Sizes, and filling full

The rule of thumb

Choose a container you will empty in one or two sessions, and fill it to the neck. A bottle that lasts six months is a bottle that spends six months oxidizing whatever is left in it.

Which means buying more bottles, not bigger ones

The opposite of the usual advice. Several 250 mL bottles of stock developer, each filled full and opened once, outlast one liter bottle opened six times.

The shelf supports it

132 containers at or under 500 mL out of 191. That is not a coincidence of this archetype so much as a feature of the catalog, and it happens to suit this use well.

Working solutions are a different question

A diluted working solution is usually mixed for a session and discarded or returned, so its container is about convenience and pouring rather than about keeping. A spouted closure earns its keep there, and there are 27 of them.

Fixer can go larger

It is not oxidation-limited, so a liter or a gallon of fixer in a part-full bottle is acceptable in a way the same bottle of developer is not. Standardizing one size across both chemistries wastes one of them.

And the waste container is sized by collection

Not by the process. Whoever collects spent fixer will usually specify what they will accept it in, and that is the constraint rather than how much you generate in a week.

Date every decant

Because the failure mode is time plus air and nothing visible distinguishes a fresh bottle from a tired one. A date in marker is the cheapest control in this property.

Two chemistries, two strategies, one shelf

Developer wants small and full, fixer tolerates large and part-full, and the waste container is sized by whoever collects it. Standardizing one size across all three is how one of them gets wasted.

References