ToF-SIMS analysis for leaching studies of potash–lime–silica glass

In this work the durability to acidic solutions of two kinds of potash–lime–silica glasses with compositions typical for mediaeval stained glass was investigated. The low amount of network formers such as silica and alumina, and the high amount of network modifiers such as potassium and calcium, give to the glass a lower chemical stability compared to modern glass. Studies on its durability are of interest to understand degradation mechanisms. In particular the leaching procedure was focused on determining any correlation between the type of acid and the corrosion of glass independently from the pH value, which was kept constant during the different acidic treatments. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is a valuable tool to study compositional variations of glass, giving useful information concerning provenance, effects of the conservation environment, of weathering or leaching processes and about the compositional differences between the corroded layer and the bulk as a function of depth. In spite of that the insulating properties of glass, the surface roughness and the parameters used for the measurements can lead to possible misinterpretations of the results; in this paper these difficulties are discussed, in order to better interpret the analyses performed on leached glass. ToF-SIMS data are influenced by strong matrix effects making quantification difficult; for this reason the quantitative composition and surface morphology of the leached layer were additionally investigated with scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM–EDX).