Plasters are intended for the external application of materials of such consistency as to adhere to the skin.  The base material composed of gums and waxes and excipients such as burgundy pitch were mixed with the desired medication.  The mass was spread upon a cloth or leather that had been cut for and applied to the desired area.  Plasters were prepared by pharmacists during the 19th and early 20th centuries, but by the 1930’s were commercially prepared.