We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
DRY PLATES, FILMS AND PAPERS 175
According to this theory, the recovery of a latent image would always be possible, and would only be a matter of time.
The Explosion Theory. — F. F. Renwick, in a recent letter to the British Journal of Photography, has brought forward an " Explosion " theory of the formation of the latent image.
This theory is based upon the observation made by Dr W. Scheffer that a silver bromide grain on exposure to light violently throws off some part of its substance. Should this take place in the case of the photographic plate, the surrounding gelatine would of course be ruptured by the passage of the particles. Renwick makes the suggestion that the silver bromide grains in the emulsion are encompassed by a complete meshwork of gelatine, and in the unexposed plate these can only be attacked by developers either through the very minute channels left, or by diffusion through the substance of the gelatine itself. When the plate is exposed, the meshwork of gelatine is broken up to some extent, larger sized channels being formed, and the developer thus obtains readier access to the grains of silver bromide. The " explosion " theory is useful in enabling one to grasp the meaning of the " ripening " process. According to this theory, a ripened grain would be one which is in the most highly explosive condition : in other words, the crystallisation of which has, during the cooking process, reached the limit of stable equilibrium, so that any energy derived from outside sources is bound to bring about disintegration.
Skerry * considers the action of light on the photographic plate to take place in three stages : (1) a molecular change, with the formation of a product whose development is very rapid but is greatly hindered by oxidizers, which is itself untouched by oxidizers, and is probably
1 Photographic Journal, 47, pp. 170-173, 1907.