Artifacts, archaeological

Archaeological artifacts are considered to be objects that have been buried for very long periods of time—sometimes many centuries or even millenaries. After such long periods, they are deeply modified, consisting of mostly a mixture of metallic remnants and mineral products, which sometimes hinders their identification (Fig. 5.2). 

During the long burial period, extended redistribution of material has taken place. While metal went outwards, ions like chloride and impurities from the environment diffused inwards, resulting in a mass of corrosion products that occupies a volume approximately double the initial size. As a consequence, part of the artifact remains 

Excavated copper alloys are also susceptible to accelerated corrosion even a long time after exhumation due to the presence of chlorides coming from the soil that have attacked the alloy and formed a layer of cuprous chloride (nantokite) deep inside the corrosion layers, just within reach of the metallic core. Cuprous chloride is the stage of a series of reactions in the presence of oxygen and moisture that make it very unstable. The overall gross reaction may be written as [249]  

Moreover, the formation of copper trihydroxychlorides accelerates the corrosion of the remaining metal, and is accompanied by an important volume expansion, which results in a fragmentation of the object. This process known as bronze disease can be identified by the formation of spots or patches of a light green loose powder on the surface of the object (Fig. 5.5). 

Mechanisms regulating deterioration processes in the burial state are still rather unknown and little research has been done on the consequences of long-term corrosion on the stability of the objects. Nevertheless, some studies have been performed on metal artifacts, seeking to characterize the surface layer as well as establish a relationship between the composition of the corrosion products and the environment where they formed. 

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The constant half-life of a nuclide is used to determine the ages of archaeological artifacts. In isotopic dating, we measure the activity of the radioactive isotopes that they contain. Isotopes used for dating objects include uranium-238, potassium-40, and tritium. However, the most important example is radiocarbon dating, which uses the decay of carbon-14, for which the half-life is 5730 a. 

Archaeological Artifacts. A Lekythos Greek vase (500 years b.c.) was analyzed by backscattering Mbssbauer spectroscopy [365, 366]. This Lekythos vase has three black human figures with small red-painted details painted on a yellow-fired clay... 

The usefulness of this nondestructive technique may go further than pigment characterization, and it is proposed as an additional method for checking the authenticity of ancient archaeological artifacts. 

Andreani, C., V. C. Nunziante, G. Cinque, G. Gorini, A. Granelli, and M. Martini (eds.) (2006), Atomic and nuclear techniques for the diagnostics and the preservation of archaeological artifacts,. Neutron Res. 14(1), Special Issue. 

James, W.D., Dahlin, E.S. and Carlson, D.L. (2005). Chemical compositional studies of archaeological artifacts comparison of LA-ICP-MS to INAA measurements. Journal of Radioanalytical and Nuclear Chemistry 263 697-702. 

Perhaps the simplest archaeological question that can be answered by chemical means is what is this object made from . The chemical identity of many archaeological artifacts may be uncertain for a number of reasons. Simply, it may be too small, corroded, or dirty to be identified by eye. Alternatively, it may be made of a material that cannot be identified visually, or by the use of simple tests. An example might be a metal object made of a silvery-colored metal, such as a coin. It may be pure silver (in practice, a silver alloy containing more than about 95% silver), or it could be a silver-rich alloy that still has a silver appearance (silver coins with up to 30% copper can still look silvery, in which case the precise composition may well... 

In essence, NAA involves converting some atoms of the elements within a sample into artificial radioactive isotopes by irradiation with neutrons. The radioactive isotopes so formed then decay to form stable isotopes at a rate which depends on their half-life. Measurement of the decay allows the identification of the nature and concentration of the original elements in the sample. If analysis is to be quantitative, a series of standard specimens which resemble the composition of the archaeological artifact as closely as possible are required. NAA differs from other spectroscopic methods considered in earlier chapters because it involves reorganization of the nucleus, and subsequent changes between energy levels within the nucleus, rather than between the electronic energy levels. 

