Darkroom chemistry for black-and-white film

Film chemistry is documented, but the documentation is badly distributed. The authoritative literature is out of print and unsearchable. Manufacturer sheets are primary sources and genuinely good, but they are written per product rather than comparatively, and they change between revisions without announcement. Forums hold decades of real experience sitting next to confident folklore, with nothing to tell the two apart.

So the work here is reconciliation. Published figures are set against each other with the product, formulation and revision each came from, and the explanation is why two sources differ rather than a vote on which one wins. Where a statement concerns handling, dilution, storage or disposal, it cites a current Safety Data Sheet by revision date. Where the published evidence stops, the article says so instead of filling the gap.

Browse every article by section below, or start from the editorial standards that govern what publishes here.

One thing on this site is not an article. The fixer calculator works out dilutions, converts a count of prints into the silver actually sitting in the bath, and reports it against each of the four separate limits Ilford publishes — which are four, not one, and which is exactly where the fact sheet catches people out. Its headline capacity of forty 8×10 prints per litre turns out to be the same number as the commercial-permanence limit printed two pages later, leaving no archival headroom underneath it at all.

Every figure in it is read off a named sheet at a named revision. Where Ilford publishes nothing — silver per roll of film, an archival limit for resin-coated paper — the calculator says so rather than interpolating a plausible number.