Degas (1834-1917) took up monotype printing in 1874-75, after the amateur etcher Vicomte Ludovic Napoléon Lepic introduced him to the process. Degas discovered that it gave him greater freedom to improvise and be spontaneous than drawing on paper allowed. In his lifetime he was to produce more than 250 subjects and 400 separate impressions in monotype, far exceeding his etchings or lithographs.
For this monotype Degas worked in the 'dark-field' method. He covered the entire surface of the printing plate in ink and then removed it as necessary to create the image. Le Sommeil shows the inventiveness of Degas's method of handling the ink: he scratched and brushed it, wiped it with a rag and manipulated it with his fingers to create the composition, before fixing it by printing it onto paper.
The pattern of the light and shadow and the distortions in the figure turn this into a dramatic image. Degas found monotype ideal for capturing secret and intimate scenes, such as women engaged in their toilet or in brothel scenes. Degas usually printed two impressions of each monotype subject, one strong, the other weak. He would keep untouched the first impressions (this is a first impression), but he would rework the second with pastel or gouache.