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  1. #11

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    Well, while Thornton's heart may have been in the right place, when I tested a lot of these things I found the chemistry logic to be flawed, or at the very least, overcomplicated for no reason. I'm picking on Thornton here because that was the topic, but it's really two-solution Metol-sulfite-alkali development in general where there is much confusion and conflicting information on everything from which alkali to use, to agitation etc, etc. As Grant Haist points out, scientific studies on true two-bath development are scarce, and the situation is even more nebulous when it comes to two-solution Metol-sulfite-alkali development. I've seen virtually no good data, testing, or even sound theory for what most people say.

    Suffice it to say before changing the formula, I would first start by reducing the amount of time in solution A. You'll have to experiment to see what gets you the right contrast/speed balance.

    Also, another flaw I've found in the vague instructions regarding solution B in general, is that frequently the time is too short, and the effects of agitation are not well documented. This depends on the pH and buffering of solution B, as well as the film type.

    My view on this type of development from a sensitometric perspective is this: the aim in most cases should be to develop is little as possible in solution A, but for enough time that the emulsion becomes saturated with developer, and then to develop in solution B until exhaustion. This maximizes the benefits of this type of process: (a) a long, straight curve, (b) lower than normal contrast, (c) retention of film speed.

  2. #12

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    Quote Originally Posted by Michael R 1974 View Post
    Well, while Thornton's heart may have been in the right place, when I tested a lot of these things I found the chemistry logic to be flawed, or at the very least, overcomplicated for no reason. I'm picking on Thornton here because that was the topic, but it's really two-solution Metol-sulfite-alkali development in general where there is much confusion and conflicting information on everything from which alkali to use, to agitation etc, etc. As Grant Haist points out, scientific studies on true two-bath development are scarce, and the situation is even more nebulous when it comes to two-solution Metol-sulfite-alkali development. I've seen virtually no good data, testing, or even sound theory for what most people say.

    Suffice it to say before changing the formula, I would first start by reducing the amount of time in solution A. You'll have to experiment to see what gets you the right contrast/speed balance.

    Also, another flaw I've found in the vague instructions regarding solution B in general, is that frequently the time is too short, and the effects of agitation are not well documented. This depends on the pH and buffering of solution B, as well as the film type.

    My view on this type of development from a sensitometric perspective is this: the aim in most cases should be to develop is little as possible in solution A, but for enough time that the emulsion becomes saturated with developer, and then to develop in solution B until exhaustion. This maximizes the benefits of this type of process: (a) a long, straight curve, (b) lower than normal contrast, (c) retention of film speed.
    Thank you very much this is very helpful. This weekend I'll go out and shoot a few rolls and try experimenting with the time in Bath A.
    "The key to immortality is first living a life worth remembering." - Bruce Lee

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  3. #13

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    Quote Originally Posted by baachitraka View Post
    May we know when to consider it is a dense highlights and blown highlights in stops from shadow?
    It isn't a matter of stops. It is a matter of local contrast. Local contrast = detail. A blown highlight means there is no detail in the negative, meaning there is no contrast in the highlight. This can be an issue with severe contractions or compensating procedures. It may seem counterintuitive at first, but excessive contrast reduction can result in more blown/blocked highlights than when developing to normal contrast.

    A dense highlight may not print straight, but there might still be good local contrast (detail) in the negative. So you use printing controls to bring those dense highlights onto the paper.

  4. #14

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    Quote Originally Posted by MrBrowning View Post
    However Barry Thornton in Edge of Darkness suggests changing the amount of Sodium sulfite (if memory serves) for N- or N+ development.
    I believe rather than sulfite, he suggested varying the concentration of sodium metaborate within a range. Varying the alkali concentration is a fairly common recommendation for changes in contrast and speed. I have not found this to be a very effective control.

  5. #15
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    ...thats 8g, 12g and 20g of sodium metaborate for -N, N, +N
    Last edited by baachitraka; 06-19-2014 at 09:44 AM. Click to view previous post history.
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  6. #16

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    Quote Originally Posted by Michael R 1974 View Post
    I believe rather than sulfite, he suggested varying the concentration of sodium metaborate within a range. Varying the alkali concentration is a fairly common recommendation for changes in contrast and speed. I have not found this to be a very effective control.
    Thank you for the correction. I'm at work and apparently I had it switched in my head.

    Quote Originally Posted by baachitraka View Post
    ...thats 8g, 12g and 20g for sodium metaborate for -N, N, +N
    Thanks for that.
    "The key to immortality is first living a life worth remembering." - Bruce Lee

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  7. #17
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    For me it was not so much of fun with two bath, in-fact it was a pain. Life became much easier after I switch to D-23 1+1. Just my story...

    Other experiment that my be interesting is Divided D-23. Either use borax or sodium metaborate or sodium carbonate in second bath for varying contrast and grain.
    OM-1n: Do I need to own a Leica?
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  8. #18

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    Quote Originally Posted by baachitraka View Post
    For me it was not so much of fun with two bath, in-fact it was a pain. Life became much easier after I switch to D-23 1+1. Just my story...

    Other experiment that my be interesting is Divided D-23. Either use borax or sodium metaborate or sodium carbonate in second bath for varying contrast and grain.
    DD-23 is something that I plan on trying but haven't yet. It's on my to do list after I have a better understanding of BTTB.

    I find that I like using the two bath more than I did using a single bath developer. I'm not sure why maybe I just like the results better than what i was using before.
    "The key to immortality is first living a life worth remembering." - Bruce Lee

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  9. #19

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    It tends to give a different curve shape. Image structure characteristics can also be different. My guess is you won't find a difference between DD-23 and Thornton's, which is just a slight modification of Dalzell's version of the Stoeckler A bath (which is nearly D-23).

  10. #20
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    One reason I stay away from 2-bath is that I find that I always need to bring the developer temps to 20°C which is rather boring to do.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.

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