Daguerreotype

Daguerreotype, a photographic printing process which takes its name from that of its inventor - a Parisian scene-painter, Daguerre. The discovery was publicly announced in 1839, and Daguerre and his partner, Niepce, received life-pensions from the French Government. The process, though not of any present photographic value, is interesting as being the first practical method of fixing the image obtained by the camera, and on account of the impetus hence given to photography. It is carried out in the following manner: - A smooth copper plate is silvered, and the surface thoroughly cleaned and perfectly polished. It is then exposed in a small box to the vapours of - (1) iodine; (2) bromine. by which operations a film of silver bromo-iodide is formed upon the plate. After being again submitted for a shorter time to the action of iodine vapour, it is ready for use in the camera. A few seconds' exposure suffices for the formation of the latent image, which must be afterwards developed by the action of mercury vapour, obtained by heating the metal to about 170° C. When developed, it is fined by immersing in a solution of sodium hyposulphite, and, if desired, can be toned by means of gold chloride. The operations of sensitising and developing should, of course, be performed in yellow or ruby light.