Process Temperature Control

twelvetone12 · Apr 20, 2018

I've been experimenting temperature control without using my jobo processor (which is dead again). My idea is to basically imitate the tempering bath with a big jug of water that I keep at 38 degrees (as you can see from the photo).
I did some tests with E6 and I could not really keep the temperature of the chemicals stable at 38. When measured after pouring out from the tank, it was more between 36 and 36.5.

My process is like this:
* Bring all the chems to temp in a big tray
* Make my 5L jug at 38.3. I stir to make sure the water is not stratified and there are no hot/cold spots
* I keep a recipient full with very hot water, which I drop into the water bath if it drifts under 38°.
* I did the preheat with only water to make sure the tank was at 38

When I'm ready to pour the developer:
* I make a dedicated hot water bath and immerse the bottle. I continuously stir the developer to make sure it is 38.0 spot.
* When this temperature is stable, I pour it into the tank.
* Tank goes in the water bath (which I keep to 38.3) and I agitate following instructions.

When I poured out the chemistry for FB, CD and Blix it was always around 36! Is this the expected outcome? Can the temperature drop so quickly when pouring it out of the tank?
I thought my process was quite fail-proof but evidently is not... and I ended up with 4 yellow films

pentaxuser · Apr 20, 2018

If you can't/ won't mend/get another Jobo( the easy way) then what it requires is experimenting with water in the jug at higher temperatures until you find what is required for the chemicals to be kept at 38. The only problem here is if your room temp changes much from one season to the next. It will work but requires work so to speak

pentaxuser

Truzi · Apr 20, 2018

Test the process with water (no chemicals or film) to get an idea of how fast the cooling is, and maybe set a higher initial temperature to compensate. Put empty reels in the tank, do your process, and measure the water at each step to see where adjustments need to be made. Do this a few times to get a good baseline.

What I did with C-41(and will do with E-6) was use a large amount of water for tempering: a larger mass of water will not lose temperature as fast. I used Styrofoam coolers. I did a few test runs as mentioned above before actually developing film.

I also used aquarium heaters to maintain temperature. Not as good as a purpose-built unit, but worked well enough for me. I let everything (chemicals and all) sit in the tempering bath for quite some time to come up to temperature. I measured the developer temperature by suspending the thermometer half-way in the developer (the middle point). Before pouring developer in the tank, I used a couple changes of tempered water to bring the film/reels/tank up to temp. You'd be surprised how fast a room-temp tank can lower the temp of your developer.

Between agitations I returned the tank to the tempering bath to maintain temperature.

jim10219 · Apr 20, 2018

If the temperature is consistently between 36 and 36.5, then I'd say your system works. You just need to up the temperature of your bath to compensate. As long as your getting consistent results, you should be able to work with it.

I second the recommendation for the aquarium heater. They're cheap, easy to find, and should work well enough for what you're trying to do. It's not only easier, but a more consistent method for keeping the water warm versus monitoring and pouring in hot water as needed. Just make sure the water cycles, so you don't get a hot spot by the heater, and a cold spot on the opposite end.

thuggins · Apr 20, 2018

You're both over thinking it and testing incorrectly. First, it takes some time to get everything at thermal equilibrium. I use an insulated cooler as a water bath to hold the chemicals, developing tank, circulating pump and agitator. The water starts at about 110F and is allowed to drift down till it gets about 102F; this takes an hour or so. At this point it is certain that everything is at equilibrium, but there will still be minor variations (up to a degree) depending on where the temperature is checked in the bath (I use an infrared, non-contact thermometer). Once the developing tank itself (stainless steel) reads about 101.5F I start to load the reel. The water for the prewash is right from the bath (the developing tank is immersed in it). During prewash the tank is back in the bath to maintain temperature. By the time the first developer is introduced and the tank is put back in the bath, a reading from the submerged surface of the tank is reading at about 101F or a fraction of a degree less. I have done nearly 100 rolls of E6 this way and have never had a single problem.

Stop pouring out the chemicals and then measuring the temperature. The very act of handling and pouring out the chemicals will reduce the temperature; that's why everything goes back in the water bath to bring it back to equilibrium. Just try to keep the bath at the high side of 100F (38C should be perfect) during the first developer and you won't have any issues. The temperature of the CDEV and BLIX is not as important.

If you are getting yellow film, you have another issue. Have you checked the accuracy of your thermometer? Are you using distilled water to mix your chemicals? What kind of film are you using? That Lomo stuff can be very yellow. Try using Provia for known color consistency. Incorrect color would seem more likely to be an issue with the CDEV, which, again, is not overly time or temperature dependent. Problem with the first developer will likely show more with lightness, darkness and contrast.

John51 · Apr 20, 2018

One of my hobbies is homebrew and those that craft their own beer need precise temperature control for the mashing process. The digital thermostat they often recommend has the brand name Inkbird. This is far better than the T/stats in old equipment, which are bimetal switches and have a large degree of hysteresis. (The difference in temps between switching on and off.)

Joel_L · Apr 20, 2018

I did a homebrew tempering bath with a suitably size tupperware type tub with lid. Used an aquarium heater ( modified to get higher temps ).. Cut the lid to fit various bottles and tanks. Never got around to adding the pump, but that was on the list. Basically a clone of Jobos tempering bath.

Curious why the Jobo keeps dying.

