Determination of the elemental composition of historical glasses using a portable X-ray fluorescence analyzer

Abstract

Historical glasses are complex multicomponent systems that can be modeled by restricting their composition to three or four most important main components and considering the other ones as additives. We present an analysis of glass samples in K₂O – CaO – SiO₂ system, some of them contain sodium along with potassium and small amounts of different additives (oxides of iron, antimony, arsenic, manganese). Study of the aforementioned objects does not provide for their removal outside the museum storage areas, which substantially limits the range of the methods to be used for their analysis. We have demonstrated the possibility of using a portable X-ray fluorescence analyzer in determination of the compositions of historical glasses, including objects of cultural heritage, the study of which can only be carried out by non-destructive methods of analysis. Determination of compositions of silicate glasses that do not contain lead or with a low lead content is considered. The proposed procedure suggests using the programs for fundamental parameters to determine the elemental composition of the glass with subsequent recalculation of the content of elements into oxides, which makes it possible to estimate the oxygen content in the sample. The content of the other light elements that cannot be determined by an XRF-analyzer used (elements with atomic numbers less than 13) is determined as follows. The literature data indicate that the objects under study do not contain lithium, boron, carbon, nitrogen and fluorine. Magnesium was not specially introduced into the composition of historical glasses, but appeared only as an admixture to limestone or potash thus providing only a semi-quantitative estimation of the magnesium content from the known experimental value of the potassium and calcium content and recalculation to oxides. We determined the sodium oxide content in glass by the difference subtracting the content of all oxides from 100%. Although this technique provides only estimation of the sodium content in glass, it is important in answering the question of whether sodium was added to glass specially or entered it as an impurity in potash.