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  1. #1

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    Capacity of C-41RA bleach used to exhaustion (one-shot)?

    For the small amount of film I now process, I've switched from C-41 to the C-41RA process. The RA process uses faster bleach and fixer solutions, for a total process time of about 8 minutes.

    I am using the solutions one-shot in a Jobo. The "RA" bleach is extremely expensive (though the Trebla version is slightly cheaper than the Kodak). This is probably because its replenishment rate is 1/10 that of the standard Flexicolor Bleach III (5ml per roll rather than 52ml). In fact, the replenishment rate is so low it approximates the amount of solution lost by carry-over into the fixer in a tank system, though it might not in a large dip-and-dunk.

    Kodak's process documentation does not give a one-shot capacity for the RA bleach or fixer -- it gives only the general advice that the capacity of bleach and fixer solutions used to exhaustion in is twice that of the developer.

    I am sure the capacity of the RA bleach used this way is not 10 times that of the standard bleach, but what is it? I know with small solution volumes capacity can have as much to do with build-up of byproducts and carry-over from the previous process step as with exhaustion, but I would hope I could, for example, reuse a tank of bleach at least twice, or use minimum volumes to cover the film with my (carefully-leveled) Jobo processor and tanks. By the replenishment rate (5ml per roll) both practices look like they should be just fine, but by Kodak's "twice the developer" instructions they are not.

    Opinions? I could call 800-242-2424, but I wonder if there is still anyone there who knows enough to help me when the written documentation can not.

  2. #2
    hrst's Avatar
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    It is a bit unclear to me what do you mean by "one-shot capacity". One-shot means, you use it once . Of course, you can use it replenished, and if the rate really is 5 ml per roll (!), it will be very cost effective.

    But do you mean by your question that you would want to reuse it without replenishing? In this case, it is a bit hard to approximate exactly how many times are ok. I think that with a replenishment rate that low, it would be so many times that the real concern in a Jobo is dilution and contamination from the developer. That is why I wouldn't reuse anything more than 4-6 times, or if I replenished, I would replenish it by replacing 15-30% of the solution every time; overreplenishment for bleach is not a problem.

  3. #3

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    Quote Originally Posted by hrst View Post
    It is a bit unclear to me what do you mean by "one-shot capacity". One-shot means, you use it once . Of course, you can use it replenished, and if the rate really is 5 ml per roll (!), it will be very cost effective.

    But do you mean by your question that you would want to reuse it without replenishing?
    I'd like to use the solution to exhaustion. Kodak has recommendations for this in the rotary-tube section of the main flexicolor document, but they don't make separate recommendations for the RA and standard bleach or fix.

    So, what I'd really like to do is a modification of what I'm doing now:

    What I'm doing now:

    * Take 1000ml of solution from the bleach stock bottle. Use it for two successive batches of 5 rolls of 135-36 film, which roughly corresponds to Kodak's recommended capacity (since I use 1000ml of fresh developer per batch, using the developer one-shot).

    It would be nice to know whether in fact I can extend this reuse to 4, 5, or 6 batches; since that would reduce my costs by 1/2 to 2/3, the RA bleach being by far the most expensive component of the process.

    * Minimum solution volume for the Jobo reel tanks I'm using is 640ml. It'd be nice to know whether I can use 640ml twice to do two batches of 5 rolls each.

    It strikes me that if carryover is a big issue, trying to "replenish" with 5ml per roll (25ml per batch) may be very questionable unless I maintain a very large "working solution" volume, too, perhaps an entire 5L bottle of bleach, with a separate 5L bottle as fresh replenisher. Keeping 5L of bleach at C41 working temps in a Jobo is kind of a pain.

  4. #4

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    It never wears out... (or so it seems)

    From my experience with regular C-41 bleach from Kodak, bleach just doesn't exhaust, basically. I am on I think the 6th or 7th time around with the same set of 5L of bleach. I think I've processed at least 260-300+ rolls of 120 in it so far. I've used the Kodak bleach regenerator product each time, which regenerates it somehow. It's still looking great and the negs look and print fine.

    If anything, it sounds like the C-41RA bleach is "stronger" than the regular bleach. I'd think then it could be reused indefinitely, like the regular C-41 bleach.

    -Ed



 

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