When the photographic emulsions were applied pressure before exposure, the surface and the shallow internal images were desensitized, but the deep internal image was sensitized.
When undigested photographic films containing the small quantity of sodium thiosulphate or ammonium aurous thiocyanate was incubated after the application of pressure, the surface image of pressed part of films was preferentially sensitized by following exposure.
However, the chemically sensitized emulsions digested to its maximum sensitivity was desensitized under the same conditions.
Also, the total latent image of non-sensitized emulsions incubated after the application of pressure was desensitized by following exposure.
It was shown that the sensitizing product was also formed at the crystal imperfections produced by pressure.
This result supported the Mitchell's theory that the sensitizing product was formed at the surface of the strained and imperfect regions of microcrystals.
The addition of thallous ions has been reported to decrease the desensitization produced by pressure.
This is explained by that silver halide grains containing thallous bromide are subjected to very slight deformation, because of its high hardness number.
View full abstract