How to clean calcium spots off old film?

[lukitas]

I have a binder or two of 20 and 30 year old 35mm negatives, which I developed and rinsed in the local tap water. The water is rather high in calcium and calcium carbonate, and it left loads of very small white spots, sometimes as many as a starry sky, often not much bigger than a pixel on a 4500x3000 pixel scan.

I'm thinking of soaking the negatives in a vinegar solution, so that any chalk can just dissolve in the acid, leaving the emulsion clean.
I would then rinse in distilled water (maybe with a little surfactant), and hopefully get them to dry without more dust spots. (Thinking of steaming up the bathroom, before hanging them behind the shower curtain)

I'm pretty sure a stop bath won't do any harm to the film, but will it be enough to dissolve the calcium? Has anyone an idea of what concentration, which acid, how much soaking time? Could I damage the emulsion doing this?

I'd be very grateful for any pointers.

 

[mbisc]

Best of luck on this one! Sorry I can't provide any help, except that maybe you can start with a meaningless strip of film, a relatively high concentration of vinegar (something like 50/50) and a long time (say, an hour) and see if it removes the gunk and/or damages the emulsion...

 

[lukitas]

I may well have to try that, as nobody seems to have any experience with this problem.

I've read somewhere that fixing too long can leach silver out of an emulsion.
Would this be the case with a diluted acid bath?

I'll have to try, but I'd like to know more first.:bang:

 

[Highway 61]

I'm thinking of soaking the negatives in a vinegar solution, so that any chalk can just dissolve in the acid, leaving the emulsion clean.
I would then rinse in distilled water (maybe with a little surfactant), and hopefully get them to dry without more dust spots. (Thinking of steaming up the bathroom, before hanging them behind the shower curtain)

This is exactly what you should do. After the acid soaking, rinse for long enough under tap water then have the film rest for a while into distilled water with wetting agent.

Acetic acid at 2% will do it fine. 50-50 vinegar-water will make it for a 4%, a bit too harsh maybe. So, go for 25 vinegar-75 distilled water.

Steaming up the bathroom is perfect.

 

[L Collins]

PEC-12 Archival Photographic Emulsion Cleaner. B&H carries it.

Spritz on, wipe off.

 

[Jani_from_Finland]

Photo-flo 200 or other Wetting agent?

 

[lukitas]

PEC-12 Archival Photographic Emulsion Cleaner. B&H carries it.

Spritz on, wipe off.

Scared to death of wiping scratches in my emulsion.
If I read the product description right, PEC-12 handles non-water-soluble chemicals. So it wouldn't be good for chalk.

Thanks for the hint though.

 

[lukitas]

This is exactly what you should do. After the acid soaking, rinse for long enough under tap water then have the film rest for a while into distilled water with wetting agent.

Acetic acid at 2% will do it fine. 50-50 vinegar-water will make it for a 4%, a bit too harsh maybe. So, go for 25 vinegar-75 distilled water.

Steaming up the bathroom is perfect.

Thanks, at least I am on the right track.

How long should I soak? For a stop bath, a quick rinse is fine, but for hard chalk, I think a bit longer would be better. 5 minutes? Half an hour (like a coffee-machine)?

 

[Chris101]

Vinegar or stop bath would work, don't soak for longer than 5 minutes - this will be well long enough to dissolve any CaCO3. Agitate during the soak. Then wash the film, the same as you would after developing, and finally treat it with a wetting agent, and hang to dry.

I have done this.

Good luck!

 

[Jani_from_Finland]

I think a bit longer would be better. 5 minutes? Half an hour (like a coffee-machine)?

May not be related, but kind of.
I find that nowadays i do the rinse after fix rather 5' instead of the old long washes to be better. I would try to take a slow approach and try with shorter times just to be safe, you can always do the procedure again at 20% or 50% or 100 or 200 etc.

 

[lukitas]

Thank you all, and Highway 61 and Jani most especially.

I now have a decent framework to work in. Thanks again.

 

[Borge H]

I use ethanol. I quickly wipe the base side (no emulsion) with a clean cloth wet with alcohol used for fuel or cleaning on my dry negatives.

Then I can scan them or enlarge them with no problems!

But it is best to add some liquid cleaning (disk washing) in the last rinse to prevent the stains.

Problem solved!

 

[Jani_from_Finland]

My fellow had issues with calsium from the tap water in his house on Fomapan and maybe efke films, i had issues also with fomapan, i was not using any wetting agent at that time neither did he (we both was starting self dev at the time). After i started to use Photo-flo 200 and Rolleis Super HCA (1:1000) i never had this problem again. I have sometimes rewashed films that got dirty in the photoflo and they was as good as new after that. Stab should be the same thing also.