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  1. #1

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    Thermometer for Color Processing?

    Can anyone provide a suggestion on a good thermometer for use in color film development? I have been doing black and white for 30 years and just starting to explore doing my own E-6 at home. I know temperature control and accuracy is critical so I wanted to make sure I got a good thermometer.

    Thanks

  2. #2
    chriscrawfordphoto's Avatar
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    The Kodak Process Thermometer was the best. Accurate to 1/8 degree, but they're not made anymore, discontinued years ago because it was a mercury thermometer. Scientific supply companies still sell highly accurate mercury thermometers.
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    For several years when I was processing color reversal film I used an ordinary mercury lab thermometer. Never had any problem either with density or color balance.
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    Ken Nadvornick's Avatar
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    Quote Originally Posted by largeformat65 View Post
    Can anyone provide a suggestion on a good thermometer for use in color film development?
    Gerald mentions lab thermometers. Have a look at these affordable, general purpose, non-mercury lab therometers offered by ICL Calibration Laboratories, Inc. (Note that they are affordable because they are not formally calibrated and certified.)

    Ken
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    I used to use a dial thermometer, a metal one with a long metal probe part and a dial for reading temp. Then I discovered it was 2 or so degrees out of calibration and went to using plain old floating darkroom thermometers. They work great but they are slowwww. I keep one in my water bath (A standard scientific lab water bath) and stick a clean one in the chem bottle to verify temp just before processing.
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  6. #6

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    Search Ebay for a Kodak Process Thermometer Type3.. This one is very high priced but if you wait you can get one for under $30 like i did..

    http://www.ebay.com/itm/KODAK-DARKRO...item2a2381b74c

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    I use an old Jobo 3321 thermometer, accurate to 1/10th of a degree C, that I picked on ebay for 10 or 20 euros. It seems very accurate and I had no problems developing E6.

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    It's easy enough to calibrate a thermometer and save quite a few dollars. An ice-water mix is 0oC and once corrected for atmospheric pressure boiling water is 100oC. Various organic compounds can also be used. Certain compounds are better than others. The substance should be of reasonable purity and the molal freezing point depression constant must be small. A good choice would be naphthalene (one type of moth crystals) since it melts at 80.2oC and the constant is 6.9 oC/mole. The naphthalene would have to be very impure for the Mp to be significantly in error. Make sure to buy naphthalene and not paradichlorobenzene moth balls.

    Melt the naphthalene making sure that it comes up to the immersion line of the thermometer. Then record the temperature as a function of time. The temperature will first drop as the naphthalene is allowed to cool. Then the temperature will level off as it begins to solidfy. Finally the temperature will again begin to drop when all the naphthalene has solidified. Now graph your results. The temperature for the middle of the straight line portion of the graph represents the freezing point 80.2oC.

    When using melting/freezing points remember that both solid and liquid must be present for the result to be accurate.
    Last edited by Gerald C Koch; 10-09-2012 at 01:45 AM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

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    Absolute accuracy is not essential. What is essential is consistency. I am reasonably lucky to have a mercury thermometer which when bought was guaranteed to be accurate to within .25 of a degree. I also have a Kodak digital thermometer which didn't come with any guarantee of accuracy but when compared with the mercury one they read the same. I use the digital one in preference because it has a metal probe and responds to changes quicker than the glass mercury. It is also easier to use as well.

    What I am trying to say here is buy a good thermometer and compare it with a certified one and note any difference. On the other hand there are so many variables that I don't think +/- 1 degree makes a terrific load of difference so long as you have consistency.

  10. #10
    AgX
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    A very cheap, high accuracy way would be using a digital clinical thermometer. Though, as their fluid-stem counterparts, they have a maximum-value duisplay. Handling such could become annoying.

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