Glass - Back to the Future!

Barbora Holubova:
Barbora Holubova

article posted 18 March 2016

Barbora Holubová graduated in Chemistry of Materials and Materials Engineering with specialization to Technology of Conservation and Restoration from the University of Chemistry and Technology Prague in 2014 for pursuing directly her PhD at the same place at the Department of Glass and Ceramics. Her main field of study is the problematic of glass corrosion with a special focus on means of glass protection. Her work focuses now on the potential use of hybrid inorganic-organic silica based coatings in the field of conservation-restoration practice and building maintenance together with evaluation of the interaction processes of thin films on glass substrates.

Investigation on protective hybrid silica coatings on historical glass:Recent advances and final steps

Barbora Holubová1,* & Zuzana Zlámalová Cílová1 & Irena Kucerová2 & Aleš Helebrant1
1)Department of Glass and Ceramics;2)Department of Chemical Technology of Monument Conservation, University of Chemistry and Technology, Technická 5, Prague, Czech Republic

In everyday life, especially architectural glass elements remain often unnoticed even though, it is an integral part of many civil and religious buildings. Such an exterior architectural glass suffer not only from lack of interest, but also particularly in the case of historical glass, it is heavily endangered by weathering phenomena. Since the protective glazing does not fulfil the optimal aesthetic and protective requirements, there is an increased interest for protective coating applications benefiting from all the assets of hybrid organosilane materials. These materials are characterized by dual behaviour which comes from their structure consisting of an inorganic part (heteropolysiloxane backbone) capable of strong, covalent siloxane bonding to glass surfaces, and an organic part (containing different organic functionalities) providing progress in overall performance of a final coating. In this study, we pursued our previous project designing hybrid silica coatings prepared via the sol-gel process and consisting in mixing a silica-based inorganic matrix (tetraethyl orthosilicate) with different quantities of functionalized Si-alkoxides. With addition of different substances modifying final flow properties, the material was possible to apply with brush onto the glass samples at low temperatures without any heat treatment. Two glasses in the K2O-CaO-SiO2 system, following similar composition to historical glasses used for production of mosaic glass cubes, were used with two different CaO/K2O ratios. The influence of the glass composition of low chemical resistance is further observed. The samples were analysed before and after model aging tests simulating various weathering parameters. In general, we approved that the newly designed transparent low temperature coating is easily applicable to thin films with common restoration-conservator tools, shows good overall homogeneity, improved adhesion to the glass substrate and no colour or chemical composition shifts. Hence, it appears to satisfy the main requirements for the protection of glass exposed to weathering phenomena. Acknowledgments: The authors would like to thank the financial support from Specific University Research (MSMT No. 20/2015). Also, the authors wish to thank to Preciosa, a.s. for generously preparing the glass samples.