The Effect of Environment on Latent Image Formation and Stability

This thesis uses an unsensitized emulsion and two chemically sensitized emulsions to investigate the effect of oxygen and water vapor on latent-image formation and stability. At exposure times that cause little or no low-intensity reciprocity failure, vacuum treatment of an emulsion can result in photographic speeds significantly lower than those found in a humidified environment. This is presumably due to competition between internal desensitization sites and surface electron traps for conduction-band electrons. Storage of a latent image in a humidified air environment will induce a speed loss in some emulsions. The unsensitized emulsion was most sensitive to environmental factors while the sulfurplus-gold-sensitized emulsion was not. This is presumably due to the composition and size of the latent image. Maximum changes in photographic speed over time require the presence of both oxygen and water vapor. Oxygen alone may cause latent-image decay in some emulsions. Water vapor in a nitrogen environment did not affect latent-image stability. Extended development and gold latensification restored some of the speed loss observed with the unsensitized emulsion. The unrecovered speed loss is due to either latent-image centers being completely oxidized, or being too small to respond to chemical latensification.