Shelf Life of Home Brew Chemistry

Most formulas will have sodium sulfite in them, which is a preservative. In general, they should have about the same shelf life as a packaged product.

I shoot some argon gas wine preserver into the developer bottle, which allegedly is heavier than air so blankets the film service preventing oxidation.

You could change to FX-55 (Geoffrey Crawley) film developer which has two parts, one which lasts indefinitely and the other (0.1g phenidone and 1.3g sodium ascorbate) which is mixed in just prior to use.

30 Aug 2018

Doc W:

I mix my own "home brew" D-76 (usually 2 L) and store it in dark bottles. Only once have I had to dispose of a little chemistry be it was brown, but that was after 6+ months with lots of head space. I have not had any issues with developer loosing potency in 4-5 months. Like you I follow Anchell's formulas from "The Darkroom Cookbook".

Regards,
Darwin

RPC said:

Most formulas will have sodium sulfite in them, which is a preservative. In general, they should have about the same shelf life as a packaged product.

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+1, I hope!

Shelf life will be different for every single product you will ever mix, and it will depend on chemical impurities in your specific batch of raw compounds, and of course on use and storage conditions. If you get a prepackaged product, at least the impurities in the raw chemicals are known to the maker (c.f. photo grade chemicals), so they can give a better estimate for shelf life. They can also add compounds to reduce the effect of these impurities, e.g. add powerful sequestering agents to bind iron/copper impurities. And these shelf life estimates can still go wrong, c.f. reports regarding sudden death of Kodak's XTol.

If you want to get a handle on shelf life of your favorite home brew liquid, you need to gather experience with it. Use it for a few years, watch it deteriorate and how that affects results. See whether deterioration is dependent on ambient temperature, whether addition of DTPA or Dequest 2000/2006/2010 improves shelf life, whether an inert gas blanket helps shelf life, ...

I've mixed my own Print developers for years and the PQ warmtone developer I use has a conger shelf-life than it's current commercial equivalent. I mix to the commercial strength not the published formula substituting Potassium Carbonate and a small amount of Hydroxide for the Sodium Carbonate. Contrary to many books the formulae with Phenidone have better keeping proporties than the revised Dimezone versions, I'm talking part used/filled bottles. So I've print developers with a shelf life of over 2 years.

I mix Pyrocat HD in water and have had it last well over 3 years with no issues again in partially full bottles, I've some 8 years old in Glycol but don't need that kind of longevity.

Chemicals like Sulphite and Metabisulphite need to be reasonably fresh as they are the preservatives, I sore in old Ilford and Agfa plastic developer bottles some must be over 30 years old but still OK. With Pyrocat it's particularly important the Metabisulphite is fresh, Bisulphite is not really suitable as it can be too low grade (only 60% Metabisulphite compared to 99%).

There should be little difference in storage times comparing home made to commercial chemistry, except for my comment about Dimezone.

Ian

Ian Grant said:

There should be little difference in storage times comparing home made to commercial chemistry, except for my comment about Dimezone.

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Powerful sequestering agents for iron/copper can make a big difference for shelf live - and not only for ascorbate developers. For some reason these are particularly hard to come by as amateur. I have no idea why it's so much easier to get PPD, Sodium Sulfide, Pyrogallol and Bichromate than Dequest 2000 or DTPA.

Distilled water can be used to eliminate the need for sequestering agents.

RPC said:

Distilled water can be used to eliminate the need for sequestering agents.

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This has been beaten to death when ascorbate developers were discussed:

1. "distilled water" can still contain trace impurities of iron and copper
2. Even if you use ultrapure water from a semiconductor facility, you will still bring in iron and copper ions as impurities from the chemical compounds you mix your process liquid from.

Well, it seems there are always exceptions to every rule. But there are plenty of popular developers out there that work well with distilled water.

Thanks for all the responses. This is all very useful. I appreciate it.

One other thing to remember about shelf life is that the packaged materials also need to be prepared with consideration of how they perform if they sit on a retailer's shelves for an extended time. So there often are ingredients included to help prevent pre-mixing storage deterioration. That isn't a concern with "Home Brew".