Darkroom Tip: Developer Dies of Oxygen Exposure

Most developers die by oxidation, not use. A half-empty bottle of stock XTOL or D-76 is quietly expiring no matter how few rolls it's seen; many workers trust opened stock for only a few months.

Slow the clock: decant into small full glass bottles, squeeze the air out of accordion bottles, or drop clean glass marbles in to raise the level. Label mix date on everything. When in doubt, snip-test a film leader — it should turn dark in a couple of minutes in working-strength developer.

At the extremes: Rodinal concentrate is famously immortal, while diluted one-shot developers are a use-it-now affair. Log mix dates in Analogly's Chemistry Tracker and the guesswork disappears.