A Review of the Chemistry of Lith (Infectious) Development

Lith development is produced by a combination of two primary mechanisms; the dependence of induction time on exposure and the autocatalytic continuation phase of development by semiquinone. Each mechanism may be modified in its action by other components of the system. The induction time is influenced principally by bromide ion, both that which is initially present and that which is released from adjacent developing grains and adsorbates to the grain SUI face, advantageously by polyethylene oxides, disadvantageously by some dyes. Semiquinone development is affected by the sulphite ion concentration and system components whose reactions lead to more rapid formation of the semiquinone such as hydroxyl ion and gelatin (arginine).

Additionally, bleaching of the latent image in the low exposure region may play some part in producing a sharp toe to the characteristic curve.