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  1. #1
    chuck94022's Avatar
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    MacGyvering a tempering bath for color development

    There have been various discussions on how to control color chemical temperature during development, without resorting to a Jobo or some complex permanent bathroom plumbing.

    The most simple solution is to fill a tub or sink with water at a bit above the target temperature, immerse your chems, let the chems come up to temp, adjusting the water bath as needed until everything is just above 38 degrees C. If you are quick and efficient, you can get one process done before the temperature drops too much. But it is a bit stressful, timing is everything. This is how I started with my current darkroom (I used to have a Jobo years ago, but abandoned it after a home remodel).

    Some use a crock pot, rice cooker, or similar to preheat chems. This works, but accuracy may not be perfect.

    The ultimate home brew system would have a fully tempered water bath that is maintained within C-41 or E-6 specs. This can be done with a PID temperature controller, a heating element, and a water pump, inside some sort of water container large enough to hold chems and film processing tanks or drums. (I do light's out dip and dunk for my 4x5 sheet film, rather than tray developing. My water container is sized accordingly.)

    I have always wanted to build one of these systems, and just finished my first one. I have a plastic storage bin bought from the local home supply place. I found PID controller on the Chinese online shopping site (www.taobao.com) with temperature probe, already assembled into a little box with power switch, power cord, and switched power socket (controlled by the PID). The whole setup, including an immersable water heater, cost me less than $50 US Dollars (I bought it in China, where I'm living. That's the converted cost). With a system like this, you have to keep the water moving. I used a medium sized submersible aquarium pump, which cost about $10 USD, including a good length of tubing so that I could route the flow properly.

    Here are photos of the finished device:
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    It works like a champ, temperatures stay within .1 C very consistently in the bath. All for well less than $100 US. It took an evening to assemble.

  2. #2

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    nice job thank you for sharing, I built one too but PID you found is more convenient. Is it 220V unit? Do you know if 110V are available?

  3. #3
    chuck94022's Avatar
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    MacGyvering a tempering bath for color development

    Quote Originally Posted by wiedzmin View Post
    nice job thank you for sharing, I built one too but PID you found is more convenient. Is it 220V unit? Do you know if 110V are available?
    It is an SG-808G. It manual says it can handle 110, but I haven't tried it yet.

    It would probably only take an extra few hours to build one into a box like this.

  4. #4

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    Nice cludge chuck! Thanks for sharing.

  5. #5
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    I want to use an arduino with a SSR on an immersion heater to get something similar to this.
    Nicholai Nissen
    Kolding, Denmark
    nicholainissen@gmail.com

  6. #6
    chuck94022's Avatar
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    MacGyvering a tempering bath for color development

    Quote Originally Posted by nicholai View Post
    I want to use an arduino with a SSR on an immersion heater to get something similar to this.
    Go for it. But keep in mind that PID controllers are quite sophisticated in calculating how much heat to apply to a bath to regulate the temperature without fluctuation. It includes a self training function to tune the parameters to the bath.

    Given how cheap PIDs are, your project will certainly be done for love of hacking an arduino than for expediency. But have fun! You'll learn a lot I'm sure.

  7. #7

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    This is basically a DIY version of the Phototherm Model 14 tempering bath unit, which show up on Ebay from time to time. Sometimes as low as $50 but more often a bit more. Another option for the non-DIY types. I used a Model 14 for a long time when doing RA4 in drums, before moving to a Fujimoto CP31/51

  8. #8

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    I think this is as little of DIY as possible (make two holes in the container and seal it) and a very clean one. Good find by chuck94022.

  9. #9

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    chuck94022 do you know what kind of temperature sensor it is? K type, PT100?

  10. #10

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    Brilliant! Thank you for sharing!...since that's my bugaboo regarding color processing (it's a pain in the a** to get things to temp) a setup like this can make color almost as easy as B/W with greater consistency. I'm going to have to note this thread so when things calm down here I can look into doing this.

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