Cinematographic annual : 1931 (1931)

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38 CINEMATOGRAPHIC ANNUAL The Belitzski reducer which is more stable is recommended in preference to Farmer's reducer. Farmer's reducer, as commonly used by photographers, consists of a 1 0 per cent solution of hypo in which is dissolved enough potassium ferricyanide to cause the reduction to proceed at the desired rate. Alternatively a two-bath process is sometimes used which involves the use of a potassium ferricyanide solution of suitable strength for the first bath and an ordinary fixing bath for the second. The two-bath Farmer's reducer can be kept for long periods of time, but its use is more complicated and control is difficult. When the two-bath formula is used, the time of treatment in the first bath is varied to give increasing degrees of reduction from one end of the fade to the other. All parts of the fade are then given the same time of treatment in the second bath. The three reducers mentioned above leave a faint stain image which is not ordinarily objectionable. When a cutting reducer is required which leaves no stain image, the iodine-cyanide reducer is satisfactory but it has the disadvantage of being very poisonous. It consists of a solution of potassium cyanide to which a small quantity of iodine has been added. Another method of producing a fade-out which is free from stain is to bleach the entire length of negative where the fade-out is to be made and then redevelop the image to varying degrees along the length to produce the densities required in the fade. Either of the two bleach formulas given below is suitable for converting the silver image to one of silver chloride or bromide. Ferricyanide-Bromide Bleach (Formula T-lOa) Potassium ferricyanide 20.0 grams Potassium bromide ---- 5.0 grams Water to 1.0 liter Permanganate Bleach (Formula S-6) . Stock Solution A Potassium permanganate ---- 5.3 grams Water to ...... 1.0 liter Stock Solution B Sodium chloride 75.0 grams Sulfric acid (concentrated) -* 16.0 c. c. Water to 1.0 liter For use, mix equal parts of A and B immediately before using. The mixed bath does not keep long. The silver chloride image can then be redeveloped to the desired degree in a developer such as D-16 diluted to one-fourth strength after which the film is fixed in an ordinary fixing bath to remove the undeveloped silver halide. Before redevelopment is attempted, the bleached image should be exposed to strong daylight but not sunlight. The result of the bleaching and redeveloping operation is equivalent to proportional reduction so that the camera fade is not simulated so closely.