Combined use of ion beam slope cutting and scanning electron microscopy for the investigation of the 3-dimensional micro-structure of alterated mediaeval glass

Abstract

Ion beam slope cutting (IBSC) has been developed as a preparation method for SEM and TEM to avoid the problems which occur using the common mechanical preparation techniques. IBSC has been practised on metals, plastic composites ceramics and alterated mediaeval glass, too. For the investigation of the 3-dimensional microstructure of the glass samples, IBSC has been the only method, which will enable a small cut without destroying the valuable cultural heritage. By SEM investigations of the ion beam cut, the alteration process of mediaeval glass has been observed starting on the surface and spreading into deeper zones of glass. Vertical and lateral cracks are only developing and spreading in the surroundings of crater erosions. The cracks cause splitting of parts near the surface of glass. Inside the cracks, harmful atmospheric gases, like SO₂ and CO₂, are reacting with the main glass components to alterations salts, which will build up a white and black crust on the surface and in zones near the surface.