How long does the stock solution of D-76 last?

[PollitowuzHere]

Going to be mixing a gallon of D-76 soon and wondering how long does the stock last. I'm going to be splitting the solution into two 2L Coke bottles. I develop about 2-3 rolls of 35mm a month, probably going to start shooting more in the coming months. Film used will be a mix of Neopan 400, Tri-X and Plus-X. Thanks!

 

[Bob Michaels]

The answer is in the Kodak D-76 data sheet available here. These data sheets contain answers to many other questions as well.

 

[PollitowuzHere]

Thanks a bunch!

 

[Roger Hicks]

Endless variables. Boil the water and let it cool (expels dissolved air) and store in half litre bottles: many months. Use well-aerated water out of the tap and store in big bottles: as soon as there's an air-space, it will last only a few weeks.

I vaguely recall that the oxidation is autocatalytic: in other words, a vicious spiral, where the oxidation products accelerate oxidation. But I can't remember. Marty (Freakscene) will know far better than I.

Cheers,

R.

 

[Freakscene]

Endless variables. Boil the water and let it cool (expels dissolved air) and store in half litre bottles: many months. Use well-aerated water out of the tap and store in big bottles: as soon as there's an air-space, it will last only a few weeks.

I vaguely recall that the oxidation is autocatalytic: in other words, a vicious spiral, where the oxidation products accelerate oxidation. But I can't remember. Marty (Freakscene) will know far better than I.

Roger is right about autocatalysis - it is best to prevent oxidation from _starting_ rather than thinking that you can arrest it once it has begun.

Water is infinitely variable - I am not sure how much boiling your mix water will help, because although it drives oxygen off temporarily, it does nothing to the ions dissolves in it that are most likely to start the oxidative reactions, and even a tiny air pocket will allow the water to re-equilibrate to ~2 mg/L dissolved oxygen pretty quickly.

I'd say for optimum storage, mix your D76 with deionised water, keep it in full, well-sealed bottles in the dark, or by replacing the air with a non-reactive gas (wine preserver works well) if you need to have a space, and keep careful notes on how it stays active in storage under your conditions. Keep careful track of your results.

I tend to mix a batch and use it within days, so I am not very helpful except in theory, unfortunately.

Marty

 

[Bob Michaels]

...................... I develop about 2-3 rolls of 35mm a month, probably going to start shooting more in the coming months. ...............................

You may want to consider using HC-110 in the future. You can mix it 1:32 or 1:64 (unofficial dilution H) for the original syrup in the bottle as you need to use it. The syrup lasts for years and years.

I have used HC-110 for 12+ years this way. I have always been happy with the final print quality.

 

[tj01]

Stock solution in full tightly closed bottle = 6 months
Half filled = 2 months.
Pg 7 of the factsheet.