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B&W Stop Bath for RA-4
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.
"The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."
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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.
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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
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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...
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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
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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.
"The secret to life is to keep your mind full and your bowels empty. Unfortunately, the converse is true for most people."
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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.
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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
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 Originally Posted by Photo Engineer
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
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
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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
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