The latter about 'surface treatment' is bogus. The water with Photoflo dissolved in it will permeate the emulsion. There's no such thing as a 'surface treatment' with a watery solution of a gelatin matrix.This is also a problem with the film itself, that this solution will remain in the emulsion and cause future problems. He taught that this should only be a surface treatment.
Jobo specifically recommends not immersing their plastic reels in photoflo:
"Caution: Stabilizer (or Kodak final rinse, or any Photo-Flo type surfactant) should always be used in the following way: Use a dedicated container for the solution. This solution should be stored and used off the processor (at room temperature). Remove the film from the reels before immersing the film in the solution. If reels or tanks are immersed in these solutions, they will eventually cause processing contamination effects. The reels will become difficult to load. Rinsing or cleaning the reels or tanks after processing will not eliminate this problem."
The Photo-flo was changed daily or more often if a busy day...made from Photo-Flo 2100. I checked into Photo-Flo 600, but it uses a more toxic formula, while the 2100 uses the same as the 200.
Your professor is mostly correct, and his/her advice is the same I have been sharing for decades, including ~20 years here on APUG/Photrio.
Although I wouldn't exactly say the reels are "damaged" - more just a pain to clean.
And I'm not sure your professor is totally correct about the residue remaining in the emulsion. What does happen with the residue is that it causes issues with foaming in developer, potentially resulting in problems with uneven development.
And by the way, it is "PhotoFlo", not "Photoflow."
When I was in college 55 years ago, I took a few photography classes for fun. My professor harped on NOT putting Photoflow solution in the roll film developing tank with reels of film. He claimed that it damaged the reels and cans because it leaves a residue that is hard to remove. This is also a problem with the film itself, that this solution will remain in the emulsion and cause future problems. He taught that this should only be a surface treatment. So he taught removing the film from the developing reels and swishing it through the photoflow soution a single time with the photoflow in a bowl in the see-sawing motion that once was using from developing film at home. I've continued this treatment method, which makes me favor bulk loading 35mm rolls 30 exposures long since my arms aren't long enough to handle 36 exposure length rolls.
In recent years, I see on Youtube nobody is doing it this way and nobody talks about this. They just dump some photoflow in their developing tanks with water and film in them, and swish it around for a while. I think my professor was right. The water on the surface is what causes streaking on negatives, not the water that has soaked in to the emulsion being released later through drying. The emulsion dries from the outside surface so it would be unlikely to contribute to spots and streaking. Photoflow solution can't be very good for the long term storage of negatives. I've never had any spots or streaks on my negatives when done our way, so it works for me. I may be OCD, but this bothers me enough to talk about.
Comments and discussions are very welcome on this topic.
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