B&W Stop Bath for RA-4

Discussion in 'Color: Film, Paper, and Chemistry' started by Snapshot, Apr 23, 2007.

  1. Snapshot

    Snapshot Member

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    Hi All,

    I have a question with regards to using a stop bath for RA-4 print developing. Are there any issues with using a stop bath normally used for B&W prints (e.g. Kodak Stop Bath with Indicator) for RA-4 prints? In other words can I use the stop bath for B&W and colour or should I mix a separate batch for each type of print. I'm worried about amassing different chemicals and the effect it may have on the final print.

    You input would be appreciated.
     
  2. PHOTOTONE

    PHOTOTONE Member

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    I wouldn't recycle the stop bath between RA-4 and B/W. But you should be able to use similar, if not the same acetic acid dilution for each. I see no need to use indicator stop bath for color. a simple acetic acid (diluted, of course) bath would be fine.
     
  3. Photo Engineer

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    I have used Indicator stop bath for both B&W and color. I thought, at one time, that the indicator might stain color, but it does not.

    However, I advise caution in mixing processes with one stop. I have done it, but I have never tested whether there are any extended bad effects.

    PE
     
  4. percepts

    percepts Member

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    dyes are chemically faded by acid. Acid stop bath and paper with dyes in it are a big no no. That is why colour processes are all alkaline. Use your stop bath at your peril...
     
  5. Photo Engineer

    Photo Engineer Subscriber

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    Percepts;

    Sorry, but you are wrong. Kodak recommends use of a stop with the RA4 process, and the stabilzers used with color paper were pH 3.5 and 4.5 respectively for the two once used.

    Use the stop bath between Developer and Blix for more uniform stopping of development, especially in drum processes.

    Stop can also be used in the C41 process.

    I might add that the blix and bleach and fix are about pH 6.5 for both processes.

    PE
     
  6. Snapshot

    Snapshot Member

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    It seems my concerns were valid. I'll use separate stop baths for B&W and RA-4. It's not like it's very expensive.
     
  7. percepts

    percepts Member

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    I stand corrected but I might add that the PH levels used by agfa are much less acidic towards the neutral. If you do use acid stop, then make sure it is at the correct dilution.
     
  8. Photo Engineer

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    Well, the function of acidic steps in color processing reduces pink stains on keeping. Color developer tends to stay in coatings, trapped in the organic solvents. Therefore, acid stops tend to extract the p-phenylene diamine developers as they are alkaline and the acid makes a ppd salt. So, acid is good, but not below pH 4.5 or so. Actually, 2% acetic acid or Indicator Stop bath are just fine.

    So, the stop bath helps uniformity in processing by stopping development, and it also evens out chemical retention by bad processing (improper washing) that sometimes happens.

    The color developers contain carbonate, and the combination makes sodium acetate in the stop which actually works quite well in moderating the pH drop. Even so, the film or paper will fizz, but you won't get pinholes. Oh, I've said that already elsewhere......

    Anyhow, the stops I mention work well.

    IDK much about the Agfa process, but it might be so to avoid patent issues. IDK. We found 6.5 for bleach, fix and blix to be optimum.

    PE
     
  9. chorleyjeff

    chorleyjeff Member

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    I have just read again the Fotospeed CKRA4 processing kit instruction, for RA4 paper at 35c. They say for Kodak papers use a 5% solution and 2% for all others except Fuji for which it says use no stop bath ie go straight from developer to blix.
    Question is why no stop for Fuji? I should add that I use Fuji CA without stop bath in a Nova slot processor with no staining problems - I replenish at the same rate as the developer. Also what difference would it make using stop with Fuji CA?
    Cheers
    Jeff
     
  10. Photo Engineer

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    The Kodak paper does not need a stop either. It can be used in case you see uneven stains. This arises from the blix in rotary processors, but not AFAIK anywhere else.

    The stop always helps. I use 2%. That is what we used at Kodak. OTOH, the kit you have may have a more alkaline developer, IDK.

    PE
     
  11. Jerry Basierbe

    Jerry Basierbe Member

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    I've been using Kodak indicator stop at 2% for a few years and haven't seen any problems. I have seperate bottles for color and b&w use.

    Jerry
     
  12. pentaxuser

    pentaxuser Subscriber

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    Jeff. I was doing a search on Fotospeed papers actually when this thread came up. Did you ever get an answer on why no stop with Fuji and Fotospeed RA4

    I have never used Fotospeed RA4 but was considering it and I have Fuji paper for which i have always sued a stop with other RA4 chems such as Tetenal and Paterson. I rotary process and wonder about not using stop because of what PE says and the reduced life of blix without a stop bath?

    If Fuji is OK with stop for other RA4 chems I wonder what makes Fotospeed NOT OK with stop for Fuji RA4 but OK for other chems.

    My reasoning is: If Fuji paper is OK with stop for other RA4 chems then it can't be anything in the Fuji paper. On the other hand if Fotospeed RA4 chems need or at least can use stop with other than Fuji then it can't be the peculiarity of Fotospeed chems. If it was you'd think that Fotospeed would say not to use stop with any paper

    OR is there an explanation that reconciles this? Assuming of course that Fotospeed haven't just got it wrong.

    These days I wonder who the other papers( not Fuji or Kodak) would belong to?

    Thanks

    pentaxuser
     
  13. Photo Engineer

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    The use of a stop bath with RA papers is dependant on the pH of the Blix. Since most RA blix baths are about pH 6.5 for stability and activity purposes, a stop is sometimes useful especially with drum processes.

    With a tray process I seldom find a need for a stop.

    PE
     
  14. max_ebb

    max_ebb Member

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    I do drum processing for RA4 (temperature controlled at 95°), and I find that plain warm water works just as well as a stop bath.
     
  15. Photo Engineer

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    For those interested, the color developer is absorbed into the coupler solvent droplets. Incomplete or exhausted blix or incomplete washing will leave some of the CD3 in the droplets which will cause a slightly pink stain that slowly vanishes, or it will slightly degrade the dye stability. This is a tiny change which varies depending on retained CD3.

    The current process, when well run, will remove all of the CD3 without a stop, but a stop is positive assurance that it is all removed if the process is marginal for any reason.

    So, this is another reason why I use a stop.

    I said above that I seldom found a need for a stop with tray processing. This is due to the better agitation and the single sheets. A drum process is less efficient in washing prints. I find that with my drum, I have to use a supplemental wash to remove all residual blix coloration from my prints.

    PE