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  1. #71

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    Quote Originally Posted by AndreasT View Post
    I would like to take up mixing my own chemicals. What I would like to to know is it correct or false to say that if I dissolve the accelerator in a seperate bath and mix the developer shortly before use that the developer has a longer shelf life.
    There are several factors that cause developers to go bad. The primary cause is exposure to oxygen. When stored in a filled glass bottle the pH of the developer has little effect on the storage life. Some developers may not mix correctly if the accerlorator is omitted to be added later. So to answer your question mix any developer as the formula specifies and do not make changes.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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  2. #72

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    Quote Originally Posted by AndreasT View Post
    I would like to take up mixing my own chemicals. What I would like to to know is it correct or false to say that if I dissolve the accelerator in a seperate bath and mix the developer shortly before use that the developer has a longer shelf life.
    I think this is true in some cases. For example, Diafine is long-lasting. You could mix two bottles similar to Diafine. Instead of using them as a two-bath, mix them together when you want to develop (and use it one-shot). Does anyone know of a two-part developer like this?

    Mark Overton

  3. #73

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    Most staining formulas would be examples of this. The alkali is always a separate concentrate. So I would say pH does matter if the developing agent becomes particularly unstable at the working pH and the amount of preservative is low. This is typical of staining and high acutance formulas that rely on relatively low concentrations of developing agent and sulfite at relatively high working pH values.
    Last edited by Michael R 1974; 01-13-2013 at 08:07 PM. Click to view previous post history.

  4. #74

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    In support of my previous statement, pyrogallol plus sodium hydroxide is used routinely in the sciences to scavenge oxygen from closed systems. If there is very little oxygen present there is little color change indicating decomposition. So in the absence of oxygen even this very unstable mixture is stable. I have vials of Neofin Blue that are decades old. They are still colorless since no oxygen can get in. Yet break the seal and the developer is quickly spoiled. So the danger to developers is not their alkalinity but exposure to oxygen. For most developers, which I assume the poster is talking about, leaving the alkali out makes little difference. As Michael pointed out certain special developers are an exception unless one does something similar to what Tetenal does.
    Last edited by Gerald C Koch; 01-13-2013 at 10:53 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #75

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    Quite true. What I should have clarified in my post was that in the end even for the developers I listed it is still oxidation at work rather than pH per se.

  6. #76
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    Quote Originally Posted by Philippe-Georges View Post
    I mix from scratch:
    Pyro-HD King formula, because it is hard to find in Europe (perhaps in Vienna at Lotus) but absolutely not in Belgium.
    E-72 (= Hydrochinon free Dektol) because it does not exist commercially.
    Buffered stop bath because it does not exist commercially in Europe.

    And, last but not least, I like doing it!

    What is Lotus in Vienna? Do they have a website?

  7. #77
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    What makes me wonder about seperating the developer is that I read somewhere D-76H doea not last long, somewhere else I read it does last long?? The Willi Beutler formula has the carbonate seperate for example. I was just wondering on the line of usually it shouldn't be a bad thing.
    Sure the developer should be in a closed bottle etc etc but then again...just wondering.

  8. #78
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    andreas,
    what is the question?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #79
    AndreasT's Avatar
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    The question is if I mix a developer and seperate the alkali/accelerater from the rest will its shelf life increase. Mixing the solution shortly before use.

  10. #80

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    Andreas - re-read Gerald Koch's answer above.

    We should also clarify what you mean by D-76H. Typically D-76H refers to the "Haist" version which omits the Hydroquinone and increases the Metol to 2.5g/liter. But there is also D-76h which is a buffered version of D-76.

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