Abstract: “This paper deals with an experimental investigation of the future environmental load on the medieval mosaic of the Last Judgement located at the entrance to St. Vitus cathedral in the Prague castle. The mosaic suffers from seasonal changes of the weather pattern including rains and their acidity, the deposition of dust and soot particles from polluted air as well as freeze-thaw cycles. These phenomena influence the conservation state of the mosaic. The tesserae composing the mosaic are mostly made from glass prone to weathering. In order to establish a procedure for an appropriate maintenance, the relation between various weather scenarios and their effect on the mosaic was investigated. At the same time a local method for evaluating a suitable protective coating was developed. Both methods will contribute to better care for the mosaic and also to improve visitors’ aesthetical experience.”

Keywords: medieval mosaic, weathering, degradation, monitoring, protection, climatic tunnel