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  1. #21
    Photo Engineer's Avatar
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    Quote Originally Posted by tiberiustibz View Post
    The problem with those plates would be the residual heat kept up in the plate. If you turn it on 10 and then shut it off when the bath reaches temperature, the bath temperature will continue to rise for some time after.
    That is why the ones without the controller require constant attention. With the controller, this does not happen.

    OTOH, if you use a large water bath on the hotplate, the overshoot is minimized due to the inertia of the water and a glass container (pyrex) minimizes this to an even greater extent. Use of Stainless or other metal containers tends to maximize losses and cause bigger over and under shoot.

    PE

  2. #22
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    Quote Originally Posted by Photo Engineer View Post
    OTOH, if you use a large water bath on the hotplate, the overshoot is minimized due to the inertia of the water and a glass container (pyrex) minimizes this to an even greater extent.
    The idea of using a large bath for it's inertia and buffering the heat transmission with glass fits nicely into what I am trying to accomplish; reasonable manual control.

    One of my concerns is the physical size of what I want to keep hot, specifically I would like to be able to keep "all the chemicals" at the same temp. For C-41 that means 4 one-liter measuring jugs and a developing tank or two. For RA-4 that may mean a 16x20 tray.

    Yes I do now understand that room temp works fine for RA-4 but my darkroom temp can vary from say 60f in winter to 85f or so in summer. I really need to have some heat source in winter anyway so standardizing at about 92 as recommended in tech pub J39 seems prudent. That also shortens the time in the tray which is also preferable.

    I did find an infinitely adjustable hot plate that may work. Given it's limited diameter I can see that I would need to build a support of some type to keep a good size water bath upright and I may actually want to use two of these.

    I also found this double burner consumer model and one or two others that seem cheap enough to try and these would appear to provide a more stable base for a large turkey pan or similar dish.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  3. #23
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    Mark;

    How about a fish tank heater and a pump. Fill a tank with water, bring it to the right temp and then place your bottles in it with solutions to temper. This would work. Also a beaker on a hot plate with a fish tank pump to circulate into a larger tank with the chemicals in them.

    Just be careful. A lot of pyrex containers that work well in ovens or microwaves will NOT work on hotplates or the dual units you have referenced above. You can tell which will not work by the statement (NOT FOR STOVE TOP USE OR HOTPLATE USE).

    PE

  4. #24
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    heating pads

    Quote Originally Posted by markbarendt View Post
    Anybody tried using a hot plate as a heat source for keeping color chemicals at the right temperature?

    I'm using small tanks for film and trays for prints.
    (snip)
    Mark,

    Take a look at the horticultural type warming pads.... low enough wattage... (and an available thermostat you can purchase) that should allow for reasonable temperature maintenance.

    <http://www.americanhort.com/root.html#Anchor--Pr-7027>

    The thermostats (which one should expect to be 'waterproof' in a horticultural environment) are further down that page...

    Ken
    Quando omni flunkus moritati (R. Green)

  5. #25
    markbarendt's Avatar
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    Quote Originally Posted by Photo Engineer View Post
    Mark;

    How about a fish tank heater and a pump. Fill a tank with water, bring it to the right temp and then place your bottles in it with solutions to temper. This would work. Also a beaker on a hot plate with a fish tank pump to circulate into a larger tank with the chemicals in them.

    Just be careful. A lot of pyrex containers that work well in ovens or microwaves will NOT work on hotplates or the dual units you have referenced above. You can tell which will not work by the statement (NOT FOR STOVE TOP USE OR HOTPLATE USE).

    PE
    Thanks PE. I may stick with a metal pan and plastic measuring jugs to start.

    I have tried a modified fish tank heater in the bath along with a hot pad underneath it, they both seem to be made for lower temps and just don't have the oomph needed to keep up with a good size tray at 100; low 90's are workable. This is actually the way I warm my secondary C-41 chems, and RA-4 and LPD developers now.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  6. #26
    markbarendt's Avatar
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    Quote Originally Posted by KenS View Post
    Mark,

    Take a look at the horticultural type warming pads.... low enough wattage... (and an available thermostat you can purchase) that should allow for reasonable temperature maintenance.

    <http://www.americanhort.com/root.html#Anchor--Pr-7027>

    The thermostats (which one should expect to be 'waterproof' in a horticultural environment) are further down that page...

    Ken
    Those look interesting, 200 watts seems a bit low for my application though.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

  7. #27

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    [QUOTE=markbarendt;973921]Anybody tried using a hot plate as a heat source for keeping color chemicals at the right temperature?

    Was recently given the heating mat from a water bed. It's about 40" long and 10" wide with a thermostat about 20" long. Have tried it to see if it works and it does. Only thing now is to tune the thermostat.

  8. #28
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    Well I picked up a 2-burner GE hot plate at WalMart for $33.

    It is sweet!

    Looks like it holds within a degree or so if I leave things alone. The thermostats adjust infinitely and cover all the temps I'll need.

    Close enough for this boy.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Ana´s Nin

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