KSbOSiO$_4$ microcrystallites as a source of corrosion of blue-green lead-potassium glass beads of the 19th century

TL;DR

This study investigates the role of KSbSiO$_5$ microcrystallites in the corrosion process of 19th-century blue-green glass beads, revealing their presence and potential impact on bead deterioration.

Contribution

It identifies KSbSiO$_5$ microcrystallites as a key factor in the corrosion of blue-green glass beads, providing new insights into the mechanisms of glass deterioration.

Findings

KSbSiO$_5$ microcrystallites are present in deteriorated beads.

These crystallites are absent in less corroded bead types.

KSbSiO$_5$ clusters may cause internal corrosion of the glass.

Abstract

Presently, deterioration of glass beads is a significant problem in conservation and restoration of beaded exhibits in museums. Glass corrosion affects nearly all kinds of beads but cloudy blue-green ones are more than others subjected to disastrous destruction. However, physical and chemical mechanisms of this phenomenon have not been understood thus far. This article presents results of a study of elemental and phase composition of glass of the blue-green beads of the 19th century obtained from exhibits kept in Russian museums. Using scanning electron microscopy, X-ray microanalysis and X-ray powder analysis we have detected and investigated Sb-rich microinclusions in the glass matrix of these beads and found them to be micro crystallites of KSbSiO$_5$. These crystallites were not detected in other kinds of beads which are much less subjected to corrosion than the blue-green ones and deteriorate in a different way. We belive that individual precipitates of KSbSiO$_5$ and especially their clusters play a major role in the blue-green bead deterioration giving rise to slow internal corrosion of the bead glass.