PLATINUM-PALLADIUM PRINTS
The platinum process, like many of those alternative processes from the late 19th and early 20th centuries, requires a negative the same size as the final image. This is because the platinum sensitiser is only sensitive to ultraviolet light.
The platinum print is made by hand-coating a sheet of paper, by brush, with light sensitive chemicals containing platinum and palladium metal solutions. The ratio of the two metals can be slightly adjusted to control the colour of the image – a higher proportion of platinum will result in a cooler image, while more palladium will give a warmer image.
Once the sensitised paper is dry, the negative is registered on top, placed in a vacuum frame to ensure complete contact and exposed to ultraviolet light. After exposure the negative is removed from the paper and the print placed in the developer where the image appears instantly. The print is rinsed, placed in several successive clearing baths to remove unwanted chemicals and metals and finally washed and dried.
The resulting print will have archival properties far in excess of any other photographic medium, making it desirable to collectors and galleries.