Richard Leach Maddox - Invention of Lightweight Gelatin Dry Plates

Invention of Lightweight Gelatin Dry Plates

In photography, the Collodion process was invented in 1851 by Frederick Scott Archer. This invention required only two to three seconds of light exposure to produce an image, but plates had to be sensitized at the time of exposure, exposed while the emulsion was still wet, and processed immediately after exposure in the camera.

When he noticed that his health was being affected by the 'wet' collodion's ether vapor, Maddox began looking for a substitute. He suggested in the 8 September 1871 British Journal of Photography article An Experiment with Gelatino-Bromide that sensitizing chemicals cadmium bromide and silver nitrate should be coated on a glass plate in gelatin, a transparent substance used for making candies. Eventually Charles Bennett made the first gelatin dry plates for sale; before long the emulsion could be coated on celluloid roll film.

Dry plates had been tried before: silver nitrate with a binder of albumen - derived from egg white, and widely used in printing-out paper in the nineteenth century - had been coated on glass; but these proved to be too insensitive for camera use. Gelatin had also been suggested by photo-theorist and color pioneer Thomas Sutton, and the substance would also have been known to Maddox - himself an eminent microscope practitioner - through its use as a holding/preserving base used in microscope slides.

Initially Maddox tried other bases. He combined silver bromide with "vegetable gummy matters" (lichen, linseed, quince), and "starchy substances" (rice, tapioca, sago). "Often I fancied I was just within the doorway when the door closed, and other plans had to be tried." Finally he tried gelatin from a packet of Nelson's Gelatine Granuals.

Maddox prepared a number of plates, exposing by contact-printing them from other negatives, and putting each through a different exposure trial. "The resulting prints were very delicate in detail, of a colour varying between a bistre and olive tint, and after washing dried to a brilliant surface". He later described trials on "out-of-door subjects", but it was "impossible to get some laurels depicted in anything more than black and white" (i.e. without gray-scale tones).

The advantages of the dry plate were obvious: photographers could use commercial dry plates off the shelf instead of having to prepare their own emulsions in a mobile darkroom. Negatives did not have to be developed immediately. Also, for the first time, cameras could be made small enough to be hand-held, or even concealed: further research created 'fast' exposure times, which led to 'snapshot' photography (and the 'Kodak' camera with roll film), ultimately paving the way for cinematography.