Photo-Flo

Photo-Flo is Kodak's brand name for a non-ionic surfactant (wetting agent) added to the final film rinse. Active ingredient is a polyoxyethylene alkyl ether — chemically similar to Triton X-100 and the generic "wetting agents" sold by alternative suppliers. Working dilution is 1:200 for the final 30-second rinse after the last wash.^[1]

Photographic uses

• Final rinse on sheet and roll film: Reduces the surface tension of rinse water so that water sheets off the film evenly during drying rather than forming droplets. Without a wetting agent, evaporating droplets leave mineral deposits (drying marks) on the emulsion — the most common avoidable cause of spotted negatives.
• Distilled water matters less with Photo-Flo: A wetting-agent rinse largely compensates for moderately-hard tap water; truly hard water may still need distilled water in the final rinse regardless.

Practical notes

• Use sparingly: One to three drops per litre of rinse water is enough. Over-dosing leaves streaks (opposite of the intended effect) and foams the rinse tray, trapping micro-bubbles on the film.
• Don't reuse the final rinse: A fresh batch each session avoids cross-contamination with developer or fixer residues.
• Generic brands are fine: Edwal LFN, Paterson Film Rinse, Ilford Ilfotol all work interchangeably with Photo-Flo.

Related compounds

The active surfactant is closely related to household dish detergents, but household dish detergents typically include fragrances, salts, and dyes that will re-deposit on film. Use a photographic-grade wetting agent.