Glass deterioration mechanisms using Total-IBA of Rosslyn glass

(1) Department of Civil and Environmental Engineering, University of Strathclyde, Scotland
(2) University of Surrey Ion Beam Centre, Guildford, England
(3) Scottish Glass Studios, Glasgow, Scotland

Using Surrey’s in-air scanning focussed microbeam with a large-range motorised sample manipulator and a high count-rate spectrometry system for both particle and X ray detectors,  we have analysed deteriorated stained glass from the Rosslyn chapel (built in 1446).  The glass panels were manufactured around 1875 with a “grisaille” technique:  the image is defined by Pb-rich monochrome paints fired into the glass.   Many panels have suffered extreme image loss due to an aggressive internal environment,  and this work aims to uncover the lost imagery by revealing the original artists’ paint strokes.  Using Total-IBA (self-consistent ion beam analysis) methods we have demonstrated that the lost grisaille leaves an (invisible) surface enrichment of grisaille components,  and that the lost image can efficiently be recovered by PIXE (particle-induced X-ray emission) with high acuity, providing invaluable guidance for the restorers and conservators.

From the large data cubes collected (512×512 pixels, front and back surfaces) we will extract PIXE/EBS spectra of selected areas,  infer the composition modifications as a function of depth from the surface,  and interpret these profiles by modelling the grisaille technique used and the expected glass deterioration mechanisms informed by our knowledge of the environmental history of the panel.

Currently there are only a few studies with reliable elemental depth profiles,  using spot analyses (not mapping).

This project is partially funded by The Rosslyn Chapel Trust (Registered Charity number SC024324) Lord and Lady Rosslyn, Owners and Trustees,  and WREN Heritage Fund (www.wren.org.uk)