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  1. #1
    Eric Rose's Avatar
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    Barnbaum now uses the following dilutions for TriX 320 rated at asa 160.

    First he makes a stock solution of 1:3. Then he takes that and further cuts it to 1:12.5.

    If you were just going from the concentrate to the final dilution what would it be? Would it be 1:37.5? I just have a mental block when it comes to ratios and dilutions etc. Duh!!
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  2. #2
    jbj
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    first: 1:3 is equal to 1 part in 4 parts total, or 1/4 =25% v/v

    1:12.5 is equal to 1 part in 13.5 parts total, or 1/13.5= approx 7.4% v/v

    multiply 0.074 * 0.25 = 0.0185 or 1.85% v/v or approx 1.9% v/v

    then to see what the overall dilution factor is:

    solve the equation for x

    1/(x+1) = 0.019 x = 51.6

    so overall this is equivalent to approximately 1:51.6 dilution

    hope this helps,
    JBJ

  3. #3
    Eric Rose's Avatar
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    I stand in awe.

    As defined:

    A mixed emotion of reverence, respect, dread, and wonder inspired by authority, genius, great beauty, sublimity, or might.

    So if I want to make up 1000ml of working solution would I say 1:52 so that would be 53 parts in total. So 1000 / 53 = about 19ml. So 19ml of concentrate and the rest water to make up 1000ml?

    Geez this stuff drives me nuts!!
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  4. #4
    jbj
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    The main reason to do it in two successive dilutions is that it is (usually) more accurate to say dilute both 25 ml + 75 ml (1:3) and also 1:12.5 than to add simply add 18.5mL + 980.5 mL = 1:53 (999mL total)

    This is more accurate than what I posted the first time, remember I rounded up in my first post from 0.0185 to 0.019. So to be more accurate is a 1:53 dilution, or 1 part in 54 total (18.5 + 980.5).

    Another issue is the rate at which these solutions deteriorate. A concentrated stock solution will oxidize/deteriorate much slower than a dilute solution in which the pH is not as well buffered and more aeration has taken place (mixing fresh oxygen-rich water with concentrated developer).

    But to answer the original question:

    1:53 dilution is really close. That would be 18.5mL + 980.5 mL. 999mL total. I assume you have graduated cylinders that can measure an accurate half mL increment?

    good luck,

    JBJ

  5. #5
    Jorge Oliveira's Avatar
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    From a strictly practical view from someone tha have used HC-110 higly dilluted for a long time;

    If you use 19ml + 1liter water, it will be VERY much OK.

    I've never been able to tell the difference between 5ml concentrate to 295 or 300 ml water.

    Jorge O

  6. #6
    ann
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    Darn! I still confused and I mix from scratch all the time. Surely I am not the only one who is still lost? (And I am not even using that combination)

  7. #7
    Ole
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    Funny, these rounding-off errors...

    1:3 gives 1/4 concentrate. So the next step is: 1/4 : 12.5, multiply both sides by 4 to get 1:50.

    Why make it more complicated than it is?
    -- Ole Tjugen, Luddite Elitist
    Norway

  8. #8
    jbj
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    As Jorge pointed out, for practical use it probably doesnt matter that much for this particular developer/film combination. I don't use HC-110 so I cannot comment on that.

    However I do use D76 and TMX sheet and roll films. My experience with this combination, and what I have read from others, is that tight control over all aspects is important (temperature, agitation, concentration, time, age of developer, etc.)

    But, with respect, in strictly technical terms 1:3 further diluted 1:12.5 is not the same as 1:50

    (1/4) * (1/13.5) = 1/54 not 1/50

  9. #9
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    Beautiful Mind??
    Governing Dynamics?

    .... sorry -- I live near Hollywood
    My photos are always without all that distracting color ...

  10. #10
    Ole
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    Quote Originally Posted by jbj
    But, with respect, in strictly technical terms 1:3 further diluted 1:12.5 is not the same as 1:50

    (1/4) * (1/13.5) = 1/54 not 1/50
    It ends up as 1+50, not 1/50 concentration. The final ratio is 1/51... Which is what I dislike about the convention of writing 1:12.5 when what is really meant is 1 part A plus 12.5 parts B.
    -- Ole Tjugen, Luddite Elitist
    Norway

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