THE X-RAY FLUORESCENCE ANALYSIS OF MEDIEVAL DURABLE BLUE SODA GLASS FROM YORK MINSTER

The chemical composition of durable blue soda glass dated to the twelfth century from York Minster, both from the windows and excavated within this building, has been determined by X-ray fluorescence spectrometry. The analytical data are compared with results from specimens of similar date, colour and composition from Old Sarum and Winchester in England and Chartres Cathedral in France. Multivariate analysis of the compositional data reveals that this unusual blue glass may be classified into three principal groups the possible origins of which are discussed. The specimens in one of them are of particular technological interest since they may have been produced from Roman, or slightly later, glass in a manner referred to by the twelfth century monk Theophilus. It is shown that medieval stained glass of the soda-lime-silicate type, vis-a-vis that containing potash as the predominant alkali, is not as rare as hitherto believed.     

ENERGY DISPERSIVE X-RAY FLUORESCENCE ANALYSIS OF ANCIENT COPPER ALLOYS: EMPIRICAL VALUES FOR PRECISION AND ACCURACY

Energy dispersive X-ray fluorescence (EDXRF) analyses are compared with neutron activation as well as atomic absorption analyses of ancient copper-based alloys in order to examine their accuracy and to estimate realistic values for precision and sensitivity of EDXRF. The results show that it is possible to obtain reliable data of the surface composition of objects non-destructively. Better results for bulk composition are usually obtained with drill samples where the sensitivity of the method is at least competitive with atomic absorption spectroscopy with flame atomization.     

X-RAY FLUORESCENCE ANALYSIS OF MUSEUM OBJECTS: A NEW INSTRUMENT

A new X-ray fluorescent analyser is described which uses a miniature X-ray tube or radioisotope source as alternative means of primary excitation. The advantages of this approach as compared to previous methods, particularly where elements low in the periodic table are concerned, is discussed. The second part of the paper describes an application of the technique. The non-destructive analysis of valuable ceramics, where elements low in the periodic table are important for differentiation purposes, has previously presented a problem. By using the ‘Isoprobe’such measurements are possible. In this instance the separation of early Chinese porcelains into Northern and Southern production groups is shown to be possible. Although samples have been ground from the wares for comparison with optical emission spectrometry, it is shown that analysis of the unglazed portions of the pots themselves gave similar results.     

RIETVELD X-RAY DIFFRACTION AND X-RAY FLUORESCENCE ANALYSIS OF AUSTRALIAN ABORIGINAL OCHRES*

Rietveld phase analysis of X-ray powder diffraction patterns and chemical analysis by X-ray fluorescence spectroscopy have been used to characterize a series of red and yellow ochre samples from Aboriginal ochre deposits in South and Western Australia. The ochres were found to have diverse mineralogy, being mixtures of up to seven minerals, and also to have complex trace element signatures. The mineralogical characteristics and geochemistry of the ochres can be used to identify the source quarries. Using this combination of analytieal techniques it may be possible to trace the source of ochres in burial sites and on objects back to the original quarries.     

X-RAY FLUORESCENCE ANALYSIS OF MODERN AND RECENT CHINESE PORCELAINS

X-ray fluorescence analysis of modern and recent Chinese porcelains shows that the Mn/Co ratio is about 2.5 and above for those made before World War II and less than 0.7 for those made after the war.     

NON-DESTRUCTIVE RADIOISOTOPE X-RAY FLUORESCENCE ANALYSIS OF OLD SILVER COINS

The paper presents the results of a feasibility study of the application of X-ray fluorescence analysis to nondestructive analysis of coins. Radioisotope sources ⁵⁵Fe, ²⁴¹Am, ¹⁰⁹Cd and ²³⁸Pu were used for excitation and a Si/Li detector with a multichannel analyser for the measurement of characteristic X-ray lines. Silver and copper in Polish renaissance coins have been analysed. Analysis using Ag K and Ag L lines allows one to distinguish between blanched and unblanched coins. The accuracy of the silver determination using Ag K X-rays is claimed to be ± 0.5% Ag for homogenous coins and ± 1.0% Ag for blanched but well-preserved uncorroded coins.     

X-RAY FLUORESCENCE ANALYSIS WITH SYNCHROTRON RADIATION ON THE INKS AND PAPERS OF INCUNABULA

Non-destructive X-ray fluorescence analyses induced by white synchrotron radiation (SYXRF) have been performed on a page of the Gutenberg Bible and 21 other different single leaves printed in the years 1470 to 1500. Absolute elemental areal densities for the papers and the inks are reported. The known high Cu and Pb content in Gutenberg's ink is confirmed. The elemental compositions of the other inks, if measurable by XRF at all, are in general very low, governed only by a few additional elements and found to be not distinctive for a known printer. This will render an identification of the printer or printing offices by ink composition analysis in the period after 1470 difficult.     

X-RAY FLUORESCENCE CHARACTERIZATION OF THE CORONA FERREA*

X-ray fluorescence (XRF) analyses of metals, glasses and enamels from the Corona Ferrea, or Iron Crown, of Monza are reported. The method followed to obtain quantitative analysis of metal alloys was based on comparison with standards and it is framed on the more general problem of XRF quantitative analysis of irregularly shaped objects with a portable instrument. Preliminary radiocarbon dating results are also reported.     

CHARACTERIZATION OF PACIFIC NORTHWEST COAST OBSIDIAN BY X-RAY FLUORESCENCE ANALYSIS

Several geological sources of obsidian in the Pacific Northwest have been characterized by means of their trace element concentrations, as measured by X-ray fluorescence analysis. The technique is fast and completely non-destructive, making it well-suited for identifying the sources of obsidian from which artifacts were fabricated.     

ENERGY-DISPERSIVE X-RAY FLUORESCENCE ANALYSIS OF CHINESE PORCELAINS USING Am-241

Americium-241 source was used to investigate elements whose fluorescent X-ray energies are between about 25 and 40 keV. We did not find any correlation between the amount of the elements present and the time of manufacture except for barium, which can therefore be used to detect modern reproductions. This method of detection is both quick and non-destructive.     

QUANTITATIVE RESULTS OF XRF ANALYSIS OF ANCIENT COINS BY MONOCHROMATIC X-RAY EXCITATION

The analysis by XRF applied to old coins is improved by use of monochromatic X-ray excitation of variable energy. In addition the effects of relief and irregular shape are eliminated. A method of absolute quantitative analysis without any reference standard has been set up. Results of the analysis of 52 early Greek and 4 late Roman empire gold coins are reported.     

A LOW DILUTION,WAVELENGTH-DISPERSIVE X-RAY FLUORESCENCE PROCEDURE FOR THE ANALYSIS OF ARCHAEOLOGICAL ROCK ARTEFACTS

A method is described for the analysis of archaeological rock artefacts which provides major and trace element data. Wavelength-dispersive X-ray fluorescence (WDXRF) analysis of 2:1 fusion beads permits the accurate and precise measurement of a wide range of elements. Accuracy and precision are nominally 1-5% for elements having concentrations above 3 times the detection limit. The method requires a much smaller sample size than conventional WDXRF procedures and has been successfully used to characterise early millstones; a number of other applications in archaeology are suggested here.