Vibrant colored postcards from the turn of the 20th century
 

Vibrant colored postcards from the turn of the 20th century
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Milk peddlers in Belgium.

Image: Library of Congress

In the 1880s, Hans Jakob Schmid, an employee of Swiss printing company Orell Gessner Füssli, developed a process to produce colorized images from black and white photographic negatives

Dubbed “Photochrom,” the process was complex and closely guarded. It entailed coating a tablet of lithographic limestone with a light-sensitive concoction, placing it under a reversed halftone photo negative and exposing it to sunlight for up to several hours. The coating would harden in proportion to the level of exposure, and the less hardened portions would be ******* with a solvent, forming a fixed lithographic image on the stone Read more...

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