system for keeping temperature constant

I am relearning the process of developing black and white negative film and have encountered a problem which may affect other photographers. For now, I am working exclusively with Tmax 400 speed film and using D76 developer. If and when I get consistent results from it, then I will experiment with other alternatives.

I recently noticed that the temperature of my developer changes a fair amount even during the 8 minutes that I have it with the film in the tank. I poured the chemicals in at 19.8 deg C and (after 8 minutes), the temperature was 21.6 deg C. I called a photographer friend who suggested I get a water bath, which would help keep water temperatures constant throughout the process. He no longer processes film and could not refer me to anything specific.

It sounded like a good idea, but it raises a second problem. I live in the southwest, where water temperatures in the attic are frequently above 110 deg F, and all water pipes go through the attic. This means that in the daytime, you can run your cold water all day and it won't come below 90 deg F. I am looking for a system (if it in fact exists), which pumps water in constantly, measures its temperature, cools it if it is too warm, and pumps it back out again. Preferably, this system is not too large, does not consume too much electricity, and can be put away in a closet.

My questions: just how important is a constant temperature for developing film? Is there such a water cooling system that I envision? If so, where can I find it?

Thanks in advance, Keefe.

A constant temperature is important. However, many who process color and have a temperature control problem use "drift by" temperature. Simply stated average the starting and ending temperature and use that to compute your processing time.
Chillers can be bought, but they are expensive. If a water bath is used it needs to be considerably larger than your film container in order to maintain a temperature.

In trying to keep my chems a consistent temp (I don't have the extremes you do though). I have measured amounts in separate containers and just let them sit and adjust to the room temperature. I've not experienced much temp variation during the development step, but it can depend on what sort of system you are using. If using a tank, and it's steel, this can happen just from handling during inversions. Plastic is less likely to do this.

It doesn't sound like you have an overly large change in temperature, particularly if what you're getting is consitent, that's the key; do everything the same each time (unless you're testing something, then change only one thing at a time). What I do in the summer when I couldn't get water below proccessing temp (though I never had that warm water to deal with). I use ice to bring a big graduate (2 liters or larger, so it has a lot of thermal mass and changes temp slowly) of water to temp, use that to mix my chemicals, I use pyrocat and rodinal at fairly high dilutions, so the stock chems don't signifigantly change the temp, if you do need to bring the working solution, ice in a plastic bag (so when it melts it doesn't change the dilution) works well. I do use a water bath when using a small stainless tank or when it's rather hot. I just use a developing dray or a simple dishpan with water at developing temp and keep a thermometer in the water bath. When it starts to creep up, add some cold water. I've had no trouble keeping temps within a degree this way.

Peter

When I lived in the UK temperature was easy. I just used a bowl of water at the right temperature, and hot & cold water if necessary to compensate for any drift.

Now living by the Aegean I have a winter temp cycle based on 20°C, (same as in the UK), and a Summer warm cycle based on 24°C. A tray of ice-cubes works wonders in very hot weather.

When I made photographic emulsions commercially back in the 70's/80's I made a water cooler by taking the refrigeration/freezer unit & compressor etc from an old refrigerator, not sure that's what you call them in the US, and put the freezer part in a tank, this gave me water at less than 1°C, you only want 20°-24°C which would be very easy, you use the controller from the refridgerator to set the water temperature. Costs nothing yo use a machine that works but is rusty/old/being thrown out.

Ian

Keefe, welcome to APUG

I think we all suffer from temperature changes during development and most cope with it by "Drift Through"

You seem to have a 1.8C temperature increase during your development period and with the nominal target temperature of 20C it means you should aim to start with a developer temperature around 19.1C and end up around 20.9C equally straddling the nominal 20C target

The method is not perfect but close enough not to worry about.

Tempering baths in theory can help with temperature stability but introduce their own difficulties and I am far from convinced they are worth the effort

There is a great deal to be said for the KISS (keep it simple stupid) approach to film processing as consistency is the key to success

Good luck

Martin

Martin

That small change in process temperature isn't going to make a bit of difference when processing B&W...even for Tmax. Don't worry about it.

Yes but I think the OP would be happier if he had just a little more control.

Ian

BradS said:

That small change in process temperature isn't going to make a bit of difference when processing B&W...even for Tmax. Don't worry about it.

