Lithography was invented in 1798 by Aloys Senefelder and was used initially for printing sheet music. By the 1890s, artists including Pierre Bonnard and Henri de Toulouse-Lautrec had adapted it for artistic purposes, using it to create color prints and posters. Lithography can be one of the most direct printmaking mediums, since images are executed on a flat surface—either a polished limestone slab or an aluminum plate—in much the same manner as crayon drawings or watercolors on paper. After chemicals are used to securely bond the image to the stone or plate, it can be inked and printed. The Expressionists—and many other artists—capitalized on the variety of lines and painterly effects that can be achieved in lithography.