Stained glass — Middle Ages

The story behind the answer

These windows are made from small pieces of colored (“pot-metal”) glass joined by lead cames, so the color is in the glass itself rather than merely painted on the surface. Sunlight passing through creates vivid, luminous images and patterns, often arranged into narrative panels. Black or brown vitreous paint was sometimes added for outlines and shading, then fired onto the glass.

They flourished in High Gothic cathedrals (12th–13th centuries) when flying buttresses freed walls for vast openings, from lancets to spectacular rose windows. Beyond beauty, they served as a “Bible in color” for largely illiterate congregations, depicting saints, moral lessons, and local guilds. Famous examples include Chartres and Sainte-Chapelle, where cobalt blues and ruby reds—achieved with metal oxides like cobalt, copper, and gold—still glow centuries later.