Premium
Raman study of model glass with medieval compositions: artificial weathering and comparison with ancient samples
Author(s) -
Ferri L.,
Bersani D.,
Colomban Ph.,
Lottici P. P.,
Simon G.,
Vezzalini G.
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4103
Subject(s) - depolymerization , raman spectroscopy , mineralogy , sulfuric acid , volcanic glass , dissolution , chemistry , weathering , leaching (pedology) , potassium , analytical chemistry (journal) , geology , inorganic chemistry , polymer chemistry , volcanic rock , environmental chemistry , optics , soil water , organic chemistry , volcano , physics , geomorphology , seismology , soil science
Potassium‐rich ash‐based glass is typical of medieval glass windows used in the Central Europe since 1000 A. D.. Glasses with medieval‐like composition were prepared with different amounts of K 2 O (15–20–25 K 2 O weight%) using recipes deduced from archaeometric literature. Raman data of these samples were interpreted on the basis of the Q n units model and of the polymerization index I p and confirm a close dependence of glass depolymerization on the potassium content. Generally, K‐based glasses have high alteration sensitivity to pollutants conveyed by liquid or vapour water (rain, humidity and fog). In this work, the glass alteration processes were studied in terms of structural modifications related to the glass K content. Leaching and network dissolution were investigated by attack with boiling concentrated sulfuric acid and by exposure to high temperature and high pressure bidistilled water, respectively. The weight loss and alteration layer thickness were measured. The structural changes in the glass network and the presence of neoformation crystallized products were determined through linear Raman maps on altered glass cross sections. The more the glass network structure is depolymerized, the more the surface chemical attack is facilitated. The results obtained for the model glasses are compared with those for a set of ancient K‐rich glass fragments. Copyright © 2012 John Wiley & Sons, Ltd.