Composition roller

A composition roller is a tool used in letterpress printing to apply ink to a bed of type in a printing press. It consists of a cylinder made of a substance known as "roller composition" or simply "composition", a mixture of glue and sugar (in the form of molasses or treacle), with various additives such as glycerin depending on the particular recipe. Early recipes also included gypsum plaster and tar, though these were eventually found unnecessary.