Residue from emulsion cleaner?

Dusty Negative · Jul 10, 2023

I periodically use PEC emulsion cleaner to remove dark specks on my negatives. I use the tip of a Q-tip to apply.

Almost inevitably, some kind of residue remains on the surface. This does not seem to adversely impact enlarging, but it's long made me wonder...

Is this from the emulsion cleaner, or does it perhaps indicate my negs are not completely chemistry-free, and the residual chemistry (whatever that might be....photoflo??) is what I'm seeing. Ergo, I don't just have Dusty Negs, but Dirty Negs, too?

Anyone have thoughts?

MattKing · Jul 13, 2023

I would reach out to Kino, or ic-racer, who IIRC are among those here who work with cine film.

koraks · Jul 14, 2023

Dusty Negative said:
I periodically use PEC emulsion cleaner to remove dark specks on my negatives.

What kind of specs? Btw, avoiding dust & dirt usually works a lot better than trying to remove it. As soon as something has attached itself to the emulsion, it's always a challenge to remove it without leaving some kind of traces.

I'm not surprised your cleaner leaves some residue. Even 96% ethanol is still 4% water and some other stuff, a tiny part of which will be solids that won't evaporate. Moreover, whatever you smear on the film will dissolve or carry muck that happens to be on the film and deposit it somewhere else as the cleaner evaporates. You're probably seeing a combination of these factors. If it doesn't create problems with scanning or enlarging, I wouldn't worry about it too much.

For what it's worth, when I have a case of dirty negatives, I usually rewash them, optionally using mechanical removal (i.e. gentle brushing with a soft brush) if the dirt is really persistent. Especially the latter carries the risk of additional damage. Sometimes that risk is offset by the possibility of recovering negatives that are otherwise unusable. Again, prevention is a better cure.

guangong · Jul 14, 2023

Qtips can also leave fibers and lint behind. I have only rarely used film cleaner on slides that have suffered extreme damage. Otherwise, easier and safer to simply rewash film. For movies, I only use film cleaner withnpads designed specifically for cleaning film. For occasional use, a well worn, well washed and dried t shirt cut into small pieces should work.

Don_ih · Jul 14, 2023

There is also the possibility that there is some kind of glue in the qtip that's being dissolved by the cleaner and left on the film.

Dusty Negative · Jul 14, 2023

koraks said:
What kind of specs? Btw, avoiding dust & dirt usually works a lot better than trying to remove it. As soon as something has attached itself to the emulsion, it's always a challenge to remove it without leaving some kind of traces.

I'm not surprised your cleaner leaves some residue. Even 96% ethanol is still 4% water and some other stuff, a tiny part of which will be solids that won't evaporate. Moreover, whatever you smear on the film will dissolve or carry muck that happens to be on the film and deposit it somewhere else as the cleaner evaporates. You're probably seeing a combination of these factors. If it doesn't create problems with scanning or enlarging, I wouldn't worry about it too much.

For what it's worth, when I have a case of dirty negatives, I usually rewash them, optionally using mechanical removal (i.e. gentle brushing with a soft brush) if the dirt is really persistent. Especially the latter carries the risk of additional damage. Sometimes that risk is offset by the possibility of recovering negatives that are otherwise unusable. Again, prevention is a better cure.

Point very well taken, koraks, about prevention and washing rather than using solvents to clean. Chalk it up to impatience.

In fact, this might be a good reason to finally and consistently insert a dedicated fixer-remover/perma wash step in my process. I do this for prints but not usually for film.

As far as what the specks are, I assume mineral deposits but truth be told I am not sure - specks of something that an air-blower isn’t removing.

My main concern was that I was seeing residue from chemistry — fixer in the worst case. Perhaps not based on your information but yet again a reason to include a permawash step.

Dusty Negative · Jul 14, 2023

Some good points re: q-tips possibly being the source. I’ll control for that next time.

koraks · Jul 14, 2023

Dusty Negative said:
As far as what the specks are, I assume mineral deposits but truth be told I am not sure - specks of something that an air-blower isn’t removing.

I know the feeling.

For some time, I was troubleshooting a particulate matter contamination issue like yours, that mostly/only reared its head with color film and was (mostly) absent on my B&W negatives. It took me a ridiculous long time to figure out that the water cooker I was using to heat my wash water (mix boiling water with tap water to get approx. correct temperature) had scale deposits that found their way onto the film. It's a hilarious oversight looking back on it, but it had me scratching my head for a good while.

