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.

Le nouvel essor industriel du marché des applications mobiles telles que les smartphones ou les tablettes tactiles nécessite de nombreuses recherches afin de concevoir des écrans en verres encore plus résistant. Le procédé d’échange ionique au potassium permet d’améliorer la résistance mécanique des verres grâce à la substitution des ions Na⁺ par des ions K⁺, de plus gros rayon ionique. Elle permet ainsi de bloquer les fissures superficielles du verre et de réduire la casse du matériau. Ce travail est consacré à comprendre le principe de diffusion des ions K⁺ au sein de la structure silicatée de différents verres. Les paramètres, temps, température et composition verrière, influent sur la cinétique de l’échange ionique. Dans les mêmes conditions de trempe, la réduction de la composition à un formateur et à l’ion mobile permet d’améliorer la diffusion et la propagation des ions au sein du matériau. Les conditions de trempe, thermique et temporelle, agissent sur la cinétique de diffusion des ions. Elles réduisent la facilité de déplacement des ions à travers la structure silicaté du matériau avec un changement de comportement au-delà de 8h d’immersion dans les sels fondus. La substitution des Na⁺ par les ions K⁺ et leur différence de taille modifient l’environnement des sites laissés vacants par les ions Na⁺ et modifie la structure silicatée du verre. La spectroscopie IR permet de mettre en évidence les modifications structurales des verres soumis à ce procédé d’échange ionique. Lors de l’introduction des ions K⁺, la structure du verre se dépolymérise et crée des oxygènes non pontants. Ceci permet de montrer que l’échange ionique conduit à l’amélioration du renforcement mécanique des verres. / The new industrial boom of the market for mobile applications such as smartphones or tablets requires much research in order to touch-screens design more resistant. The potassium ion exchange process improves the mechanical strength of glass by Na⁺ ions substitution with K⁺ ions, of larger ionic radius. It thus helps to block surface cracks in glass and reduce breakage of the material. This work is devoted to understand the principle of K⁺ diffusion in the silicate structure of different glasses. The parameters: time, temperature and glass composition affect the kinetic of ion exchange process. In the same quenching conditions, the limitation of the composition just to a former network and a mobile ion can improve the diffusion and the penetration ions inside the material. The quenching conditions, temperature and time, act on the kinetic diffusion. They reduce the mobility of the ions through the structure of the silicate material with a change of behaviour above 8h immersion in molten salts. Substitution of Na⁺ by K⁺ ions having different size affect the environment of the sites left vacant by the Na⁺ ions and modifies the silicate structure of the glass. IR spectroscopy allows highlighting the structural modifications of the glass submitted to this ion exchange process. During the introduction of the K⁺ ions inside the glass, the silicate structure is depolymerized and creates no-bridging oxygens. This allows to demonstrate that the ion exchange lead to the mechanical improvement of the glass.