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Title: The role of organic pollutants in the alteration of historic soda silicate glasses
Author: Robinet, Laurianne
ISNI:       0000 0004 2725 3358
Awarding Body: University of Edinburgh/Universite Paris VI - Pierre et Marie Curie
Current Institution: University of Edinburgh
Date of Award: 2006
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The stability of glass is linked to its composition and the atmosphere controls its alteration. The organic pollutants emitted by wooden showcases play a role in the alteration of historic glasses. This study examines the effects of acetic acid, formic acid and formaldehyde on objects from the National Museums of Scotland and on replica glasses aged artificially, all with a soda silicate composition. Composition was determined by electron microprobe and analytical decomposition of the Raman spectra was used to establish correlations between glass structure and composition. This allowed interpretation of the structural variations between bulk and altered glass. The structure of the glasses altered by pollutants is characteristic of an alteration by selective leaching, with transformation of the silicates linked to alkali into silanols, which subsequently underwent condensation reactions to form a more polymerised structure. The SIMS concentration profiles of glass aged in artificial and real atmospheres were used to follow the alteration evolution as a function of time, humidity and pollutant concentration. The water film formed by the humidity at the surface and its acidity control the alteration by leaching of alkali and hydration of the glass. Formaldehyde does not act on the leaching reaction while acids accelerate and amplify it. In mixed polluted atmosphere, formates compounds always predominate in the film even at low formic acid concentration. The humidity and temperature fluctuations in museums maintain the leaching reaction. Knowledge of the harmful effect of organic acid pollutants in the alteration of soda silicate glasses will help improve their conservation.
Supervisor: Hall, Christopher ; Lacome, Nelly Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: soda silicate glass ; museum ; sodium formate ; Raman spectroscopy