Bauer, a chemist, has analyzed the composition of stained glass windows and that of the corrosion; he has established a relationship between the corrosion and both industrial pollution and climatic conditions. The green and the blue cobalt in the observed samples served as protective layers. Bacher sets out open questions concerning the variable degrees of corrosion on the same stained glass window or on samples of different origins. He describes the techniques in Austria for prolonging the life of the glass: varnish, protective and waterproof coatings, fixing agents.