Adding carbonate

Discussion in 'B&W: Film, Paper, Chemistry' started by Jarvman, Oct 20, 2010.

  1. Jarvman

    Jarvman Member

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    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. Jarvman

    Jarvman Member

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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. Photo Engineer

    Photo Engineer Subscriber

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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. Jarvman

    Jarvman Member

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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. Mike Wilde

    Mike Wilde Member

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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.
     
  6. Jarvman

    Jarvman Member

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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. piu58

    piu58 Member

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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.
     
  8. Gerald C Koch

    Gerald C Koch Member

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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.
     
  9. el wacho

    el wacho Member

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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. Jarvman

    Jarvman Member

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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.
     
  11. Removed Account2

    Removed Account2 Inactive

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    Are you 100% sure the chemicals are marked correctly? This doesn't sound TOO convincing : " 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 "

    Adding sodium carbonate to a weak developer most assuredly makes the developer more active.
    If it is a high Ph developer, like Rodinal concentrate which was formulated with NaOH, you'll be diluting the mix and get less activity.

    But in this instance I'm nearly 100% sure you or the previous owner mixed up the labels. can't find no reason for this.
     
  12. Jarvman

    Jarvman Member

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    Erik, if that was the case the other chemicals that I was given. i.e the metol and the hydroquinone I used to make parts A and B wouldn't have had the effects they had. They were bahaving exactly as they should (more part B giving more contrast). Which is why I think its very unlikely that the labels got mixed up. The sodium carbonate looks identical to the 2.5 kilos of it I bought new directly from silver print. Very fine, almost like flour when compared with sulfite that has grains more like sugar.
     
  13. fschifano

    fschifano Member

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    Hey, maybe the developer doesn't keep so well? Beers' developer isn't anything that special; it's just another MQ formulation not terribly unlike scores of other paper developer formulae. You bottled up a working solution developer and kept it over night. We don't know how many prints you ran through it before putting it away either. Adding carbonate to an already half dead developer isn't going to make it magically spring back to life.
     
  14. 2F/2F

    2F/2F Member

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    To my recollection, yes, it does say how to make the solutions he recommends having on hand (a bromide solution for lowering contrast and a carbonate solution for raising it).

    At any rate, a 10 percent solution means 1 gram of carbonate in 10 mL of solution. He also says what "percent solutions" are in the book.
     
    Last edited by a moderator: Oct 25, 2010
  15. Jarvman

    Jarvman Member

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    Cheers 2f, I'll have another look in there. Frank, I put very few prints through there and put 800ml in a litre bottle and used anti-oxidant spray to displace any oxygen in the bottle. The solution hadn't yellowed at all. Which is why I was confused. Wasn't expecting it to sprint back to life, was just expecting it to work more or less like the night before.