Photographic reducing solution

Solution A:

• Dissolve 37 g of NaCl and 37 g of CuSO₄ in 850 ml of deionized H₂O.

• Add concentrated NH₄OH until a deep blue precipitate forms and then dissolves. Adjust the volume to 1 liter with H₂O.

Solution B:

• Dissolve 436 g of sodium thiosulfate in 900 ml of deionized H₂O. Adjust the volume to 1 liter with H₂O.

Mix equal volume of Solution A and Solution B; dilute the mixture with 3 volumes of H₂O and use the diluted mixture immediately.