Velox and gaslight paper
1893 (Leo Baekeland, Nepera Chemical)
A photographic paper fast enough to print under ordinary gas or electric light, instead of sunlight. Kodak bought it in 1899 and it made home and shop printing easy.
How it began
Albumen prints were made by laying a negative on paper in sunlight for many minutes. Leo Baekeland, a Belgian chemist in New York, made a paper with a silver chloride emulsion that needed only a short exposure to artificial light. It went on sale in 1893 as Velox.
How it works
The paper is exposed briefly under a lamp in contact with the negative, which makes an invisible latent image. A developer then brings out the picture, which is fixed and washed. Because development amplifies the image, much less light is needed.
Why it mattered
Printing no longer depended on the sun and the weather. Kodak bought the rights in 1899, and the paper underpinned its developing and printing service for amateurs.
Limits and what replaced it
It suited contact printing rather than enlarging. Faster bromide papers for the enlarger, and later colour papers, replaced it.
Today
Gone, but silver-gelatin papers descended from it are still used in darkrooms.