Raman Identification of Ancient Stained Glasses and their degree of deterioration

Philippe Colomban (1) , Marie-Pierre Etcheverry (2) , Magali Asquier (1) , Mathieu Bounichou (1) , Aurélie Tournié (1)

1 LADIR - Laboratoire de Dynamique Interactions et Réactivité
2 LRMH - Laboratoire de recherche des monuments historiques

The aim of this investigation was to establish a Raman procedure for on-site identification of stained glass windows and their deterioration level. This study of a representative series of stained glass pieces dating from the 13th-17th, 19th and 21st centuries made it possible to classify the glasses into four types: Type 1 (rare, Ca-rich Na silicate), Type 2 (rare, Na-rich, Ca silicate), Type 3 (more frequent, K-Ca silicate) and a variant of Type 3, referred to as 3bis. Ion exchange of the alkali cations has been made in boiling sulphuric acid and related to structural and compositional changes, which have been analysed with IR and Raman spectroscopy, optical microscopy and EDS. Measurements of the film thickness show a great discrepancy between the ion exchange rates of K-Ca (Type 3: 60 Μm/h) and Na-Ca (Type 2: 15 Μm/h) silicates with that of Type 1 Ca-silicate (0.05 Μm/h). IR and Raman spectra provided proof that the nanostructure of the glass has been modified, chiefly by the downwards (Raman) and upwards (IR) shift of the position of the main Si-O stretching peak and a decrease in the intensity of the Boson peak, as well as the Raman 580 cm-1 Si-O bending peak. The decrease in intensity of the narrow ~950 cm-1 Raman peak, assigned to (earth)alkali nano crystallites in the glassy network, is correlated to K/Na ion loss and glass weathering. Consequently Type 3bis samples are in fact glasses, from which the surface is depleted of K/Na ions. Optical micrographs support the macroscopic compositional and structural heterogeneity of the ancient glasses. This work demonstrates the potential of Raman scattering for in situ measurements of the weathering degree of ancient stained glasses.

Mots clés: glass; silicate; conservation; Raman spectroscopy; IR; weathering; stained-glass window

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Philippe Colomban, Marie-Pierre Etcheverry, Magali Asquier, Mathieu Bounichou, Aurélie Tournié. Raman Identification of Ancient Stained Glasses and their degree of deterioration. Journal of Raman Spectroscopy, 2006, 37, pp.614-626. ⟨hal-00120398⟩