Main conclusions from Vidrio EU research programme on the determination of conditions to prevent weathering of ancient stained glass windows and recommendations for end-users and practitioners

The project funded by the European commission on the “Determination of conditions to prevent weathering due to condensation, particle deposition and micro-organisms growth on ancient stained glass windows with protective glazing” (VIDRIO), was carried out by an interdisciplinary group composed of physicists, chemists, microbiologists, geologists and end-users. The scientific programme was mainly based on in situ measurements of existing protective glazing systems in three churches representative of gothic architecture chosen in France and Germany. These measurements were completed by natural and artificial weathering of glass samples. The results of each team were widely discussed and cross-linked all during the project in order to succeed to practical and clear conclusions for end-users and practitioners. The aim of this paper is to summarize the main conclusions and scientific advances of the project, and to write practical recommendations for the people in charge of the monuments. Globally the results are positive for the protective glazing systems, in terms of microclimatic conditions, concentration of gases, deposition of particles, microbiological growth and consequently for glass and grisaille conservation. The in-field experiments allowed also to point out certain particular situations that could lead to improvement of the technical equipments.