Formulary's Reducer 1 For Negatives is a hypo-potassium Ferricyanide negative reducer, which is similar to both Kodak R-4a and Kodak R-4b. The chemicals in the kit are used to make two stock solutions. Depending upon the relative amounts of the two stock solutions that are used to make the working solution, Reducer 1 can act either as a sub-proportional or as a proportional reducer. A sub-proportional reducer removes silver metal from low density areas faster than it does from the high-density areas. This mode of removal improves over-developed negatives. Working solution amounts depend upon the dilution you use.