The Library of Congress provides a digitized archive of almost 6,000 Photochrome prints. I’ve browsed through hundreds of these types of images over the years and always assumed they were either hand-colored or early examples of color photography. Turns out, they’re neither. They were colorized from black and white negatives using a type of Lithographic printing known as Photochrome (also Photochrom).
In traditional Lithography, an artist created an image on a plate of smooth limestone through a process of chemical etching. He applied ink, which adhered to the part that wasn’t etched, then pressed the stone against a blank sheet of paper to reproduce the image.
In the 1880s, Swiss chemist Hans Jakob Schmid invented a process that transferred the image from a black and white photographic negative onto a series of up to 15 limestone plates. Using chemicals and various development techniques, Schmid insured each limestone plate carried a different color of the desired image. He then produced a finished print by using all the plates in the standard lithographic process.
Photochrome reached peak popularity over the next few decades, with Europeans and Americans especially fond of mailing postcards with scenes of cities and landscapes. At one penny in the United States, a postcard’s postage was half that of a regular letter’s. By the 1920s, cheaper printing methods reduced photochrome’s popularity, which receded into niche territory as true color photography gained ground in the 1930s.
Besides the archive at the Library of Congress, an even larger selection of some 10,000 digitized photochrome prints is available through the Central Library of Zurich. Wiki Commons provides access to the collection, as well.
“An Introduction to Photochromes” from photographers-resource.co.uk.
“Photochromes: Explaining how they were produced” from photographers-resource.co.uk.
“Color photography” article in Wikipedia.
“Lithography” article in Wikipedia.
“Photochrom” article in Wikipedia.
“Sami People.” Wikipedia.
“Tints and Shades” article in Wikipedia.