Achaeometrical Research in Hungary II., 1988

BIBLIOGRAPHY - SUMMARIES - ANALYSES

determining the elemental composition of metal objects. Laser energy can only absorbed to a sufficient degree in metals of high reflecting power and high heat conductivity (Cu, Ag, Au) by using a Q-switch controlled laser of adequate power density. Furthermore, by controlling the resonator of a Q-switched laser, one can vary the power density and the number of pulses emitted with a single laser shot. At a low threshold value of the Qswitch, 50-100 pulses are produced, which create a crater about 0.1-0.2 mm in diameter, and similar in depth. On the other hand, at a high threshold value only 1-2 giant pulses of high power density are formed, which do not penetrate deep into the sample. This operating mode serves only for surface layer investigations at a depth of 1-5 micrometers, and at a surface area of about 0.3 mm diameter. Ancient bronze coins can be analyzed by directing laser shots focused at the sample surface on the edge, in general without having to clean the surface. However, silver base alloys yielded reliable chemical composition data only after the eroded surface layer on a part of the edge of the coin had been scraped off. Also fakes or forgeries can be easily detected, since new materials are usually much clearer than the ancient ones. Also the surface layer of plated coins can be identified by using the giant pulse operating mode of the laser. Controlled laser source of suitable conditions resulted in common calibration curves for various types of copper, or coppersilver alloys in a wide range of concentrations. In general, spectra of single shots informed about the alloy type, or the homogeneity of a sample, but spectra integrated from triple shots on various parts of the sample were applicable for quantitative trace analysis of enhanced detection power, as well as higher precision and accuracy. Gegus E.: Analyzing the Aquincum Organ's Alloys: Methods and Results (University of Veszprém). Abstract = The Greco-Roman Hydraulis Workshop, 98

th Annual Meeting of the Archaeological Institute of America, December 30, 1996, New York (1996) Paper in press. In the Introduction, the history of the sensational find of the organ of Aquincum was outlined, referring to the lecture of Dr. M. Kaba at This Workshop, as well as the paper of Dr. E. Szonntagh delivered at the 97th AIA Annual Meeting in San Diego. Early meanings on the construction material's quality could be corrected only during the restoration of the organ, when a systematic sampling on 22 parts was performed. As analysis methods spectroscopic micro-techniques using only 10-20 mg samples could be applied. A total evaporation globule arc process in alternating current arc served for the detection of minor and trace elements. A microchemical variant of our tube-electrode spray method was applied on the sample solutions as a quasi-absolute analysis method, calibrated through standard stock solutions with known concentrations. In the past years, This solution method could be replaced with the wide-spread ICP-OES technique (see papers of Dr. J. Borszéki and Dr. P Halmos). Inhomogenity study of ancient metal objects was performed by a laser-micro-spectral analysis method especially suitable for determining the elemental composition of samples without surface preparation. Final conclusion of investigations: all our analysis Results do confirm the talent of the Roman organ-makers in selecting the most appropriate materials. Hon G.: Adatok az Északnyugat-Dunántúl későbronzkorának bronzmüvességéhez (Angaben über das Bronzehandwerk aus der Spätbronzezeit nordwestlich Jenseits der Donau) = Acta Musei Papensis, Pápai Múzeumi Értesítői (1989) 15-32. 300