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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.
    __________________
    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. #161

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    Quote Originally Posted by gainer View Post
    I seem to remember seeing an acorbate form of Metol, using, I guess. ascorbic acid in place of sulfuric acid on its tail.
    Pat - what about trying an Amidol analogue of Rodinal? Then you just have to deal with a chloride which should be much more soluble than a sulfate. Or what about a Glycin analogue - you don't have to worry about any salts then. You stil lhave the para-aminophenol backbone structure as in Metol and the para-aminophenol.
    Kirk

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

  3. #162
    Ian Grant's Avatar
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    The problem is Amidol doesn't keep well in solution, nor does Glycin. Ilford worked on a Phenidone - Glcin concentrated developer but in commercial production it had poor shelf life.

    Meritol the combination of PPD - Pyrocatechin has been used and had a better shelf life

    Ian

  4. #163
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    I'm about to give up on a Metol analog of Rodinal. I could more easily concoct a Metol-C-TEA. I have a compound of Metol and C in glycerin. I call it a compound becuse it seems to be more than a solution. It has 2.5 grams of Metol and 4 grams of ascorbic acid in 100 ml, and took 250 F to get it there. Now I'm out of Metol, but have more p-aminophenol coming tomorrow. I don't like the idea of using KOH, mostly because it's hard to tell what I'm getting when I weigh it because it turns into a puddle while I weigh it. I probably should have made a solution as soon as I opened the container, or else sprung for the money to get it in the solution form. I'm going to see what happens when I use K2CO3 to form the potassium aminophenolate. The CO2 should fizz away for the most part with a little help from heating. We'll see. If that doesn't work, I'll see what I can do with K2CO3 and Ca(OH)2, which will at least make a solution of KOH and a limestone rock I can use as an ornament.
    Gadget Gainer

  5. #164
    Trask's Avatar
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    Ian -- I was under the impression that glycin didn't keep well in powder form (note Photographers' Formulary's comment on glycin that it has a limited shelf life), but that when it was in solution it would remain stable and active for quite a while, even if it did darken.

  6. #165
    Ian Grant's Avatar
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    Glycin caused keeping problems for both Ilford & Paterson developers, but you could use it where shelf life isless important. The importance of Rpdinal is the very long shelf life etc.

    Ian

  7. #166
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    Glycin keeps well in solution, but keeping worsens as pH goes up. It is quite stable in a 2 part developer. Amidol keeps poorly in solution at any pH unless one adds certain stabilzing agents.

    PE

  8. #167

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    Quote Originally Posted by gainer View Post
    I don't like the idea of using KOH, mostly because it's hard to tell what I'm getting when I weigh it because it turns into a puddle while I weigh it.
    You can titrate it with a standard acid. You can make a standard acid by titrating that with a standardized base. Or, you can use potassium acid phthalate (KHP, or potassium hudrogen phthalate) which is a common standard acid and titrate the KOH solution directly with the KHP solid. Use phenolphthalein as the indicator.

    That's what all the hip lab cats do, man.
    Kirk

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

  9. #168

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    Quote Originally Posted by Ian Grant View Post
    The importance of Rpdinal is the very long shelf life etc.
    I thought it was the result of the development that was important...
    Kirk

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

  10. #169

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    Tetenal seem to know how to make metol based developer of high pH that keeps well, see the msds for Neofin Blue in the thread on High Acutance Developer.But they are not likely to spill the beans on how it works.

  11. #170
    Ian Grant's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    I thought it was the result of the development that was important...
    Of course

    It's the simplicity of Rodinal combined with the quality of the negatives produced that lead people like Patrick in search of similar developers using different developing agents.

    But in a 100+ years it's been copied by many other companies, including Ilford & Kodak but no-one has yet come up with a simple alternative using other developing agents, that keeps well as a single solution concentrate.

    This is why Rodinal is so remarkable.

    Ian



 

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