Created by photographic printmaking process that dates back to the mid 19th century. This technique was often used by Frantisek Drtikol, famous Czech photographer.
Oil prints are made on paper on which a thick gelatin layer has been sensitized to light using dichromate salts. After the paper is exposed to light through a negative, the gelatin emulsion is treated in such a way that highly exposed areas take up an oil-based paint, forming the photographic image.