![]() Silver halides are white, but slowly turn yellow, then brown, and finally black when exposed to light. Unexposed black-and-white film or paper contains silver salts (silver halides) as the light-sensitive material embedded in a gelatin layer. More recent recommendations are also presented, including adding a toner treatment to the conventional processing sequence. This Note summarizes traditional procedures for processing silver gelatin photographic films and fibrebase papers for maximum permanence. This has been the subject of numerous intensive discussions in the photographic literature over the years. If residual fixing salts are allowed to remain in the photograph, they may seriously jeopardize its permanence. ![]() For example, chemical compounds used in the fixing step during processing may cause black-and-white photographs to discolour. Pollutants such as hydrogen peroxide or hydrogen sulphide may originate from external sources, but other residual chemicals in a photographic film or paper may result from poor processing procedures. Correctly processed black-and-white silver gelatin films and fibre-base prints, while essentially stable to dry heat and visible light, are nevertheless susceptible to image deterioration when exposed to aggressive chemicals. ![]() Therefore, processing must be carried out judiciously. Thus the use of an acetic acid (vinegar) stop is the preferred method.CCI Note 16/6 is part of CCI Notes Series 16 (Care of Photographic Materials) IntroductionĬorrectly processing contemporary black-and-white photographs contributes significantly to their longevity. In addition, acetic acid is one of the constituent ingredients of the fixer solution so stop bath carryover serves to assist the fixers longevity. Additionally, acetic acid is a volatile acid meaning it evaporates away leaving no residue. This strength effectively stops development quickly by neutralizing the alkaline developer without much gas generation. This is ordinary vinegar 1% - 2% strength. This is the preferred method because we can use a very dilute solution of acetic acid. Most of the time the contrast reduction is so minuscule a water bathe is quite satisfactory.ģ. The result is a slight reduction in contrast. This action is not uniform as retained developer quickly exhausts in the high-density regions and continues to work for a time in low-density areas. This is due to fact that the film is sponge like and retains developer. This bathe effectively rids the film of the developer but its action is slow thus some development action continues for a time. ![]() Now the film is in danger of being ruined by the formation of internal gas bubbles and pinholes. In addition, along with the neutralization process, carbon dioxide gas is generated. Thus, we try to avoid direct transfer of the film to the fixer. This is because, if an acid solution directly contacts a alkaline solution, chemically the solutions are neutralized. This works but the life of the fixer solution will be shorted due to the transfer of developer carryover. Remove the film from the developer solution and immerse the film in the fixer solution skipping any intermediate bathe. After development we fix the film (render it permanent) by bathing it in a fixer solution that is highly acid. We develop film in a solution that is highly alkaline.
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