Pink/Magenta Stain (not blue, which is a different issue)

Discussion in 'B&W: Film, Paper, Chemistry' started by Photo Engineer, Nov 23, 2010.

  1. Nicholas Lindan

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    Sulfite has quite an effect on dye - but it seems it is the pH change that causes dyes to fade.

    Sulfite is often added to writing paper to make it “acid free”. The resulting alkaline paper can make fountain pen writing disappear.

    The effect is reversible: make the paper acid again and the color returns. Of course, then the paper rots away.

    A demonstration of the effect, using ink in water rather than paper:

    http://www.fountainpennetwork.com/forum/topic/231307-effects-of-ph-on-blue-black-inks/

    I am under the impression that Kodak HCA is buffered to a specific pH - the ‘isoelectric’ point (and here my knowledge runs out). At this pH the gelatin no longer binds to other chemicals (hydrogen bonds?) and this helps with washing out fixer and the purple dye.

    The purple dye isn’t destroyed, it just washes into the HCA - which turns a brilliant purple. Any remaining purple goes into the wash water.
     
  2. OP
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    The Isoelectric point of bone gelatin is about 4.5 and that of pig gelatin is about 9.5.

    PE
     
  3. michael_r

    michael_r Subscriber

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    ...and the pH of Kodak HCA is 7
     
  4. ericdan

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    After fixing and initial rinse, fill tank with water and let sit for 10 mins then dump. Repeat a few times or let sit longer.

    This is the only way I've been able to get rid of the dye. No fresh fixer, no longer fixing, no hypo clearing has made ANY difference AT ALL.
     
  5. williaty

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    So I'm having my own battle with what I think is the same issue. I'm using HP5+ in 120 and 4x5 sheet and running the following processing pattern:

    All steps at 20C in a Jobo CPP2 at motor speed P
    1) Pre-wash of 5 minutes
    2) XTOL 1:1 for 10'15" (120) or 10'30" (4x5)
    3) 1 minute stop in citric acid at 1g/100mL
    4) Fixing with TF-5 1:4 for 4 minutes (as per TF-5 instruction sheet for "other films")
    5) 5 quick fill/drains of the tank to wash the Jobo lift system out
    6) 6 minutes running water washed in tank (hose stuck down the central core with the lid still on) based off TF-5 instructions recommending 5min wash.

    About 50% of the time the film comes out very neutral. About 40% of the time, the film has a very light pink/magenta cast to it that's only apparent when you lay the film on top of a neutral reference. About 10% of the time the film is pink enough that it's visible when you just hold the film up in the air and look through it. Once in a blue moon, the film has a light blue tint.

    It does seem like there's a correlation between the amount of pink stain and how long the fixer has been used. TF-5 claims I should get 15-20 rolls (presumably meaning 1 135, 1 120, or 4 4x5) per 1L of working strength fixer. When I get to ~10 rolls it seems to be where I start seeing considerably more pink. This is somewhat of a problem given that I really would prefer to exhaust the fixer to make silver recovery with the Silver Magnet work properly.

    So, my questions:

    a) Does HP5+ have the problem discussed here?
    b) Am I really exhausting the fixer that much quicker than the instructions say I should expect?
    c) Is the pink stain appearing suggesting that the fixer is sufficiently exhausted to properly recover the silver?
    d) Is it more effective (in eliminating the stain) to extend fixing or extend washing?
     
  6. OP
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    Exhaustion refers to the fixing ability of the fixer. This is true for every fixer out there. The color stain may vary due to the brand or the particular size as for example 4x5 and 35mm are coated on different stocks.

    A citric acid stop is NOT recommended if you have a retained color problem. Use of an acetic acid + sulfite stop is more suited, or a sulfite bath after fixing. The new dyes used in films can be rendered insoluble based on process and water supply. Acid, sulfite and other treatments such as peroxide will eliminate the dye. Time will also cause some of them to fade. OTOH, if they are uniform, they seem to cause no problem when printing.

    PE
     
  7. williaty

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    Earlier in this thread, it was mentioned that the pink stain implies the presence of residual silver and that, even if the stain was even and caused no printing problems, you needed to remove it to ensure you had all the residual silver out. Is this true or can I just leave the pink and not care about it?

    Does the citric acid stop just not help or does it make the problem worse? I'm using citric acid because the smell of acetic acid makes me sick. If the citric is not making the problem worse, I'll continue to use it. However, if it makes the pink dye harder to remove, I'll have to just switch to a water stop instead.

    Someone gave me a 5lb jar of Sodium Sulfite from Photographer's Formulary. I've never had any clue what it's good for. If I kept my processing routine the same but added a sulfite bath between the fixer and the wash, what dilution should I use (in terms of g/L) and how long should I let it stew?

    Thanks!
     
  8. OP
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    Some colored materials can form salts with some acids. Citric acid is one of them. It is due to the solubility of the citrate salt and the molecular weight.

    Sulfite is used to enhance removal of residual hypo from films and papers and it also reacts with some dyes.

    The pink stain is NOT related to retained silver, but to reassure yourself, use the retained hypo kit and the retained silver kit available from several sources.

