These postcards of the mountains, fjords, glaciers and towns of late 19th Century Norway were created by the Detroit Publishing Company using the Photochrom process.

Invented in the 1880s by an employee of a Swiss printing company, Photochrom was a painstaking and time-consuming technique for applying color to black-and-white images.

The process involved coating a tablet of lithographic limestone with a light-sensitive emulsion, then exposing it to sunlight through a photographic negative.

This caused the emulsion to harden in proportion to the tones of the negative, creating a fixed lithographic image on the stone.

For each tint to be used in the final color image, an additional litho stone was prepared. A dozen or more could be required for a single postcard.

The result: lavishly colored images that far outshone traditional hand-coloring, and were truly impressive at a time when real color photography was still in the first stages of development.