Medieval stained glass windows were made by adding copper to the molten glass, which created ruby red, deep blue, bright green, golden yellow, and royal purple. Variations in the thickness of the blown glass made subtle variations in the hues.
Medieval stained glass windows were made by adding copper to the molten glass, which created ruby red, deep blue, bright green, golden yellow, and royal purple. Variations in the thickness of the blown glass made subtle variations in the hues.