reducer
Kodak R-4a Farmer's reducer
Handle chemistry safely
Wear gloves and eye protection, work with good ventilation, and read the supplier’s safety data sheet before use. Hazard information here is a summary, not a replacement for it. Dispose of all photographic chemistry correctly, in line with local laws and your local authority’s guidance. Never mix waste solutions, and check the supplier’s safety data sheet before disposing of anything.
Ingredients
| Potassium ferricyanide | 37.5 g |
| Sodium thiosulfate pentahydrate | 480 g |
| Water to make | Stock A 500 mL; Stock B 2.0 L |
Notes
Single-solution cutting (subtractive) reducer, mixed from two stocks only at the moment of use. The working bath is 30 mL A and 120 mL B made up to 1 L; half the A gives slower action. The mixed solution goes off quickly. Watch the reduction closely, then wash. Use it on thoroughly washed negatives.
Source
Processing Chemicals and Formulas for Black-and-White Photography (Kodak Publication J-1), 7th edition, Eastman Kodak Company (1977), p. 45
Amounts as published. Chemical forms (anhydrous, monohydrate and so on) change the weights, so match the form listed.