I guess the message is that it's worth tracking down contamination issues systematically. It makes the whole darkroom experience a lot less frustrating if your negatives come out reasonably clean.

Dusty Negative · Jul 14, 2023

koraks said:
I know the feeling.

For some time, I was troubleshooting a particulate matter contamination issue like yours, that mostly/only reared its head with color film and was (mostly) absent on my B&W negatives. It took me a ridiculous long time to figure out that the water cooker I was using to heat my wash water (mix boiling water with tap water to get approx. correct temperature) had scale deposits that found their way onto the film. It's a hilarious oversight looking back on it, but it had me scratching my head for a good while.

I guess the message is that it's worth tracking down contamination issues systematically. It makes the whole darkroom experience a lot less frustrating if your negatives come out reasonably clean.

I do use a sous-vide………………

koraks · Jul 14, 2023

Dusty Negative said:
I do use a sous-vide………………

Sure, but the message remains the same. Your contamination comes from somewhere; it pays to track down what the source is. It saves time & tears.

Dusty Negative · Jul 14, 2023

koraks said:
Sure, but the message remains the same. Your contamination comes from somewhere; it pays to track down what the source is. It saves time & tears.

Exactly…I’m wondering if that is what the specks are…exactly the problem you had.

koraks · Jul 14, 2023

Oh. Well, I assumed that in your sous vide setup, the water that goes through the sous vide doesn't actually touch the film. That's the way I do it, at least, but I suppose you could use the water from the heated water jacket for rinsing the film, and that would definitely introduce a contamination risk. The heating element in the sous vide stick is virtually guaranteed to be covered in scale.

runswithsizzers · Jul 14, 2023

I believe the PEC-12 film cleaner is a solvent intended to remove fingerprints and oil-based inks and adhesives without softening the emulsion.

Anything embeded in the emulsion, or stuck to it, is probably going to require a solvent which can soften the emulsion - which PEC is formulated to avoid. In other words, if your debris is not oil-based, PEC is unlikely to be helpful.

As for the residue, the company <website> says:
"If excessive amounts are applied to an emulsion, there may be a white haze left on the surface when the PEC-12 evaporates. The haze is not harmful and can be easily removed by using a new applicator with less PEC-12. (The haze doesn’t generally appear on prints, and if it appears on a slide/negative, it won’t generally print.)"

Kino · Jul 14, 2023

As Runwithsizzers suggests, you need to find out if the spots are water or chemical-based.

All water-based defects should be addressed BEFORE you use an organic solvent or it may "set" the defect in the emulsion and make it impossible to remove without damaging the emulsion.

Water-based spots usually take more water to remove and, in our experience, is simply the application of too much photoflo or stabilzer, coupled with rapid drying. Re-processing or redeveloping the film is our best option...

PEC-12 is Ethanol with N-Butyl Acetate, which is an organic solvent and it behaves much like the PerchLoroethylene we are permitted to use in our ultrasonic film cleaners. It will work wonders on oils, glues, dirt and fingerprints, but it is largely ineffective on water-based contaminants.

There is also the problem of a concentrated contaminant that is almost totally removed by an organic solvent, but it leaves a "sheen" of residue on the surface of the film. This sheen may or may not effect printing operations. We simply run the roll of film back through the cleaning machine and it often disappears. Of course, not many people have this option (including me at home), so unless it directly impacts printing or scanning, I wouldn't worry about it too much.

Dusty Negative · Jul 14, 2023

Kino said:
There is also the problem of a concentrated contaminant that is almost totally removed by an organic solvent, but it leaves a "sheen" of residue on the surface of the film. This sheen may or may not effect printing operations. We simply run the roll of film back through the cleaning machine and it often disappears. Of course, not many people have this option (including me at home), so unless it directly impacts printing or scanning, I wouldn't worry about it too much.

The “sheen” sounds like what I am seeing. Heartening to hear (if that is indeed what I am seeing) that it likely has no long-term negative effects on the film.

Dusty Negative · Jul 14, 2023

runswithsizzers said:
As for the residue, the company <website> says:
"If excessive amounts are applied to an emulsion, there may be a white haze left on the surface when the PEC-12 evaporates. The haze is not harmful and can be easily removed by using a new applicator with less PEC-12. (The haze doesn’t generally appear on prints, and if it appears on a slide/negative, it won’t generally print.)"

I did not see that. Thank you.

DREW WILEY · Jul 17, 2023

I use PEC on film with micro-fiber lens cleaning cloths. No residue. My favorite cloths are the dimpled 3M kind.

Residue from emulsion cleaner?

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