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  1. #1

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    I'm interested in a controlled, predictable method for lowering fluid to a target temperature. My situation is this: I have a very minimal B&W darkroom setup with no dedicated sink (other than the kitchen sink which does double duty for food preparation). I want all my film processing chemicals and wash water to be the same temperature.

    Currently, I fill several gallon jugs with water and allow them to sit overnight on the darkroom (a.k.a. converted walk-in closet) floor along with the bottles of fixer and developer concentrate. When I'm ready to develop film, all the chemicals are the same room-temperature. This works fine when room temp is less than 75 degrees, but my not-airconditioned apartment will soon be warmer than 75 degrees, and film processing times with Pyrocat-hd 1:1:100 get awefully short at > 75deg.

    So, I'd like to use my freezer to lower the temperature of my fixer and distilled water jugs to match the water that comes from the tap, which in my experience tends to be about 65 - 75deg during the summer months in my locality. What I am hoping for is a formula, spreadsheet, or table that allows me to plug in the volume of liquid, starting temperature, and the ambient temperature of my freezer with the result of the calculation being how long before the liquid reaches a target temperature.

    I've scoured Google and www.photo.net/search for any clues and haven't found what I'm looking for. Any tips or help would be appreciated!

    --Philip.

  2. #2
    Joe Lipka's Avatar
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    Ummm, that's way too high tech for me. Why not just put a few ice cubes in a ziploc bag and dunk in the chemicals. After a few tries you should be able to determine that X number of ice cubes will lower the temperature of a jug of developer to 70 F in Y minutes.

    Simple is good.
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  3. #3
    jovo's Avatar
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    as joe observed, what you are looking for seems to be rather high tech and involved. one of the more typical solutions is to fill a basin with water the same number of degrees cooler than the chemicals are warm, and let them sit until they are all uniform in temperature. the other circumstance of using hot water for too cold chems is very effective and quite quick. cooling them off will likely be slower, but just as effective.

  4. #4

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    hi philip -

    i had a darkroom in a factory building at one point where it was a sweatlodge in the summer months and barely above 'pipe bursting" temperature in the winter months. both joe's and jovo's methods were employed ... the only think i did which they did not mention was stir the chemicals a little bit to assure uniform temperature

    much easiser than stashing jugs of chemicals in a freezer

  5. #5

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    Hi phillip -

    Good advice from all who have posted.

    An additional reason not to use a freezer. Some of the chemicals may come out of solution.
    Tom Hoskinson
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  6. #6
    Bruce Osgood's Avatar
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    This is a simple formula I've been working with to reduce temp of stock to by adding cold water to make a working solution to be used immedieatly.


    X=((A/B)-(C/(B-D)))*-(B-D)

    A = DESIRED FINAL TEMP -- F
    B = TOTAL # PARTS OF BOTH SOLUTIONS
    C = EXISTING STOCK TEMPERATURE -- F
    D = # PARTS OF DILUTION WATER ONLY
    X = NEEDED TEMPERATURE OF DILUTING WATER ONLY

    To make an 8 oz 68 degree solution from 72 degree stock solution at 1 + 2 ratio would be:

    55=((A[68]/B[8])-(C[72]/(B[8]-D[6])))*-(B[8]-D[6])

    This works for me when tempering small amounts for processing rolls of 35mm. It may not be sophisticated, or beautifully written, but it works.

  7. #7

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    Quote Originally Posted by Bruce (Camclicker)
    This is a simple formula I've been working with to reduce temp of stock to by adding cold water to make a working solution to be used immedieatly.


    X=((A/B)-(C/(B-D)))*-(B-D)

    A = DESIRED FINAL TEMP -- F
    B = TOTAL # PARTS OF BOTH SOLUTIONS
    C = EXISTING STOCK TEMPERATURE -- F
    D = # PARTS OF DILUTION WATER ONLY
    X = NEEDED TEMPERATURE OF DILUTING WATER ONLY

    To make an 8 oz 68 degree solution from 72 degree stock solution at 1 + 2 ratio would be:

    55=((A[68]/B[8])-(C[72]/(B[8]-D[6])))*-(B[8]-D[6])

    This works for me when tempering small amounts for processing rolls of 35mm. It may not be sophisticated, or beautifully written, but it works.
    You forgot to factor in windage.

  8. #8

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    Bruce, I'd need a spreadsheet for that!

    I have the same problem in summer and use the diluting water to temper my developer. I make up a bucket of wash water at the required temp and place my pre-mixed bottle of fixer in a jug containing water from the fridge. While I'm agitating the developer, I agitate the fixer (shake the bottle a bit) and check it's temp. I usually have to remove it from the cold water bath before my development time is up as it's down to the desired temp.

  9. #9
    gainer's Avatar
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    My well water is never warmer than 65 F, so I make frequent use of the microwave to adjust temperature. I have on occasion put a 500 ml container of solution in the freezer if it was too warm. I think ice in a ziplock bag is the best suggestion so far, unless someone knows how to run a microave backward.

    There are in fact solid state cooling devices related to bimetalic strips that might be made submersible. These are used as coolers for electronic equipment.
    Gadget Gainer

  10. #10

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    Thanks to all who replied with ideas regarding my original post.

    --Philip.



 

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