My last modification of the Dignan 2-bath developer in order to get better results, at room temperature, is as follows:
500 ml water
9 g Sodium Sulfite
1 g Potassium Metabisulfite
11 g CD4
Water to make 1 liter
pH should be acid
Time duration: 10 minutes (or more)
Note: Keep bath A in a dark bottle to prevent oxidation and reusage
500 ml water
25 g Potassium Carbonate
0,6g Potassium Bromide
Water to make 1 liter.
pH is aimed to be about 11.
Time duration: 10 minutes or longer with constant (non stop) agitation for less grain.
Bath B may be one shot or reusable. No rinse or wash between bath A and B.
After bath B, a stop bath with 40ml of Vinegar per liter water is good to prevent basic contamination of the bleach bath and fixer.
And now, which bleach bath is suitable? Ferric(III)-Ammonium EDTA based bleach is good and Ammonium Thiosulfate as fixer is also a good option. But there are some more alternatives like Ferricyanide and Copper Sulfate & Salt for the bleach and Sodium Thiosulfate (Hypo) for fixer.
What only few people know is that Povidone-Iodine (sold under the brand Betadine) may also be used as bleach. Using a 10% solution of Povidone-Iodine, it takes about one hour to act. Like other bleach baths, it also needs aeration to work better.
Some examples of photos developed with the modified Dignan 2-bath as above, bleached with Betadine and fixed with Sodium Thiosulfate based fixer. The fixer also needs much more time to act, also one hour.
Conclusion: Betadine (Povidone-Iodine) works very well (IR scanning didn't show any remaining silver) and Sodium Thiosulfate works well too, both need much more time than regular accepted bleach and fix baths.