I am curious about the effects of adding sodium sulfite to the Rodinal working solution. I have read vague references in threads refering to the grain/sharpness trade-off; speed increase; and gradation changes, specificaly that the compensation effect is reduced. My questions are: 1: What ratios of sodium sulfite have people tried,liked, and why. 2: The sweet spot as far as regards the grain size/sharpness trade off. 3: What happens to the gradation. Specifically, changes to the curve. 4: The films I use are APX100, Verichrome Pan and HP5+. Any experince with any of these emulsions whould be helpfull.

-- Mark Novack (mnovack@telocity.com), March 30, 2001

Answers

What happens depends on how much sodium sulfite you add to the working solution.

Assuming you're using Rodinal 1:50, that usually gives up to a full stop less speed than the ISO rating when the film's developed to a "normal" CI (not the .65 Agfa's recommendations give).

Adding 12-25g/L sodium sulfite can being the speed back up a bit, by 1/3 to 2/3 stop.

Increasing that to 50g/L can give a slight decrease in graininess, but it's very slight.

I've never observed any difference in curve shape with HP5+ using 12g/L to 50g/L sodium sulfite. The curve shape is pretty much straight, essentially the same as HP5+ in D-76 1:1, Xtol 1:1 etc. Delta 100 and Delta 400 have behaved the same way although I don't recommend Rodinal for them.

The only film I've seen change curve shape with the addition of sodium sulfite to Rodinal is T-Max 100.

Its curve shape in D-76 1:1 and 1:3 is pretty much dead straight, while in Rodinal 1:100 a mild shoulder begins at about Zone X; with the addition of 25g/L sodium sulfite that shoulder goes away and the curve straightens right up.

-- John Hicks (jbh@magicnet.net), March 30, 2001.