what was the claude glass
Painting by Claude Lorrain (1655-1660) shows the gradation of tone that artists hoped to emulate with the help of a Claude glass. Man Holding a Claude Glass by Thomas Gainsborough. A Claude glass (or black mirror) is a small mirror, slightly convex in shape, with its surface tinted a dark colour. Bound up like a pocket-book or in a carrying case, Claude glasses were used by artists, travelers and connoisseurs of landscape and landscape painting.