Claude glass

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. Claude glasses have the effect of abstracting the subject reflected in it from its surroundings, reducing and simplifying the colour and tonal range of scenes and scenery to give them a painterly quality.