Until then, virtually all photographs had been in black and white. In the early 1970s, sales of colour outstripped black and white and today it accounts for all but a tiny percentage of the 96 million films sold in Britain each year. There have been refinements since, but the principle of using layers of cyan, magenta and yellow dye to produce a colour image has remained the same. I don't want it to sound like a Doomsday scenario, but ultimately they will break down into a colourless compound. Whites in a print may also turn yellow with time.
Skin tones can turn a deathly blue.
The conditions in which the print is kept determine which dyes go first. Light, heat and humidity are the death of a colour photograph. Many of the most recent works in the Victoria and Albert Museum's vast collection are unlikely to outlast original prints made by the great Victorian photographers, such as Julia Margaret Cameron and David Octavius Hill. The artist David Hockney keeps his work in a cold store in Los Angeles. He acknowledges that much of it has a limited life span.