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  1. #1

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    Adding carbonate

    Ok, so I came across this in the darkroom cookbook. That adding carbonate to a developer will increase its activity and yield an apparent increase in contrast by deepening blacks. I've been playing about with beers developer a little last night and after trying 3 different mixtures settled on one. Last night I printed an image for 8 seconds at f/8. Bottled 800ml in a litre container, sprayed anti-oxidant spray in there, capped the bottle and left it until today. Today I tried to print the same image, the same size but adding 75ml of 10% sodium carbonate solution to this same 800ml of developer. What I thought would increase the developer's activity and deepen blacks has actually had the opposite effect. it's killed the blacks and it appears that closer to 16s at f/8 is what I'd now need to expose for. So an apparent decrease in activity. I was wondering whether someone could elaborate on what might be going on. Cheers, Gareth

  2. #2

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    Oh, i forget to add that I used some older sodium carbonate (anhydrous) I was given with a bunch of chemicals to make the 10% solution rather than the newer stuff that formulated the beers developer with (also anhydrous). Does this stuff go off at all? Or am I literally adding the wrong thing?

  3. #3
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    Gareth;

    Carbonate normally raises pH and the solution becomes more alkaline. IDK what is going on, but the usual effect is to raise contrast and Dmax when pH goes up.

    PE

  4. #4

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    Cheers PE. I've just tried using the slightly lower contrast mixture from last night which I haven't added extra carbonate too and it's behaving in much the same way. Lesser dmax and more exposure needed. Something else must be going on. Maybe its at a lower temperature. I'm certain the enlarger settings are all exactly the same though.

  5. #5
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    This might be a stupid question - but is there any voltage stabiliser on the enlarger power supply?
    If you exposed one lot late at night when electrical load is light, you could be getting a quite a bit higher voltage than you expect, and then the next day, if you expose during the daytime, the voltage drops due to other loads on the line could markedly (though not likely by two stops) cause changes in the light output.

    The other variable might be printing one with a MG filter in, and the other with it out?

    The other thing is your bulb might be about to burn out; they burn a fair bit brighter sometimes, then dim, then die.

    I can't find the reference at the moment, but I seem to recall that there is something like a 3% light output change per 1% voltage change.
    my real name, imagine that.

  6. #6

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    Hi Mike, I'm printing at the same time of day and have a voltage stabilizer. The bulb is fairly new I think.

  7. #7
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    A developer needs some kind of alkali. In this respect there exits developers with very weak alkali (sulfite only), weak alkali (borax), strong alkali (soda) and very strong alkali (caustic soda, rarely used). You can only "push" a developer with weak or very weak alkali by adding soda. If the solution contains already carbonate, the effect of more alkalify will be small. But you have a lot more of solved substance the, which reduces the activity of all other components. This is what you found.
    ---
    Uwe Pilz

  8. #8

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    When you look at the instructions for the Beers developers it appears that one could obtain all paper grades by merely changing the developer composition. This is not true and the range of contrast obtainable is rather small. If Beers really worked well there would be no need for graded or VC papers. The Beers developer is used more often for softer gradation than for contrast increase.

    It is my experience that people who complain of poor blacks are either not exposing the print correctly and/or pulling the print too soon and not allowing the blacks to reach their full depth. Try developing for 25% to 50% longer. A general purpose print developer such as D-72/Dektol will produce excellent blacks if used properly.
    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

  9. #9

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    hi,

    perhaps the oxygen in the developer solution itself has oxidized some of the metol? i guess a colour change ( i little yellowing ) would indicate so. i've experienced this with one day old dektol, kept in a bottle overnight. if you use the emergence time to calculate total print time you can compensate to a degree. hope this helps.

  10. #10

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    Interested what keeping a bottle '10% carbonate' handy means still. It doesn't specify in the darkroom cookbook what to use.

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