From the Kodak Photo-Flo web page: (http://www.kodak.com/country/US/en/health/tiDocs/ti0688/ti0688.shtml)(posted 8678 days ago)Scum on the dry film or plate:
If the concentration of the working strength KODAK PHOTO-FLO Solution is too high, it can cause a scum to form on the film or plate surfaces. If this occurs, rewash the film and retreat it in PHOTO-FLO Solution of reduced concentration.
Scumming can also result from old solutions, biological growth, or solutions that have accumulated gelatin, etc. from over-use.
Scum on the base side usually can be removed by wiping carefully with a clean soft cloth, chamois, or cotton ball. Scum on the emulsion side can be harder to detect, and usually requires re-washing to remove.
Storing Solutions
Concentrates of PHOTO-FLO Solution should last indefinitely if the container is tightly capped.
Because of the convenience and high concentration of the liquid concentrates, mixing of working solution just before use is recommended. Also because of the high concentration of PHOTO-FLO Solution, "one-shot" use delivers the highest quality final rinse while remaining economical.
Capacity
The surfactant capacity of a working tank of PHOTO-FLO Solution will depend in part on the amount of film put through it, the quality of the water used in mixing, and the length of time a working solution is kept in service. Generally, it is recommended that the solution be changed when it begins to bead, streak, or leave scum on the surface of films or plates, or once per week, whichever is sooner.
Formation of slime on tank walls, and / or evidence of biological growth in the tank are also indications that the solution should be changed more frequently.