The temperatures in my house fluctuate wildly. I spend a fair amount of time before printing just bringing my chemistry to temperature. Are there any automated solutions or aids that help with this? I'm imagining an incubator rack where I can insert 4 1-liter bottles of solution and come back an hour later to find them all at 68F.

  • We're talking about chemicals for printing, not film developing, right? For printing, temperature isn't very crucial since paper develops more or less to completion in a few minutes time. For cooler temperatures, you should be able to add time and achieve the same result. Is your aim to avoid having to do this? Temperatures of the other baths should matter less. – bvy Apr 23 '17 at 15:07
  • @bvy This is for printing, yes. I've been focused on learning to develop negatives for a while, so maybe I'm over-focused on temps for printing. I am someone who works best with fewer variables though, so working with the same temperature all the time will help me achieve more consistent results. – steel Apr 23 '17 at 18:40

I've been looking at this today and the new solution seems to be a suitable vessel (one of those plastic stacking storage bottles would probably be ideal) and a sous vide wand - lots of photographers are reporting that they are simple, fast and highly accurate in maintaining temperatures.


I just googled for 68 F hot box to see what came up and I was surprised to see that home brewing may also be your friend here.

From the first random link I saw 9 Devices That Can Heat or Cool Your Fermenter

When it comes to fermenting, temperature is one of the most important steps towards happy yeast.

Ale yeast is happiest at 68 to 72°F, while lagers usually perform best at 45 to 55°F.

I followed a link to Amazon from that article and found: Inkbird Pre-Wired Dual Stage Digital Temperature Controller Outlet Thermostat 110V, 1000W Heating and Cooling for Fermentation Kegerator ect which costs $35. Which could be the basis of a home built system for you.

So while I don't have a specific solution, looking at other hobbies that require temperature regulation will open up a bunch of different potential solutions.


Adjusting and keeping the chemicals of the process is a challenge faced by every amateur darkroom enthusiast. Best is a water bath. Procure a plastic pan large enough to hold the bottles. It wouldn’t hurt if there is room for the developing tank. You place the chemical bottles in the pan filled with water. The water level should be deep enough to half submerse the bottles. Now add hot water or ice to this water bath. The idea is to bring the solutions in the bottles to temperature. Once the temperature of the fluids are adjusted and checked, you can start the developing sequence. Load the film onto the reel in total darkness and place the film in a lightproof developing tank. During the developing phase, you park the developing tank in the water bath; this keeps the fluid inside spot-on.

Throughout this darkroom regimen, you regularly check temperatures. You can simply add hot water or ice to the water bath. If you will be doing this on a regular basis you can get more elaborate. You can install a thermostatic mixing valve on your incoming darkroom water line. These are expensive but worth the money. You will need a darkroom that has a working sink. You run tempered water into a pan that contains the bottles. Also, chemical laboratories frequently use a water bath. You can purchase an inexpensive electric water bath tray; check the web or find a chemical supply house. This tray uses a submersed electric water heater with a thermostat. Luckily, most color processes call for elevated fluid temperatures. This is no accident; setting the processing temperatures high avoids the need to refrigerate the solutions.

If you need to adjust a fluid temperature quickly, use a plastic baggie filled with ice or hot water. You dunk this into the fluid, the baggie method keeps the temperature adjusting fluid contained so the chemicals are not diluted.

  • my question was about printing, actually. Maybe that wasn't as clear as it could be. Does your advice stay the same? – steel Apr 23 '17 at 18:42
  • The chemicals are brought to the desired temperature using a water bath. Trays that will hold the chemicals are on the bench empty. When ready to process, pour the chemicals into the designated trays and proceed. When the developing of this batch of prints is complete, return the fluids to their containers in the water bath. This is a batch process. Inexpensive water bath trays are available from most chemical supply houses -- look at Edmunds Scientific. – Alan Marcus Apr 23 '17 at 20:58

They are pretty standard items in most labs... The problem is that they usually cost a fortune. Many of them have a hose and pump that allow you to circulate the cooling fluid (in your case, water) through some other apparatus or larger container. E-bay has some here. If you're into do-it-yourself, I'd suggest looking at thermoelectric coolers such as this. It can heat or cool contents depending on the polarity of the 12V power source. A cheap temperature controller such as this coupled with an 'H' bridge controller such as this or this. Some learning will be involved.

This is probably overkill for your application. A mixing valve like this might be better for you if you have a source of hot and cold water available and are willing to do some plumbing.


Try Jobo Color Processor or Jobo Tempering Box. New they used to cost a fortune (and I am not sure they are made new anymore) but they occasionally come up on the well known auction site.

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  • Thanks, this is exactly what I was envisioning. Pretty dang pricey, you're right. – steel Apr 23 '17 at 19:08
  • These were mainly used in the professional color business, where every degree counts and the costs were borne by the client. B&W printing processes are more forgiving. Also check out the Nova Print Processor - theimagingwarehouse.com/ProductGrp/Nova-FB-Print-Processor - these slots come in cheaper unheated and more expensive heated versions. They are pricey too, but super extra fun to use - you keep your chemicals there for months to end (replenishing your developer of course) and just pop into your darkroom for a quick print or two. No hassle with filling up and emptying trays. – Jindra Lacko Apr 23 '17 at 19:18

For black and white applications, such a device might be overkill. Film and paper develop over a range of time/temperatures combinations (unlike color applications where time and temperature are crucial). It might be best to adapt your workflow to ambient temperature. But a water bath will bring your chemicals to temperature quickly. For long print sessions, you might consider a solution like floating trays in a large water bath (like a large sink) if your work area will accommodate it.


For my black and white processing I use a large washing up bowl half full with water. A 100w aquarium heater/thermostat and a separate imersive digital thermometer for accuracy. Our darkroom setup is in the garden and can be quite cold at times. 20mins standing in the heated 20C water keeps the chemicals just fine. I stand the film container in there too between agitations. Once done, the water is reused to mix chemicals for the print trays. Works a treat. All available via Amazon for £25.


One option is exploring thermostats for aquariums:


I can not recommend a specific model or brand, but it is an idea.

As all electric gear, disconnect it before putting your fingers inside the water.

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