Harbottle, G. (1986). 25 years of research in the analysis of archaeological artifacts and works of art. Nuclear Instruments and Methods in Physics Research B 14 10-15. 

Swann, C. P. (1997). Recent applications of nuclear microprobes to the study of art objects and archaeological artifacts. Nuclear Instruments and Methods in Physics Research B 130 289-296. 

Occasionally, determination of properties of the aqueous solution in equilibrium with the solid, such as pH, conductivity, or concentration of ionic species is also of interest—in particular, in the monitoring of cleaning and consolidation of archaeological artifacts. 

A large number of archaeological artifacts are found in burial conditions. Water acting as a solvent, as well as a carrier of ionic species coming from the soil, is responsible for the migration of the latter—the acid/alkaline attack on the object material and further lixiviation of materials and ionic species from the object. Thus, determination of physical and chemical properties of the soil (pH, conductivity, chemical composition, etc.) is of great importance. 

The application of solution phase electrochemistry for studying the work of art samples and archaeological artifacts requires, as previously indicated, sample treatment via extraction or chemical attack. This is an obvious drawback, because these operations, apart from the requirement of relatively high amounts of sample, usually lead to a loss of information since the solid is dissolved and all signals that are specific for the solid compound or material are not available anymore for measurements. 

It is important to note that the application of electrochemical methods to the analysis of samples of art objects and archaeological artifacts allows much more than only simple identification of certain constituents advanced methods of speciation may provide information about constituents that are only slightly differing in then-composition, or for which there are only slight differences in the matrices in which the components are embedded. Further, redox speciation—and in the case of solid samples, phase speciation—can be used to derive information on production processes or corrosion (deterioration) of the components in the time that passed since their formation. The second part of this chapter is devoted to illustrating the capabilities of advanced speciation strategies. 

One important application of electrolytic treatment is the removal of harmful anions, such as chloride and sulphide, from the mineralized archaeological artifacts. The negative polarization of the system repels the negatively charged species out of the cathode. The process is often accompanied by the formation of either gas or soluble species in the electrolyte. This kind of treatment was carried out to increase the rate of extraction of chlorides from iron (see Fig. 6.1) [295], copper [296], and aluminium [297] mineralized objects. 

In the future we should consider the problem of sampling archaeological artifacts in detail. Also, the question of standard analytical methods for various classes of archaeological artifacts should be considered. 

Radiocarbon dating of archaeological artifacts depends on the slow and constant production of radioactive carbon-14 in the upper atmosphere by neutron bombardment of nitrogen atoms. (The neutrons come from the bombardment of other atoms by cosmic rays.)... 

Further details on this method may be obtained from Benjamin et a . (43) or by obtaining product information about the commercial assay from the manufacturer (Humagen, 1500 Avon Street, Charlottesville, VA 22901). We do not know the half-life of albumin in blood stains on the surface of archaeological artifacts. Dried tissues from museum specimens or frozen samples of great age do retain albumin antigenicity (I, 44). 

Forensic studies suggest that monoclonal antibodies specific to albumin may be used to determine the species of origin of blood stains on archaeological artifacts. A monoclonal antibody that reacts specifically with an epitope on human serum albumin has already been produced. 

Chemical analysis of practically every type is used extensively in archaeological chemistry. There are of course important diflFerences between the typical problems which arise in analytical laboratories and those of archaeological chemistry. Ideally in studies of archaeological artifacts the analytical technique should be nondestructive, and if this is not feasible, only a very small sample is to be removed. If a sample is to be removed, a concerted eflFort should be made not to diminish the object s aesthetic appearance. For example, it may be necessary to drill at the bottom of a bronze vase where the damage is not visible. In the case where sample-taking is not allowed, the artifact must be accommo-... 

Table II summarizes the most often used techniques. The methods are grouped according to categories of archaeological artifacts for which they are considered most appropriate. Colorimetry, potentiometric titrations, UV, and visible range spectrophotometry are used whenever possible, primarily because the instruments are usually available and...

Kostikas, A., Gangas, N. H., Analysis of Archaeological Artifacts, Appl. 

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