I made the biggest noob's mistake during mixing D76 powder !

Discussion in 'B&W: Film, Paper, Chemistry' started by edftwin, May 7, 2012.

  1. edftwin

    edftwin Member

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    Hi, i'm a total newbie to BnW developing.

    The very first and biggest mistake i made is when mixing the D76 powder to make up 3.8 litres developer.

    First, i prepared 3 litres of 50 C water and added the whole pack of D76, stirred till dissolved, BUT I added too much water in the last step !!
    I totally forgot the volume of powder that would increase the total volume after mixing into the 3 litre water, all thanks to the SLEEPY BRAIN !

    The volume of water i added in the last step was about 800 ML !! The stock developer has a volume of 4.6 LITRES !!

    The stock developer is no longer full strength, how do i calculate the ratio now?

    EDIT: I suddenly figured out the calculation...but i'm not sure if it's correct...

    The strength of the solution now is about 1:0.204 OR 4.9:1

    So whenever i develop let's say i wanna make 1+1, i'll have to use lesser water to dilute compared to the original chart in order to compensate...

    I need more advice ! Thanks !
     
    Last edited by a moderator: May 7, 2012
  2. Tony Egan

    Tony Egan Subscriber

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    It shouldn't make that much difference. Are you sure you have 4.6l or only added 800ml? Using 1+1 time charts you could adjust the dilution to 45:55% water to stock as one idea.
     
  3. edftwin

    edftwin Member

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    Hi, i re-measured the total volume, it is 5.1 L.
    1.3 L of water in excess.

    So the ratio should be...

    1:0.342

    I use 10oz/300ml steel tank,

    1+1 should be...

    Volume of developer needed: 201.3ml
    Volume of water needed:98.7ml

    correct?
     
  4. polyglot

    polyglot Member

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    If your total is 5.1L, your concentration is 3.8/5.1=0.75. That means that (for example), 100mL has as much developer in it as 75mL of stock. If you then added another 50mL water, you have 75mL of D76 in 150mL, or the 1:1 you're looking for.

    So in short, you mix at 2+1 to get the same dilution as 1+1. Your calculations are correct but you don't need to go to the 15th decimal place.

    I'm puzzled as to how you got an extra 1.3L in there though; I'm pretty sure that's more than you'd get if you just dumped the powder into 3.8L of water.

    Be comforted that this is a *cheap* mistake and you've probably ruined no images with it. The D76 will probably oxidize slightly faster (more water means more oxygen in solution) but I'm sure you'll still get 6mo+ if you store it carefully - read the FAQ in my signature.
     
  5. edftwin

    edftwin Member

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    First time mixing my own developer...just got over excited i guess...plus didn't sleep well for the past few days...:sick:
     
  6. paul_c5x4

    paul_c5x4 Subscriber

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    Don't worry, we all make mistakes.... Mine only last weekend was to measure out 2ml of 510-Pyro and add it to 300ml of water when I wanted a 1+200 dilution. Suffice to say, my negs came out a tad over developed.

    Fortunately, I had doubled up on my exposures, so the duplicate sheets went in to a D76 bath.
     
  7. Bill Burk

    Bill Burk Subscriber

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    The advice so far sounds good, I'm sure the D-76 is usable. But I don't know exactly what to expect... since the concentration of your stock solution is not standard, I would say don't plan on keeping this batch six months.

    Bill

    p.s. I work for Kodak but the opinions and positions I take are my own and not necessarily those of EKC (in other words, this is off the top of my head, I didn't go to Kodak engineers or library to get an official opinion on this)
     
  8. edftwin

    edftwin Member

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    Hi, i followed the calculations and developed a roll of tri-x...it's drying up now...can't wait to see the result !

    [​IMG]
     
  9. edftwin

    edftwin Member

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    Hi, i had a roll of tri-x developed last night, guess the calculations worked...the result seemed pretty well to my newbie eyes...