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  1. #1
    Donald Qualls's Avatar
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    Vitamin C in divided developer?

    I'm aware that ascorbic acid (or erythorbic acid, for that matter) can't be preserved in developer working solutions by sodium sulfite -- it's a more active antioxidant than the sulfite. However, it just occurred to me, while reading the thread on Split D-23, that I'm not sure how Vitamin C holds up in a neutral to acidic divided stock solution.

    Does anyone know, can I make a water based concentrate or stock solution of or containing ascorbic or erythorbic acid and have it keep long enough to compare to conventional developers? Or is it going to go off on me in a few hours or days? Yes, I know there are non-aqueous concentrates (like PC-TEA); I'm interested in the possibilities for a divided developer using vitamin C or equivalent.

    And if no one knows, I can test, but I thought I'd save myself a dollar's worth of vitamin C if someone knows it won't work...
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  2. #2

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    It is not true to say that sulfite does not function as a preservative in ascorbate developer solution. In my testing, oxidation and loss of ascorbate in developer concentration sharply increases when much of the sulfite is lost by oxidation.

    If you don't do anything special to preserve ascorbates, it is more likely that the ascorbate solution dies sooner in more acidic stock. I don't recommend acid stock solution for ascorbates.

    If you are trying to make a two bath developers, I should also note that the first bath should be weakly alkaline, like pH of 7.5 to 8.3. Acidic first bath would not develop the film enough, even if the second bath is fairly alkaline. Some of the popular developer books contain misconception on this issue.

    There's a way to make ascorbate developer last long. See my DS-12 film developer and DS-14 print developer. They last long enough to be practical. DS-10 is a very good fine grain film developer, but it should not be kept for more than a couple of weeks, as I've seen cases where developer went off after that period. Effort to improve this is ongoing.

  3. #3
    Maine-iac's Avatar
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    Quote Originally Posted by Donald Qualls

    Does anyone know, can I make a water based concentrate or stock solution of or containing ascorbic or erythorbic acid and have it keep long enough to compare to conventional developers? Or is it going to go off on me in a few hours or days? Yes, I know there are non-aqueous concentrates (like PC-TEA); I'm interested in the possibilities for a divided developer using vitamin C or equivalent.

    And if no one knows, I can test, but I thought I'd save myself a dollar's worth of vitamin C if someone knows it won't work...

    Interesting you should ask this just one day after I experimented with dividing my tried-and-true Phenidone/Vitamin C/Metaborate developer. In a word, it didn't work. Perhaps Ryuji's answer gives me a clue where to go from here, but I just did a simple experiment: exposed two rolls identically, and developed them for two different developing times, one at three minutes in each bath, and the other at six. Neither roll had a visible image--- just clear film.

    I put the Phenidone/Vitamin C in bath A and the metaborate in Bath B. I should have tested the pH of Bath A but forgot to do that. I have used divided D-76 and divided D-23 many years ago, but hadn't tried it since I began using my current PCM soup.

    Larry

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    I don't know the answer to Donald's interesting question.If air is excluded I don't see why a concentrated PC part A solution should not be stable.A solution with no sulfite might preserve the edge of grain sharpness which is a limitation of the 2 bath developer I sometimes use.

  5. #5
    Donald Qualls's Avatar
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    Quote Originally Posted by Ryuji
    If you are trying to make a two bath developers, I should also note that the first bath should be weakly alkaline, like pH of 7.5 to 8.3. Acidic first bath would not develop the film enough, even if the second bath is fairly alkaline. Some of the popular developer books contain misconception on this issue.
    Okay, this throws my thinking directly into a cocked hat...

    It's been my understanding about true two-bath developers like Diafine, Stoeckler, and SD-4/SD-5, that little or no development takes place in Bath A, and (at least with Diafine) contamination of Bath A with the alkaline Bath B results in destruction of the developer (or at least its special properties). Or are you saying that an acidic carry over would reduce the pH of Bath B enough to prevent adequate development in the second bath? I think I can beat that, if that's the problem, by one-shotting Bath B, which is inexpensive anyway (both borax and sodium carbonate are much less than a dollar a pound in technical grade)?

    Either way, a mildly alkaline Bath A isn't a problem, except I presently have no means to test pH and ensure it's only *mildly* alkaline -- and if it's more alkaline, too much development will take place in Bath A and I'll get something more like DD-23 than, say, DD-76. I suppose I could add tiny amounts of bicarbonate or carbonate until no foaming occurs; a sort of titration, using gas evolution as the indicator.

    I know there are ways to preserve ascorbate in solution -- XTOL has been doing it (with varying success that I understand was eventually traced to packaging problems) for some years. What I was hoping for, however, was a developer that, like Diafine, I might be able to keep in good bottles, use when I need it, and reasonably expect it to still be good a year or two years later if I haven't just used it up. From what you're saying, it sounds like mildly alkaline solution with lots of sulfite is the right direction.

