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  1. #1
    Ian Grant's Avatar
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    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
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    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #11
    gainer's Avatar
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    Meanwhile, back at the Gainer Dungeon, I may have jumped the gun when I said my attempt at Metolal was already showing signs of age. I think I didn't let it age to stability. I just tried it again at 1+50, 65 F, 10 minutes, 35 mm EDU 400 Ultra, and got this result, a scan of a print on RC VC paper.
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    Gadget Gainer

  3. #12

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    Quote Originally Posted by gainer View Post
    Meanwhile, back at the Gainer Dungeon
    Pat - I'm pleased you've taken to the world of pdfs so quickly, but I think you might find you can post photos as jpgs that look better than photos as pdfs.

    If you have any combiniation of two of the following:

    text, layout, and photos,

    then pdfs are probably your best choice. But the pdf generator will probably recrunch/compress the photo when it makes it into a pdf. If you stick with jpgs, they should post with the compression settings as you saved them.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  4. #13

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    Quote Originally Posted by Ian Grant View Post
    it's the developer that exhausts and need relplenishing, the dev can have no bromide.
    I think Alan on track with this.

    Bromide (and iodide) will be released as the films develop. That bromide will have an affect on further development. By adding bromide to the developer, it will minimize/supress the effect of the released bromide. It will slow the rate of the development reaction as there will already be an excess of reaction products present in the solution.

    Developer exhausts as well. And that will slow the reaction as well as have effects.

    I've pointed out in other threads occasionally, I think it is the use of hydroxide that makes Rodinal such a popular choice for stand development. Using hydroxide as the only source of pH gives an interesting set up that most film developers do not have.

    Hydroxide has no buffering power. When it is neutralized by acid, it simply turns to water, which does not buffer the pH. You don't get that with carbonate - when it buffers, you get bicarbonate, which can combine with excess carbonate present and form a pH buffer. Borax and Kodalk will buffer with the addition of acid as well.

    As the hydroxide is used up in the reaction, the pH being unbuffered, will drop rather quickly. So even though the pH of Rodinal is nearly pH 14 in the stock, and about pH 11.5 when diluted 1+100, it will probably be at a much lower pH at the microscopic level in the film.

    I'm sure PE can speak to the actual micro pH levels that can be measured in emulsions with the right kind of micropH probes.

    At least that's my understanding.
    Last edited by Kirk Keyes; 08-29-2009 at 05:35 PM. Click to view previous post history.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  5. #14
    Photo Engineer's Avatar
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    Alan;

    You are correct, and it is no theory. It is an established fact. In addition, Iodide is much more powerful than bromide and newer emulsions are more iodide rich on the surface.

    Ian;

    But then Rodinal concentrate containes bromide, right? Or do I misunderstand your answer #10?

    PE

  6. #15
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    Quote Originally Posted by gainer View Post
    Meanwhile, back at the Gainer Dungeon, I may have jumped the gun when I said my attempt at Metolal was already showing signs of age. I think I didn't let it age to stability. I just tried it again at 1+50, 65 F, 10 minutes, 35 mm EDU 400 Ultra, and got this result, a scan of a print on RC VC paper.
    Patrick;

    I thought you had added more Metol to the concentrate to estimate how much was oxidized. If so, which concentrate did you use? Was it the original or the "enriched" and younger version?

    PE

  7. #16
    gainer's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Patrick;

    I thought you had added more Metol to the concentrate to estimate how much was oxidized. If so, which concentrate did you use? Was it the original or the "enriched" and younger version?

    PE
    No, I added some ascorbic acid to this batch. I have several batches going now, but this is the oldest. The problem is that it's going to take a year to determine keeping qualities if it's any good. Much less, of course, if it's not. I'm hoping that a time history of some number of tests from the same batch will show a trend before a year.

    It was another poster who added Metol to his 1/3 bottle of old Metolal. I'm still learning. It seems I can get very good results at pH=11 or less in the working solution, but I don't trust either my pH meter or my ability to use it. It does read close to 14 in a stiff solution of KOH.
    Gadget Gainer

  8. #17

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    Pat - have you thought about trying an "accellerated" aging test? Perhaps you could store some of your aging test solutions out in the barn under the chick coop heater or in the egg incubator so they get stored at about 120F or so. You could probably see how they would age in a years worth of time in only acouple of months.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  9. #18
    Ian Grant's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Ian;

    But then Rodinal concentrate containes bromide, right? Or do I misunderstand your answer #10?

    PE
    Yes both Modern Agfa/A&O Rodinal and Calbe R09 contain Bromide.

    I was really answering Alan's point and meaning that other high acutance developers don't include bromide. But in fact some include small traces of Potassium Iodide. As Kirk points out it's the Bromide & Iodide in the emulsion itself that's plays the greater part.

    Rodinal works exceptionally well with modern films with a high iodide content like Tmax & Delta 100, so it's possible that a small addition of KI to a Rodinal substitute would help with some older type emulsions, but we'd only be talking somewhere in the region of 0.25g per litre of concentrate

    Ian
    Last edited by Ian Grant; 08-29-2009 at 11:55 PM. Click to view previous post history. Reason: add

  10. #19
    gainer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Pat - I'm pleased you've taken to the world of pdfs so quickly, but I think you might find you can post photos as jpgs that look better than photos as pdfs.

    If you have any combiniation of two of the following:

    text, layout, and photos,

    then pdfs are probably your best choice. But the pdf generator will probably recrunch/compress the photo when it makes it into a pdf. If you stick with jpgs, they should post with the compression settings as you saved them.
    I looked at both formats, and can send either one. According to the rules for allowable file size, I must cut the .jpg file to a smaller transmitted size than the .pdf. My internet is by dial-up with a maximum rate of 26.4 k because I live in the boonies and can't afford to use the satellite. We are supposed to get fiber optic telephone lines here, which will allow me to get DSL. I hope I live to see the day.

    I am not so much concerned about grain or sharpness at this stage. When I get to that point, I will send a lower resolution overall and a high resolution of a portion. I will be more careful in setting the exposure next time. I bracket, but if, as in this case, I don't expose for the shadows, some information will be lost.

    So far, I am pleased with the grain, gradations and sharpness of this developer. There is, of course, practically no sulfite in the working solution, even if the good K2SO3 is used.

    I'm going to try using potassium ascorbate in place of the sulfite in a small batch. When I tried it before, it was not so good, partly because it was before I got the idea of using the p-aminophenol base. (I did not know the history of Rodinal as has been exposed here, and thought the formula in "The Darkroom Cookbook" was IT.)
    Gadget Gainer

  11. #20
    gainer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Pat - have you thought about trying an "accellerated" aging test? Perhaps you could store some of your aging test solutions out in the barn under the chick coop heater or in the egg incubator so they get stored at about 120F or so. You could probably see how they would age in a years worth of time in only acouple of months.
    Don't have a barn. Three horses, 3 goats and a gaggle of chickens. There is a henhouse, but the chickens are their own incubators. We have a bountiful sufficiency of large eggs.

    I have a brisker oven that keeps about 104 F that I use to keep some solutions in glycerine fluid enough to measure. I'll but a batch in there and see how it does when I remember where I put it.
    Gadget Gainer

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