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  1. #71
    Maine-iac's Avatar
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    Quote Originally Posted by gainer View Post
    I have found that a small amount of ascorbic acid in, say, a Metol-hydroquinone solution seems to be capable of at least as much superadditivity as the MQ solution with sulfite. It will be a staining developer if used without sulfite, as would the combination of Metol-pyrogallol-ascorbate or Metol-catechol-ascorbate, or p-aminophenol-catechol-ascorbate. I only know these things from experiment.
    Pat,

    I've never tried using Vitamin C with an MQ developer for film; I have used it in paper developer concoctions, where the staining doesn't appear to happen. I'd be interested in trying it with film. What proportions of M, Q, and C do you use? What activator--carbonate? metaborate? borax? How long?

    Larry

  2. #72
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    If you are interested in the stain, use the Pyrocat MC formula with hydroquinone instead of catechol.

    You could use 2 grams of Metol, 5 grams of hydroquinone, 5 grams of borax, and 10 grams of sodium ascorbate to make a liter of working solution. It's D-76 minus sulfite plus ascorbate. If you don't have ascorbate on hand, mix 2 teaspoons of ascorbic acid and 1 teaspoon of sodium bicarbonate (baking soda) in a couple of ounces of lukewarm water and add it to the mix when the effervescence subsides. Treat it like D-76 and see what happens.
    Gadget Gainer

  3. #73

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    The last week or so I have been experimenting with ortho litho film developed using dilute rodinal solutions modified with the addition of borax and sodium ascorbate. I used 400ml H20, 1/8 teaspoon borax, and 1/2 teaspoon sodium ascorbate. (Sorry for the mix of metric and non-metric measurements.) To this I added either 1ml or 2ml Rodinal.

    I shot some scenes in the back yard on 4x5 film and developed two sheets together in a batch.

    Just based on the look of the negatives and preliminary testing it seems that the 1ml Rodinal solution will give a graded contrast range if I rate the film at an EI of somewhere in the neighborhood of 1/4 to 1/8 and develop the film in the range of 6 minutes at 75 F with continuous agitation in a rotary processor. The 2ml rodinal solution seems just a bit too active. (In fact, 6 minutes of the 1ml solution might even be a bit too much development.)

    I haven't tried doing many controlled densitometry measurements yet, but I might eventually.

    Anyway, what makes these observations relevant to the present discussion is that 1ml of rodinal is not much developer, being just a fraction of the amount recommended to avoid developer exhaustion. Therefore, it would seem that such a small amount of developer would risk exhaustion, particularly at a Rodinal dilution of 1+400. However, I don't think that exhaustion was taking place. In fact, fully over-exposed film gave a Dmax of something like 2.4 (as I recall) using a densitometer, so I don't think there is any developer starvation going on. I presume that the ascorbate is regenerating the para aminophenol, preventing exhaustion of the developer.

    I also think that the ascorbate is probably not operating directly as a developer. From what I have been able to learn by my limited reading, if ascorbate is operating directly as a developer one would expect some fog, but in this case there is essentially no fog. In fact, base plus fog on an unexposed piece of film was something like 0.04 density units. (Yes, I have the decimal point in the right place.) This would argue against direct developer action by the ascorbate.

    I eventually hope to follow up with more controlled experiments, but I thought I would mention the results of my preliminary experiments.

    Any thoughts on this?

  4. #74
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    IIRC there is a hint or two at this phenomenon earlier in this thread. I'm too lazy to look it up. The pH of borax is lower than that at which ascorbic acid will act as a developer, but it is still quite an antioxidant. As such, it regenerates most of the developers we consider as primary such as Metol, Phenidone and p-aminophenol. In the process, it causes the pH to be reduced, but given enough borax, the pH may not change enough to be noticable. Perhaps this action is not true superadditivity, but the combination of a small amount of p-aminophenol with a relatively large amount of ascorbic acid and enough borax to buffer out the changes of pH will be surprisingly active. One could start with 10 g sodium ascorbate and 1 g p-aminophenol in a liter and add borax enough to saturate the solution. It should do several rolls per liter. Phenidone is better because of its lower sensitivity to bromide.
    Gadget Gainer

  5. #75

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    Pat,

    Thanks for the comments. Reading the accounts of your experiments has been very influential in my thinking.

    Alan

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