Berri · Apr 20, 2018

what about a heater? I ordered mine from the imaging werehouse in UK and it's brilliant at keeping the temperature

DREW WILEY · Apr 20, 2018

You also have to be conscious of ambient room temperature and solution volumes. If the surrounding temperature is noticably uncomfortable to you, either too hot or too cold, that should be a warning sign. And larger solution volumes at correct temperature to start with will obviously hold this temperature longer than small volumes, even if you use the "drift-by" temp method based up the average of before and after. Jobo tanks can be a bit finickhy because they fill and drain relatively
slowly and are somewhat thin. You could wrap them with material similar to water pipe jacketing is your processor itself will allow a bit more drum diameter. And you
should always pre-heat the drum and print prior to development with a minute or two of correct temp plain water. If you can land an official Jobo tempering bath at a
reasonable price, do it.

mshchem · Apr 20, 2018

I have processed a lot of E6 with immersion heaters or Aquarium heaters. I have a Jobo CPP 2 that I bought for 150 bucks and cleaned up. I'm not sure I have seen any difference. For the last 20 years I have kept a microwave oven in my darkroom that I use VERY CAREFULLY to warm chemistry in seconds. Waiting for a Jobo to heat up and warm chemistry is not for me . Doran/DevTec made a 700 watt immersion heater, those things work great. As noted by Drew ambient temperature has to be reasonable. I remember developing Cibachrome (85F?) in tubes ,I would stick the tube underneath my t-shirt to warm up the plastic. Get a Doran immersion heater and a 5 gallon pail, once calibrated you could leave your 1 L bottles to equilibrate overnight. If it's cold winter day I turn on my two big print dryers get the darkroom nice and cozy warm .
Mike

Kilgallb · Apr 21, 2018

I got a soul vide circulator pump that keeps temperature within 0.5 degrees. Works great.

WilmarcoImaging · Apr 21, 2018

The game here is to balance the chemical temperature on the knife that is 38 deg C. The force pushing the balance toward lower temp is heat transfer to ambient (the room). The force pushing the balance toward higher temp is energy supplied by a jug of hot water (hotter than 38 deg) or an electric energy input device. Energy out must equal energy in.

A heater is equally implemented with a volume (jug) of water hotter than process temperature, or an electric device (aquarium or cooking heater). Easier imo to use a jug of hotter than process temperature water.

Use the largest volume (mass) of water you can for the tempering bath and for the heat emitter.

Use insulation (eg a foam box).

Experiment and share your results.

mshchem · Apr 22, 2018

Kilgallb said:
I got a soul vide circulator pump that keeps temperature within 0.5 degrees. Works great.

That's great. Good idea

John51 · Apr 22, 2018

Joel_L said:
I did a homebrew tempering bath with a suitably size tupperware type tub with lid. Used an aquarium heater ( modified to get higher temps ).. Cut the lid to fit various bottles and tanks. Never got around to adding the pump, but that was on the list. Basically a clone of Jobos tempering bath.

Curious why the Jobo keeps dying.

Once you're ok with modding an aquarium heater, the possibilities are huge.

Set the heater much higher than you need. Then the internal bimetal T/stat never turns it off and you control the heater using a light dimmer. If the room sucks out 0.1'C per minute from your water bath, the heater adds +0.1'C per minute of heating. Not exactly set and forget, more like keep an eye on it and it gives set and forget results. The closer you control your room temps, the closer the tolerance in your water bath.

Curious why the Jobo keeps dying.

Me too. Permanently dead is binary. Fix it or bin it. Keeps dying implies that it also keeps working in between death cycles. Something is loose somewhere?

ludwighagelstein · Sep 17, 2018

Joel_L said:
I did a homebrew tempering bath with a suitably size tupperware type tub with lid. Used an aquarium heater ( modified to get higher temps ).. Cut the lid to fit various bottles and tanks. Never got around to adding the pump, but that was on the list. Basically a clone of Jobos tempering bath.

Curious why the Jobo keeps dying.

Can you elaborate a bit on how to modify an aquarium heater ? I have an inkbird thermostat which is pretty accurate, the only problem is consistent heating. For heating I used an immersion coil, but it gets too hot, too quick.

REAndy · Sep 17, 2018

Kilgallb said:
I got a soul vide circulator pump that keeps temperature within 0.5 degrees. Works great.

+1 These work great!

Nodda Duma · Sep 17, 2018

Controlling temperature is so trivial that really the only limitation is unfamiliarity with what’s available to provide that control.

A water bath keeping temperature at the exact required temp really only requires:

- A container (Your sink or food serving pans work great)
- A controller with temp sensor: https://www.amazon.com/Inkbird-Electronic-Temperature-Germination-Controlling/dp/B01486LZ50
- Something to sufficiently heat the water : https://www.amazon.com/gp/aw/d/B076...8&pi=SL110&dpPl=1&dpID=41Sk5-KjNIL&th=1&psc=1
- Something to circulate the water for uniform temp: https://www.amazon.com/Homasy-Subme...coding=UTF8&psc=1&refRID=C0664NZKH2E53AFRN7TC

This setup works really well and isn’t very expensive. The specific components make only one of many different possible configurations...there’s many different ways to skin this cat.

Sirius Glass · Sep 17, 2018

Why don't you contact http://www.darkroomdoctor.com/ about your Jobo problem?

twelvetone12 · Sep 17, 2018

Thanks! we actually ended getting in touch with CatLabs and got the spare parts there, first trial is scheduled this week!

Greg Heath · Dec 11, 2018

I am using the Sansaire Sous Vide water heater. So far so good. I use to use a bucket of hot water and hoping everything would work.

koraks · Dec 12, 2018

OP, your jug looks a bit small. Try a bigger tub so that its temperature buffering ability is larger. With a small jug like you're using you'll see much more temperature drift than with a much larger volume. Try a water jacket with a capacity of one or two gallons instead of something like a quart.

WilmarcoImaging · Dec 13, 2018

Temperature stability will be further improved if an insulated box is used. For example, an inexpensive styrofoam cooler.

Process Temperature Control

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