This article is a synthesis of art history, execution, deterioration, and restoration of paintings on glass. The available data from the said disciplines are combined, interpreted, and used to deduct the age of the paintings, to explain the causes of their corrosion, and to devise a plan for their restoration, which the authors themselves have carried out. This is illustrated by before and after photographs. The paintings comprise scenes from the Apochrypha, (referring to the life at St. Anne) and shields with heraldry of them. They must have been executed in the 17th century, although earlier authors tend to assign them to 16th century masters. The glass characteristics and lead pattern corroborate this 17th-century origin, evidential aspects which obviously were overlooked by former investigators. The dirt accumulated through the ages on both sides of the stained glass windows was examined and showed the following compositions: outside -- iron salts, plumbo-jarosite (PbFe₆(SO)₄.(OH)₁₂), calcium sulfate, calcium carbonate, soot and organic matter; inside -- calcium sulphate and magnetite. The rust stains on the glass caused by the dirt were removed with a paste containing 35g Attapulgite clay, 5-10g sodium salt of ethylene-diamine-tetra acetic acid, 15g ammonium carbonate, 15g 30% ammonia, four drops surfactant (Arkopal N 100) and 100ml demineralized water. The above mentioned cleaning procedure lasted from 10 minutes to one day. Retouching, when needed, was carried out with grisaille and contour glass paint powder mixed with polyvinylacetate -- a binder which guarantees the reversibility of retouching. The iron elements of the windows were given anti-rust treatment. The stained windows were, with a view to corrosion prevention and protection against breakage, provided with panes of hardened glass and ventilation channels. -- AATA