In a platinum print, the paper is first coated by hand with a solution of light-sensitive platinum salts and left to dry in a process called sensitizing. The negative is then placed in direct contact with the sensitized paper and exposed via either sun or artificial ultraviolet light. Following exposure, the print is put in the developer and the clearing bath before the final wash. After the image is dried, the printer can repeat the process of coating the paper and exposing the negative multiple times if necessary. Deacidification of the paper is the final step, and the process results in a single-layer print with the image embedded in the paper fibers.
To help withstand multiple coatings, exposures, and dryings, and to prevent warping, Penn affixed the paper to an aluminum support. Penn devised a system of precise registration punches to ensure the paper and negatives would remain perfectly aligned through the multi-step process. By using different negatives of varying contrasts, Penn was able to achieve great depths of tone and contrast in his final prints.
Irving Penn. Mud Glove, New York, 1975. Gift of Irving Penn, 1996.168.