Impact of T° in the dilution of D76 powder ?

Discussion in 'B&W: Film, Paper, Chemistry' started by Rom, Sep 7, 2011.

  1. Rom

    Rom Member

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    Dear all,

    Does the T° has a big impact if not well controll when i prepare my D76.

    I do not have a thermometer which goes higher than 40° (yeah, you know which thermometer i have :wink: ).

    Kodak said that water has to be between 50 & 55°C, what happens if higher ?

    Thanks

    Rom
     
  2. I'm a relative newbie with home developing, but in the 2 batches of D76 I've prepared, I just set the tap to what seemed moderately hot and went for it. I've been pretty happy with the results I get developing several different kind sof b&w film. So my best guess is that the recommended temps are not critical values.
     
  3. espadrew

    espadrew Member

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    Temperature when Mixing

    For powders such as D-76 the higher temperature facilitates mixing but is not critical. Just get it as hot as you can. As a rough guide 50 degree C water is very hot to the touch. You can keep your hand in it but not for long.
     
  4. Rom

    Rom Member

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    Thanks all,

    Indeed I have warmed it till my finger feels quite hot.

    Will developp two rolls tomorrow.

    Thanks for your reply

    Cheers
     
  5. Rick A

    Rick A Subscriber

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    The only thing that matters when mixing D-76 powder is that it all dissolves. I mix contents of pack to 3/4 gallon very hot water. My water heater is set to 135f so I just run straight hot from the tap. When it's all dissolved I add cold from the tap to make one gallon. If you are using distilled water, decant 1/4 of it off and heat 3/4 g in the micro to around 125-130f and mix, pour in the balance of the water when finished. You can use as soon as it's cooled enough, make sure there is no entrained air in the mixture.
     
  6. MattKing

    MattKing Subscriber

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    Query - out of interest only:

    Can you damage your D-76 by using water to mix it that is at too high a temperature?
     
  7. Rick A

    Rick A Subscriber

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    Good question Matt, you can try mixing some in boiling water and post the results for us.
     
  8. MattKing

    MattKing Subscriber

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    Actually Rick, I can't - don't have any at hand, and I have enough liquid developers to tide me over for a while. But I was thinking about an XTol experiment ....
     
  9. michael_r

    michael_r Subscriber

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    It's an interesting question I've wondered about regarding virtually any powder developer. I have always tried to stay in the mixing temp range recommended by the manufacturer. My naive assumption was that while hotter water makes it easier to dissolve some chemicals, if the temperature is too hot perhaps there could be some kind of accelerated or runaway oxidation taking place during mixing, particularly with certain agents like Pyro, Phenidone etc that oxidize quickly to begin with. I might be totally wrong though.
     
  10. Rich Ullsmith

    Rich Ullsmith Subscriber

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    Chem 101 was a long time ago, but I think cold water can hold more dissolved oxygen than warm or hot water. Stirring the powder to dissolve also stirs in oxygen through turbulence, but if this process is shortened by using warm or hot water, less stirring and less turbulence.