Wetting Agent

Overview

Water has surface tension. On a hanging film strip that tension pulls water into beads, and those beads dry at different rates from the rest of the emulsion, leaving hard-edged marks that are almost impossible to remove from a negative.

A wetting agent is a surfactant: it breaks the surface tension so the rinse water sheets off evenly instead of beading. One drop per 200 ml is usually enough. More is not better — an over-strong solution leaves a greasy film that attracts dust and can interfere with printing.

The step takes one minute, is not agitated, and is followed by hanging to dry without rinsing. It is the cheapest insurance in the whole process.

What it does well

• Prevents drying marks and water spots on negatives
• Works in seconds and needs no rinse afterwards
• Also useful in the final rinse for fibre prints before drying
• Very economical — a bottle lasts years
• Pairs well with a distilled-water final rinse

Safety notes

Working notes

• Use a dedicated container. A tray that once held fixer will contaminate the solution.
• Never agitate — foaming is the failure mode and foam leaves marks.
• Hang film with a weighted clip at the bottom so the strip dries straight.
• If you see drying marks anyway, soak the strip again in fresh wetting agent for a minute and re-hang.

Compatible with