When you scratch a line in an etching plate, it produces a small raised edge called a ‘burr’. The burr, which gives drypoint lines such a sumptuous velvety look, wears away quickly. As a result, the decorative effect of the technique diminishes and the representation becomes
increasingly lighter. Here Rembrandt solved that problem by making areas of shadow darker again with extra lines, for example under the dog in the foreground.