    Of course, there remains the option to mix the 2-bath developer immediately before use; less convenient than having the two solutions in bottles, but it won't go off in minutes, and it would be easy enough to premeasure the dry chemicals into packets that could be mixed in the time it takes to open a bag and pour the contents and water into a graduate. Seems wasteful, but not really any more so than what I'm using now for the applications I have in mind.
    Photography has always fascinated me -- as a child, simply for the magic of capturing an image onto glossy paper with a little box, but as an adult because of the unique juxtaposition of science and art -- the physics of optics, the mechanics of the camera, the chemistry of film and developer, alongside the art in seeing, composing, exposing, processing and printing.

  6. #6

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    Donald,

    Several years ago, I had already been preparing my Gainer developer (this was before the PC-TEA and PC-Glycol era) in two baths, one stock solution containing the phenidone and ascorbic acid and the other containing the alkali. In normal use, I would mix them 1+1+8 with water before use. (I can dig up the formulas if you are interested.) They kept fairly well for several months but the developer stock gradually turned yellow over time. I didn't check the yellowed developer for activity, but instead just dumped it.

    I once tried to "do a Diafine" on the Gainer developer by soaking my film in the developer solution (without alkali) for several minutes, followed by the activator solution. I got clear film and I didn't pursue it further (either the developing agents didn't soak into the film or the carry-over neutralized the activator, as Ryuji mentions).

    The two-bath method does work, but now I just use PC-Glycol (the developing agents are dissolved in propylene glycol and diluted into aqueous sodium carbonate just before use). My stock solution is two years old and is still very active.

  7. #7

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    This will blacken a film leader,it is not suggested for films.

    Part A - 1/4tsp phenidone in 50ml isopropanol,take 10ml of this add to Vit C 1tsp in 50ml water.Soak film leader for 3 min-no color change.

    Part B -3tsp sodium carbonate monohydrate in 500ml water.Remove film leader from part A and soak in part B for 3 min - goes black ,not very high density.

  8. #8

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    The problem is that, when you are reading popular darkroom bibles, you don't know how much of the stuff is oversimplified for the audience the authors assumed. If you give your reading too much confidence without tracing back to all the original research reports, you'll face problems.

    Contrary to what's written in common darkroom bibles, two bath development is not like mixing bath A and bath B in the emulsion layer when the film is transported. I do not know of a successful two-bath developer where film is not developed at all in bath A.

    In the history of developer technology, two-bath method was studied c. 1930 as a way to minimize chemical waste for motion picture processing. However, research at that time already found that the approach is not very fruitful. The same goal was achieved by replenishing method. If you are worried about chemical cost, this is the way to go. I used to do it with hand inversion tank, and I got pretty reliable results. I could even save developer solution between uses.

    Measurement of accurate pH is kinda essential if you do research work in developer chemistry. But this is a lot more than buying a meter, because pH probe is a high maintenance instrument. So I don't know what to tell you on this one. You might want to decide between letting skilled people do the research, or to become the skilled person yourself to do the task.

    Using bubbling as an indicator is very unreliable. You should at least get fine grain pH test strips (they come in narrow window of pH range so you need a few different sets). You also might want to get a few pH indicator dyes for different pH ranges. For usual darkroom work, these are often sufficient.

    Making ascorbate solution that keeps is not a trivial task. You should search for patent literature, for example. There are numerous inventions for which patents are granted but very few are used in actual commercial products. This is because many inventions obtained from hard work at major manufacturers are also ineffective or not cost-effective enough. I also do try to replicate some of their techniques to see ho wthey work, but some of them don't even work! I have good sense of what is going on in this area but it involves a few branches of chemistry (electrochemistry, coordination chemistry, organic chemistry, etc.) and it's not really a topic for amateurs lacking good background in these areas. A lot of known tricks for MQ or PQ developers do not work with ascorbate developers.

    Ascorbate and reductone developing agents are known since c. 1930, but they haven't been used for practical applications until last decade. Even that was partly pushed by environmental regulations. What this tells you is how hard it is to make practical, reliable developers using this agent.

  9. #9

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    I have also tried making divided ascorbic acid developers, both for paper and film. It didn't work. It may be because the acidic oxidation products of ascorbate inhibit the reaction too quickly. Hydroquinone would be the way to go if you're making a divided developer.

  10. #10
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    Let me ask about the absorbing of the first part in the gelatine. Many years ago I had no difficulty reticulating Tri-X and other films of the time. Nowadays it is difficult to reticulate most BW films. Then, too, I seem to remember that acidic solutions are not conducive to absorption.

    An ascorbate developer need not be acidic to be practically inactive. A combination of phenidone and sodium ascorbate may basic enough to allow absorption into the gelatine without being basic enough to do appreciable development in the first bath. I'm just speculating. A possibility, beside those that Ryuji has suggested, is a phenidone-ascorbic acid solution in propylene glycol with a small amount of TEA enough to make it just a little on the basic side when it is mixed with water.
    Gadget Gainer

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