Platinum salts have been used in photographic processes since the 1830s and are in some of the earliest photo-related patents. The exceptionally long tonal, scale warm color and archival permanence are ideally suited for producing “expressive prints” and by the turn of the century, Planotype companies were providing coated papers to the general public. However, around the 1920’s platinum had become so expensive that manufactured papers had disappeared entirely and only a few dedicated workers continued to use the process. In the 1970s, the resurgence of many “alternative processes” brought on the revival of platinum printing. Since pure platinum, like gold, is so stable and permanent, the platinum print is the most archival of any image made on paper. The well-made platinum print can last for centuries, as long as the fine paper that carries it. Beyond their permanence, platinum prints also have a unique appearance. They are amazingly luminous, and even appear to be three-dimensional. This results from the enormous tonal scale composing the platinum image. A silver photograph can’t have more than a dozen or so separated gray tones: the values of the negative are compressed when printed on silver paper. The platinum print however, with up to five times more scale, has by far the most expanded tonal range of any image, in any printed medium, in the world. Platinum prints are contact printed. The negative must be the same size as the image you see. After choosing a suitable paper, (a daunting task in and of itself—the beautiful subliminal qualities of the paper will become intrinsic with the image), the photographer must then become something of an organic chemist. Complex solutions are carefully mixed and measured out in tiny amounts, to make the light-sensitive emulsion that will coat the paper. Modern platinum printers usually intermingle platinum with palladium or iridium salts, to produce subtle variations in “warmth” and contrast. The photographer must rely upon experience and instinct to achieve the desired effects. The platinum, palladium and iron salts that are the emulsion, is hand-coated with a brush onto a sheet of paper. The paper is then dried. It is usually used immediately. Throughout the process, the photographer is well advised to keep a detailed, exact record of every step— the paper used, the number of drops of the chemicals, the proportions of the mixtures, the humidity of the environment and the paper, etc.—so that errors are not repeated. Mistakes are expensive and time-consuming! Even when all goes well, it is not uncommon for a platinum photographer to make between five and fifteen attempts, with various combinations, to achieve the first “perfect print” from a new negative. Platinum is so stable, that even in a photosensitive salt, it is reluctant to change. Exposing a platinum print requires hundreds of times more energy than a silver print. Special ultraviolet lights are used, or sunlight itself. The ultraviolet light “reduces” (purifies) the platinum salt to a darker, pure metallic state. The fully exposed paper is then developed in a special chemical bath. Development is instantaneous. A series of mild acid baths follow to remove any remaining traces of iron and other extraneous material from the paper. The final image is formed out of sub-microscopic crystals of pure platinum metals, embedded in the paper fiber.
