S-6 Stain Remover
Stock Solution A
Potassium Permanganate - 75 grains - 5.2 g - 90 grains
Water to make - 32 U.S. fl. oz. - 1L - 40 Imp. fl. oz.
Stock Solution B
Cold Water - 16 fl. oz. - 500mL - 20 fl. oz.
Sodium Chloride - 2 1/2 oz. avdp. - 75.0g - 3 oz. avdp.
*Sulfuric Acid, C.P. - 1/2 fl. oz. - 16.0mL - 5/8 fl. oz.
Water to make - 32 U.S. fl. oz. - 1.0L - 40 Imp. fl. oz.
Formula supplied in both U.S. Customary and Metric Units. Imperial Units based on ratio (liquid) of 5 Imperial fluid ounces : 4 U.S. fluid ounces. Imperial weights based on 1 1/5 oz. avdp./Imp. Qt. : 1 oz. avdp./U.S. Qt.
*ALWAYS ADD THE SULFURIC ACID TO THE SOLUTION SLOWLY AND STIR IT CAUTIOUSLY. NEVER ADD THE SOLUTION TO THE ACID, BECAUSE THE SOLUTION MAY BOIL WITH EXPLOSIVE VIOLENCE AND BURN YOUR FACE AND HANDS.
If you discover yellow or brown oxidation stain on a negative, first bleach it in an acid potassium permanganate solution containing sodium chloride (salt). This solution will convert the silver to silver chloride and will change the developer stain to a form that can be washed out. The brown stain of manganese dioxide formed in the reaction is removed by bathing the negative in a sodium bisulfite solution, and the silver chloride is then redeveloped to a silver image. Inasmuch as the stain remover solution will convert the silver sulfite to silver chloride, it can also be used for restoring faded negatives in which the image has been attacked by sulfur compounds.
Use equal parts of A and B. Do not mix the solutions until you are ready to use them because they will not keep long after mixing. All particles of permanganate should be dissolved completely when preparing Solution A, since undissolved particles are pat to produce spots on the negative.
Here's the process for removing developer or oxidation stain. First harden the film for 2 or 3 minutes in formalin hardener Kodak SH-1. Then wash it and bleacah in the Kodak S-6 stain remover solution for 3 or 4 minutes at 68ºF (20ºC). The brown stain of manganese dioxide formed in the bleach bath is best removed by immersing the negative in a 1 percent sodium bisulfite solution. Rinse well and develop in strong light, preferably sunlight, with any nonstaining deveeloper such as Kodak D-72 diluted 1 part developer to 2 parts water. After this has been done, wash the negative thoroughly.
Developers containing a high concentration of sulfite--such as Kodak D-76--should not be used for redevelopment because the sulfite tends to dissolve the bleached image before the developing agents are upon it.