    Many of your questions are quite basic and suggest that you should do a bit of reading up on processing films and papers before you have a problem.

    Acetic Acid is vinegar. It is used at about 2% whereas many vinegars are sold at up to 5%. Don't try mixing acid with Sulfite or you really will have a smell that you don't like. Go careful and easy in this.

    PE
     
  9. williaty

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    Taking your points one at a time:

    So the summary is "Yes, citric acid as a stop could be making the pink stain harder to wash out, so stop that".

    I was taught in university not to use any sort of HCA, so I never had any reason to lean that HCA was mostly sodium sulfite, hence having no idea what the jar of sodium sulfite was for. Older threads suggest that 20g/L of sodium sulfite used once and dumped makes a fine clearing agent for film and paper, but I'm not seeing a recommendation for time.

    If you say the pink stain has no problems with long term stability of the film, I'll take your word for it.

    Yeah, I have little to no interest in the chemistry of photography beyond what I need to get work done. The only time I take a hard look at it is when I have a problem like this. Otherwise, I just carefully follow what the instructions say to do and acknowledge that the professional photochemists like yourself are going to be better at writing instructions than I will be at doing chemistry.

    I'm aware acetic acid is vinegar. I HATE vinegar. I can't stand anything cooked with it or made from it. Like I said, the smell of acetic acid makes me sick.
     
  10. OP
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    Well, I am not an advocate of HCA, but in your case, if you insist on removing the stain, then Sulfite should do the trick. Exposure to sunlight might also work as some have reported. I would use the Sulfite solution and watch for the stain to begin vanishing. Then I would treat the film for another 5 minutes or so until it is evenly gone. Then a 10 minute wash should be necessary along with a treatment in Photo Flo.

    PE
     
  11. ericdan

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    All the stop baths I see available here are citric acid. Ilfostop or Adostop for example.
    Which one is an Acetic Acid example?
     
  12. OP
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    In Japan? IDK. Ask at a photo store I guess.

    Sorry.
     
  13. ericdan

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    It must be this stuff I guess.
    literally translated to: Fuji Acetic Acid
    So Acetic Acid smells more than citric acid but does a better job at stopping development?
     
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  15. OP
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    Acetic acid is vinegar. Vinegar is about 2 - 5% acetic acid. Acetic acid itself is sold in 28% and "glacial" which is about 98% + pure.

    It smells like vinegar and is much more acidic. Stopping is much more rapid. I have been told that citric acid must not be used with color products. I've forgotten the reason. My comments above may relate to that, but it has been years since I was told that.

    PE
     
  16. ericdan

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    Interesting. This Fuji bottle says 50%. What percentage do you use as working solution?
     
  17. OP
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    I use 1 - 2% made from either 28% or Glacial.

    PE
     
  18. ericdan

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    Tri-X will be steal grey and flat as a pancake if you let it sit in plain water for 60 - 90 mins after developing.
    Not sure if that is bad for the base or emulsion.
     
  19. ericdan

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    The stain also seems to fade unevenly with time. Two year old Tri-x.
     

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  20. Gerald C Koch

    Gerald C Koch Member

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    It's probably best to limit the wet time for film to a minimum. The magenta stain is not going to harm anything.
     
  21. bence8810

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    I - like Eric - just soak the films. Only with Kodak I have this purple stain and while I didn't care in the beginning (and have a lot of purple negatives) I started soaking the films for 20-30 minutes after the Ilford wash (5-10-20-40 inversions and a fresh water change in between).
    The result is always a perfectly clear roll of film. I am happy with this result, especially that it doesn't waste extra water.

    Ben
     
  22. ericdan

    ericdan Subscriber

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    check my photo above. It fades unevenly on the negative. I assume that will certainly have an effect. Scanning or enlarging.
     
  23. OP
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    I discussed this with a former EK engineer and one of the inventors of the layered dye technique which seems to be the culprit here. It was not a problem at one time, so if it is one now and getting worse, I suggest that there be a conversation between customers and Kodak. But, there appears to be a solution such as the long wash Ben mentions above and others I have heard such as soaking in Sodium Sulfite solution.

    PE
     
  24. williaty

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    It may be worth noting that my problem was completely resolved by switching to two-bath fixing. No extended wash times, no additional clearing step, just 2 bath fix and then straight into a wash.

    Interestingly, the 1st fix bath comes out barely tinted pink while the second fix bath comes out electric neon Barbie pink. I've never seen something like this before where the majority of the chemical to be removed "washes" out in the 2nd bath. I also find it interesting that the pink color in the fixer vanishes by the time I use the fixer again a few days later.
     
  25. OP
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    The dye is rapily destroyed by sulfite and oxygen both. It can be oxidized and reduced depending on conditions.

    PE
     
  26. ericdan

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    That is very interesting indeed. I use fresh fixer dilution pretty much every time, but only one fixer bath of 5-6 minutes.
    I haven't noticed that removing the dye. I'll see if a two batch approach makes a difference. Would be nice to cut down on the soaking and washing time.
     
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