Fixer

Overview

After development the film or paper is still full of silver halide that was never exposed. Fixer dissolves it — converting the insoluble halide into soluble complexes that the wash can carry away. Until that happens the image is still light-sensitive and still developing.

Rapid fixers based on ammonium thiosulfate work in three to five minutes; the older sodium thiosulfate "hypo" takes ten to fifteen. The trade-off is capacity and odour: rapid fixers are more expensive, work faster, and smell far less.

The critical discipline is knowing when fixer is spent. Silver accumulates in the solution and fixation slows. A two-bath fix — half the time in bath one, half in bath two — is the standard archival practice, because the second bath stays nearly fresh and finishes the job properly.

What it does well

• Makes the image permanent and viewable in daylight
• Rapid fixers cut film fixing to three to five minutes
• Two-bath fixing is the archival standard for fibre prints
• Clears film leaders — a simple way to test strength
• Reusable until capacity is reached

Safety notes

Working notes

• Test strength by dropping in a scrap of unprocessed film leader: it should clear in 30 seconds.
• Fix at the same temperature as the developer to avoid reticulation.
• For archival work, use two baths and keep bath two for the finish.
• Never use the same container for fixer and developer — trace contamination fogs prints.

Compatible with