The oil print process is a photographic printmaking process that dates to the mid-19th century. 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.
A significant drawback to the oil print process is that it requires the negative to be the same size as the final print because the medium is not sensitive enough to light to make use of an enlarger. A subtype of the oil print process, the bromoil process, was developed in the early 20th century to solve this problem.
The oil print and bromoil processes create soft images reminiscent of paint or pastels but with the distinctive indexicality of a photograph. For this reason, they were popular with the Pictorialists during the first half of the 20th century. The painterly qualities of the prints continue to appeal to artists and have recently led some contemporary art photographers to take up these processes again.