Developing ultra low ISO films for direct duplicating

[Raghu Kuvempunagar]

0.5g of ferric nitrate speeds things up noticeably; two more spoonfuls makes it even faster. Cerium ions don’t show much color, so I just rinsed briefly with sodium bisulfite. If you use a lot of iron(III) ions, EDTA may be needed to prevent iron(II) ionsresidue and subsequent discoloration.
If the speed is too slow after using, it might be due to not enough sulfuric acid—some free acid is needed to solve silver. Glafkides’ original formula may not have enough sulfuric acid, which limits capacity (and he got the valence wrong in his book). A little cysteine might also help, but I haven’t compared yet.

Thank you. How long does your bleach remain active and useful after adding Ferric Nitrate? And do you replenish the bleach with Sulphuric Acid and/or Ferric Nitrate everytime it is reused?

 

[Yezishu]

Thank you. How long does your bleach remain active and useful after adding Ferric Nitrate? And do you replenish the bleach with Sulphuric Acid and/or Ferric Nitrate everytime it is reused?

It should remain stable for a long time—ceric sulfate, ferric nitrate, and sulfuric acid are not likely to deteriorate. If the bleaching speed decreases significantly or a large amount of precipitate forms, collect the clear solution part and replenish with some ceric sulfate solution in sulfuric acid.