Rodinal gone bad?

I just got some very disappointing results using rodinal on pan f plus. The film was barely developed at all - both frame numbers and image highlights are just barely visible. I bought two new bottles of agfa rodinal back in January of this year, and my first rolls with them came out fine (they were acros). Then I didn't use the stuff for a half year, and I just souped these rolls today which did not turn out. I used dev times from the massive dev chart: 11 minutes at 20 C with 1:50 solution. It seems my rodinal has gone bad even though I tightly capped the container and even purged with CO2. Does anyone have any idea why this might have happened? One of the main reasons I decided to go for rodinal was its purported long shelf life (and the fact that it is a liquid concentrate).

I think maybe your purging with CO2 killed your Rodinal. Carbonic acid was formed(CO2 and water) and lowered the pH of your Rodinal. I'm no chemist, but I think that is your problem, Rodinal simply doesn't go bad. I've used decades-old stuff and it's still fine.

Nest time, just the Rodinal in the bottle as-is. It will be fine with air space in the bottle. If you need to do something about it, fill up the empty space with glass marbles or squeeze the air out of the plastic bottle.

That seems like a pretty likely theory. Everything I've read about rodinal suggests it lasts forever, so I figured something I did must have prematurely killed it. I have another bottle of it. Thanks for your help.

Time to take some more photos... to replace the ones I lost.

I've had an bottle of rodinal sit, half full for about 6 months and just did some film with no problem.

this stuff will last forever, unless you mess with it

I've had a bottle half full and unused for years (3 I think) in rather poor storage conditions, had no problems at all when I tried a test role this spring.

Peter

sohara said:

That seems like a pretty likely theory. Everything I've read about rodinal suggests it lasts forever, so I figured something I did must have prematurely killed it. I have another bottle of it. Thanks for your help.

Time to take some more photos... to replace the ones I lost.

Click to expand...

Luckily you can replace them!

Try the bad bottle of rodinal as a print dev. Try the 1+25 dilution. Rodinal does make an ok paper dev, but I don't know about your ruined bottle. However, you have little to lose.

If in fact it was the CO2 changing pH that did it, you could measure the pH and compare it with that of the new bottle. If you don't have a pH meter, you can get pH test strips. They are handy to have around. If the pH is really much lower, you can try adding sodium or potassium hydroxide to see if that brings it back to life. I think a lowering of pH would cause a precipitation of p-aminophenol.

More thoughts: the solubility of p-aminophenol in water is rather low. In the usual procedure for making Rodinal, the aminophenol is converted to the soluble sodium or potassium aminophenolate. Given enough CO2, especially under pressure, the sodium or potassium part of the aminophenolate forms the carbonate and the aminophenol base (I think). I don't see any other place for it to go. Your concentrate would probably be a developer of about the strength of 1+50 Rodinal, but if the sulfite were also to react with the H2CO3, you wouldn't even get any activity out of the concentrate. If you want to use a gas, use Nitrogen, and not the oxide. Marbles would be better. Those plastic squeeze bottles are not worth two hoots up a hollow.

Carbonic acid is highly unlikely, given the amount of MaOH in the cncentrate rodinal
magic Gainer's theory seems more plausible
Would adding some carrbonate or some NaOH help in returning the pH and activity back to normal?

There are in the concentrate, of course, lots of Na or K ions, but most of them are balanced by p-aminophenol ions. You may remember that the home brewer of Rodinal is told to stop adding the hydroxide before all of the p-aminophenol base is in solution. There are Na or K ions associated with the sulfite, which becomes sulfate with aerial oxidation, but may also become H2SO3 and Na2CO3 with CO2 reaction. Adding NaOH could help, depending on how far the CO2 reaction has gone. I'm only postulating here. In any case, I'm sure our resident chemists would agree that CO2 is bad for Rodinal, especially since it is usually under pressure when applied. One could calculate the weight of CO2 needed to make the concentrate go bad, but I'm not sure how we would calculate how big a dose it actually received, other than by experiment. It's like the old days when it was widely believed that onion juice could destroy the power of a loadstone. Loadstones were hard enough to come by that nobody wanted to test the belief by experiment for fear that it was really true. Why risk a bunch of Rodinal to see if CO2 could really destroy it when we know for sure it won't help it?