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  1. #1

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    Heating Developing Solutions

    What are creative ways to maintain higher temperatures of developing solutions, for example, potassium oxalate? I want to maintain the temperature at about 110 deg F. (Or higher?) I'd like to have a device that's self-correcting with a sensor. Not just a heater.

    I tried a fish tank warmer, but that only goes to 90 degrees. I don't want to use a crock pot or coffee pot; these aren't self-correcting. It would be too hard to maintain a consistent temperature for repeatable results.

    The most creative idea I've heard from the Photo Formulary is using a waterbed warmer. These go to 100 deg, have a thermocouple sensor, etc. I'm checking to see if I can find one that goes to higher temperatures.

  2. #2
    Baxter Bradford's Avatar
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    I just had to buy a heater for water to go to 38 deg C from Nova Darkroom in UK. In finding out the temp I needed so they could recalibrate the temperature controller, it turned out that the stainless one I was buying was usually used for heating milk in an animal weening unit. It works absolutely fine with stable temps. The product wasn't listed in their Photographic catalogue, it came to light when making my telephone enquiry.

    You might like to pursue this line of enquiry in whichever country you live in if the photographic community cannot provide what you require.

  3. #3

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    I don't know if my fish heater goes to 110F or not. It certainly goes to 100F. Offically it only goes to 92F IIRC but the thing is adjustable. It's adjustable so you can make sure the thermostat is accurate. Of course some of us adjust it so it runs hotter then the label-)

  4. #4
    Joe Lipka's Avatar
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    I start with a styrofoam cooler, add microwaved hot water and drop in an aquarium heater. Into that, I put my plastic pitcher of developer with a thermometer. The heater does help retard the eventual cooling, so after an hour or two, I do have to reheat the water. A little more work to maintain temperature, but the advantage is an incredibly low cost of ownership. I really don't think that the temperature control is a major issue in Pt/Pd processing. I try to keep the developer between 96 -102 degress F.
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  5. #5

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    The simplest way IMHO is to just place the potassium oxalate in a small ice chest and fill the chest with water about 10 degrees higher than the desired temperature to compensate for initial lower developer temperature. Change or renew the water every thirty minutes or so during your developing session and there you have it. You could also keep the water warm with an aquarium heater, but many of these heateers can not be adjusted for temperatures of 110F since this is rathr high for most fish.

    Sandy

    Quote Originally Posted by Neil Poulsen
    What are creative ways to maintain higher temperatures of developing solutions, for example, potassium oxalate? I want to maintain the temperature at about 110 deg F. (Or higher?) I'd like to have a device that's self-correcting with a sensor. Not just a heater.

    I tried a fish tank warmer, but that only goes to 90 degrees. I don't want to use a crock pot or coffee pot; these aren't self-correcting. It would be too hard to maintain a consistent temperature for repeatable results.

    The most creative idea I've heard from the Photo Formulary is using a waterbed warmer. These go to 100 deg, have a thermocouple sensor, etc. I'm checking to see if I can find one that goes to higher temperatures.

  6. #6

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    Neil - how about getting a second hand "stirring hot plate"? These will not have a temperature feedback from the bath that you are wanting, but they are adjustable over a large range of temps - from luke warm to way over boiling. (I've accidentally melted aluminum foil on one once...)

    With the stirring hot plate, I would set up a water bath to put your solution in, i.e. a larger beaker for the bath water and a smaller beaker for your chemical solution. Make sure there is space between the beakers for water to circulate by suspending the inner beaker so that you can drop a magnetic stir bar in to get even better circulation of the water bath.

    Once you set this up and make adjsutments to the temp setting on the hot plate, you should be easily ably to get your solutions into the temp range you want and be able to hold the temp there for a long time.

    Kirk

  7. #7
    scootermm's Avatar
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    neil I bought one of these:
    http://www.free-recipes.co.uk/kitche...te-AHP303.html
    and an extra 1L/1qt Pyrex to warm it in. seems to work pretty consistantly. Ive figured out what the temperature knob turn is to keep it at 95degrees. so I start it up and put the pyrex with the Pot Oxalate on it and let it get at 95degree and leave it there between dev stages between prints.

  8. #8

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    Like Kirk says I use a stirring/hit plate to keep my solution warm. There is no need for the water bath if you use a thick enough container. I use a corning jug and heat 1 liter of PO to 120 ºF in about the same time it takes to make a print. I put the solution to heat at the same time I start the exposing unit and by the time I am done I have a warm solution.

  9. #9

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    Thanks for the ideas.

    I'm hoping to contrive something that's self-sustaining, that has a temperature sensor. Baxter's idea sounds like a possibility, because the current Nova Darkroom heating devices actually go to 44 deg. C or 45 deg. C on another. That's about 111 deg F, or a little higher. Only issue is that they run off of 220 volts. But, it shouldn't be that difficult to find a step-up transformer for 300 watts.

  10. #10

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    The stirrer also sounds intriguing for something that I might not do that often or am experimenting. This is one of the luxuries I afforded myself, when I built my darkroom. For mixing dektol and other powered chemistries. Works great; I just walk away and let it do its thing.

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