ARCHAEOMETRIC INVESTIGATIONS AT THE UNIVERSITY OF SOFIA,BULGARIA

The paper presents a brief overview and history of archaeometric research using instrumental neutron activation analysis at the Faculty of Chemistry of the University of Sofia. The archaeometric projects are listed and some of the results obtained in the investigations of glass, pottery and metals are described.     

THE POSSIBLE FRACTIONATION OF LEAD ISOTOPES IN ANCIENT METALLURGICAL PROCESSES

The possibility of lead isotope fractionation in ancient lead production is examined. Kinetic theory relating to isotopic fractionation in non-equilibrium evaporation is considered and the feasibility of the alteration of lead isotope abundance ratios in ore roasting and smelting is assessed. Previous experimental work is shown to have been inconclusive and conclusions are drawn on the need for further research to quantify the possible extent of fractionation in practice.     

QUANTITATIVE ANALYSIS OF COPPER-TIN BRONZES BY MEANS OF GLOW DISCHARGE OPTICAL EMISSION SPECTROMETRY

Glow discharge optical emission spectrometry (GDOES) has been used for obtaining calibration curves for copper, tin, lead, silver, antimony, arsenic, zinc and iron from standards including copper-base alloys (Cu 61.33-99.95%) and from bronze Punic coins. The GDOES results were calibrated using atomic absorption spectroscopy with inductively coupled plasma atomization (ICPAAS) to analyse the standards and coins. For all these materials, the results show that via GDOES it is possible to obtain reliable and reproducible calibration curves for copper, tin, lead, zinc and iron with a linear behaviour as a function of the content. The quantitative GDOES and ICPAAS data for the coins have been also compared with those obtained via X-ray fluorescence (XRF) and it is shown that GDOES, ICPAAS and XRF agree well with one another considering that the bronze coins are inhomogeneous to some degree. As an example of GDOES analytical features, a depth concentration profile through a thin bronze patina is shown and briefly discussed.     

ANALYTICAL INVESTIGATION OF ARCHAEOLOGICAL POWDERS FROM GÖLTEPE (TURKEY)*

Nine powder samples originating from the archaeometallurgical she in Göltepe, southern central Turkey, have been analysed. Bulk analyses, using X-ray fluorescence and X-ruy photoelectron spectroscopy, and single particle analyses, using electron probe X-ray microanalysis, were carried out. The analyses were focused on determining the inorganic elemental composition of the samples and the distribution of particle types in the nine powder samples. In addition, the powder samples were classified on the basis of their elemental composition using multivariate techniques. The objective of this study was to characterize the powder samples and to establish an association with archaeological data from the site     

LUMINESCENCE DATING OF POTTERY FROM LATER PREHISTORIC BRITAIN*

Dating of later prehistoric settlements relies heavily on potter; typologies in England and yet there has been little scientific dating in order to verify these typologies. In this work, luminescence dating techniques were applied directly to the pottery which forms the typological framework. Excellent agreement was obtained between the luminescence ages, and archaeological age ranges for known‐age pottery sherds with diagnostic form and surface decoration. A lower correlation, however, was found in several regions between the luminescence ages for undecorated body sherds and the archaeological assessment which was necessarily based solely on fabric, suggesting the need for reassessment of these fabric chronologies.     

THE JUDICIOUS SELECTION AND PRESERVATION OF TUFF AND TRAVERTINE BUILDING STONE IN ANCIENT ROME*

The Republican and early Imperial monuments of Rome are, for the most part, built of tuffs quarried from at least seven pyroclastic deposits erupted from nearby Monti Sabatini and Alban Hills volcanoes. Remarks by Vitruvius (2.7.1–5), field observations of the monuments, and petrographic and rock testing studies of samples from Roman quarries demonstrate that Roman builders developed a good knowledge of the diverse material properties of the tuffs over centuries of use and exposure. Measurements of compressive strength, specific gravity, water absorption and adsorption of water vapour confirm that the petrographic characteristics of each tuff lithology strongly influence its strength and durability. Early construction utilized weakly durable, soft or vitric tuffs such as Tufo del Palatino or Tufo Giallo della Via Tiberina that are susceptible to decay, as at Temple C (290 bc ) of the Largo Argentina Sacred Area. Late Republican structures, such as the Temple of Portunus (80–90 bc ), employed somewhat durable, vitric–lithic Tufo Lionato reinforced with travertine, a durable limestone quarried near Tivoli. Roman builders selected the material properties of the tuffs to advantage for specific structural elements within large public monuments of the first century bc and the first century ad , as at the tabernae of the Forum of Caesar (46 bc ), where an upper storey of lightweight Tufo Lionato is supported by robust, lithic–crystal Lapis Gabinus pillars and flat arches reinforced with travertine. The tuffs are not very durable building stones; Romans preserved them with protective stucco, and travertine and marble cladding. Their high water intake, coupled with direct exposure to rain, daily fluctuations in relative humidity and urban weathering at present makes them especially vulnerable to decay.     

The Material Characterization of a Santamarian Ceremonial Axe

The characterization of a ceremonial bronze axe is described. The axe is assigned to the Santamarian culture of north‐west Argentina, c. 1000–1470 ad, and was selected to increase presently limited knowledge of prehistoric metallurgy in the Andean region of Argentina. The characterization methods used were electron probe microanalysis, gamma radiography, X‐ray diffraction, optical metallography and microhardness testing. The axe was well cast in a bivalve mould, with the only defects in the area of an ancient fracture. The analysis showed that it is made from a tin bronze with a, probably, accidental addition of lead. Arsenic was found as a surface contamination, probably deriving from arsenic in the water of the stream in which the axe was found. The axe shows that Santamarian craftsmen had the skill to decorate the axe in an artistic style with a strong local accent while providing a functional, annealed and cold‐worked cutting edge.