Chartres Cathedral is the French cathedral famous for its 13th-century stained-glass windows dominated by a distinctive cobalt blue.
The cathedral’s glass was produced mainly between about 1200 and 1250, after an earlier church on the site was damaged by fire. Much of the medieval glazing survived the French Revolution and both world wars, making Chartres one of the world’s most important collections of medieval stained glass.
The intense blue is often called Chartres blue, although it is not a single uniform recipe used in every panel. Medieval glaziers created colored glass by adding metallic substances to molten glass, then painted details onto the pieces before firing them. Lead cames joined the individual pieces into larger windows.
Chartres has more than 150 surviving medieval windows, showing biblical scenes, saints, donors, trades, and the Virgin Mary. Visitors sometimes assume every window is blue, but the collection also contains strong reds, yellows, greens, and purples.