Vispach Bridge and the Matterhorn, Valais.
Image: Library of Congress
These pictures of the sublime landscapes and stately towns of Switzerland were created using the Photochrom process, a technique for applying color to monochrome images with nuance and precision.
Invented in Switzerland by an employee of a printing company, Photochrom was a time-consuming and delicate process.
First, a tablet of lithographic limestone would be coated with a light-sensitive emulsion, placed under a photo negative and exposed to sunlight for several hours.
The emulsion would then harden in proportion to the tones of the negative. The softer portions would be removed with a solvent, leaving a fixed lithographic image on the stone. Read more…