Fixer check solution

Description

A drop in the working fixer shows how much dissolved silver it already holds. An answer in seconds, instead of counting rolls from memory.

How it works

The reagent forms an insoluble precipitate with dissolved silver: if a cloudiness appears and does not clear, the silver concentration has passed the safe limit. An exhausted fixer does not merely work slower — it leaves compounds in the emulsion that yellow over the years, and the print dies quietly.

When it matters most

For fibre prints made to last decades. On film the simpler test is a scrap of unexposed film: if it does not clear in half a minute, the fixer is finished.

Questions and answers

Does this replace the film-clip test?

It complements it. The clip shows speed, the indicator shows accumulated silver. For paper the second matters more.