). Colored glass ingots were transported to distant workshops for the final steps of creating polychrome glass vessels. Different concentrations of potassium in blue-colored glasses are attributable to different plant ashes used during production, further indicating that glassmaking centers specialized in particular coloration.