Nieinwazyjna metoda identyfikacji pigmentów in situ – badania przenośnym spektroskopem XRF obrazów olejnych Józefa Pankiewicza

Abstract

The elementary composition of selected pigments in 39 oil paintings by Jozef Pankiewicz, dating back to the years 1888 –1938, has been determined with the use of a portable XRF - spectrometer built in the Institute of Fluid-Flow Machinery, Polish Academy of Sciences in Gdańsk. The analysis was preceded by tests on samples of modern paints. To compare with the tests results obtained on the paint layers from paintings also the samples of pure historical paints from Jan Matejko palette from 1888 have been tested as well as paints form tubes preserved in a cassette of anonymous painter, sated back to early 20th century. The detection range of the spectrometer covers the elements of the atomic number 50 > Z > 18. A high-energy source of excitation has been employed (IS601.5, Italstructures) producing a collimated beam of 4 mm diameter and a detector (AXAS, Ketek) of high energetic resolution (FWHM <= 155 eV for the MnKα line) and high sensitivity, which allowed for detecting even trace amounts of elements in paint layer. Basing on the measurements the average volume of the lines of elements present in particular pigments has been established, as well as the factors infl uencing their value. Detection of the elements: Pb, Zn, Cr, Cd, Cu, As, Co, Fe, Hg, Sr, Ba, Sn, Sb, Ti, Ca, Se, Mn in the paint layer of paintings allowed to identify led-, zinc- and titanium-white, ochre, chrome -, strontium-, zinc, Neapolitan and cadmium-yellow, vermilion, cadmium- and iron-red, cerulean- and Prussian blue, cobalt-violet, emerald-, Schweinfurter and vermilion-green, green earth, sienna, umber, iron-, bone and cobalt-black. Apart from the above the composition of primings, extenders added to paints and in cases where it was not based on light elements – the base of organic red. Some pigments turned out to be dating ones (the fi rst use of cobalt-violet – 1908, of cadmium-red – 1919, titanium-white – ca. 1938). The advantages of this method, in relation with the methods of determining the elementary composition of paints used so far are: complete non-invasiveness, testing in situ, high sensibility (of energetic resolution), introducing a quasiquantitative analysis next to the qualitative one, easiness of use and short time of measurements. Besides, this technique allows also for obtaining information on the elementary composition of lower strata, depending on the permeability of upper ones.