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Probably true but I think part of the fun is worrying about and trying to fix/sort out the details.

A water bath has its own issues of control, but the tolerances are usually smaller than "drift" which is dependent on ambient temperature variations.

If you are using a simple tank and inversion processing, then I woould get a 16 x 20 tray, one of the deeper 4 inch deep kind sometimes called a "hypo" tray. In that, place an immersion heater. Dev-Tec makes (or made?) a nice one with a thermostat. A low budget method would be to use an aquarium heater. In the opposite corner of the tray, place a small aquarium pump to circulate the water. This approximates a Jobo processor in a much simpler, cheaper way for an immersion tank. You might need a weight to hold the tank down when at rest. I do this with my BTZS tray, placing in a larger tray as above.

Buying a unit that cools and heats water is very expensive. I haven't seen many for less than $1000, but maybe others can point you to a cheaper unit. An alternative in my scenario is to use the small, re-usable freezer packs designed as substitutes for ice in coolers. Keep some on hand in your freezer and you can immerse them in the water bath briefly if the temp drifts too high.

In cold weather I keep a portable oil filled radiator heater under the darkroom sink. It keeps the temperature right on, I can move it in or out. It keeps me nice and warm too.

On the cheap

I'm in Florida and although my cold water isn't as warm as yours, this matter of controlling temps is really a user of my time and resources. My "cold" water is currently 83 degrees F no matter how long you run it.

I've also observed the temperature drift; it's amazing it is so much. While we may be disposed to shrug it off, I am a victim of being told over and over about repeatability as a foundation to good negatives. And what do you do when your drift isn' what you thought it would be?

I use a simple cheap plastic dishpan that sits inside one half of the kitchen sink. I've tried using the sink half itself, but the steel is so conductive any advantage of having more volume is offset.

I also have a small bowl of cold water with cubes at the ready for when the temperature bumps upward.

I also really am annoyed that my developing is now competing for ice cubes that I really, really need in this abysmal climate!

I monitor my main water bath with a $10 digital thermometer with a remote probe. After every few inversions, I test the tank temperature with a $10 infrared thermometer. If it is starting to climb, into the ice bath for a few seconds. It never seems to drop!

BTW, my mother remembers her father doing this when developing prints in Rio back in the 1920's. And he didn't have an ice maker, it was a block delivered by horse for the icebox. So, yeah, we do have it easier!

thanks.

I'm really impressed and grateful for the amount of feedback given in only a few hours. This seems like a good forum to hang out in.... For now, I've decided to go with the "drift through" formula. If it works for others, it will (hopefully) work for me. I also found a separate chart from Kodak that gives me processing times for slightly warmer temperatures -- as I recall, it has times for 20, 22 and 24 deg C. My thinking is that if the temperature of the chemistry is close to the ambient temperature of the room, there will be less drift over the time the film is in the tank. This thought, however, raises another question: is there an "ideal" temperature for processing Tmax? The chart I found does not indicate a preference.

Another thought is to buy a small air conditioning unit to cool off the bathroom, which doubles as a makeshift darkroom. The house has central air, but I keep it closer to 80deg F and use ceiling fans to stay cool. I can use the small ac unit when I want to process film and pull the room temperature down to whatever is the ideal temperature.

Thanks again, Keefe.

You might also check out the new process timer from RH designs, one of the sponsors on APUG. Their products are first rate. The process timer has a thermometer and adjusts the time variably based on temperature.

My strategy with b&w has been to mix to room temperature. Hence no temp drift. This suits my habit of going away for a few hours for other work or whatever.

Room temp....

keithwms said:

My strategy with b&w has been to mix to room temperature. Hence no temp drift. This suits my habit of going away for a few hours for other work or coffee.

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...is over anything that is suggested. The latter typically peaks out at 75 F, my room temp is 79-83, depending on time of day. Even the chemicals that I keep on the terrazzo (a type of upscale concrete) floor in the bathroom stabilize at 83 degrees. That's sort of ground temp and a bit of A/C.

And even if you adjust for higher temperatures, you start getting into that curse of short development times which leaves little or no latitude for error.

Paul Verizzo said:

...
And even if you adjust for higher temperatures, you start getting into that curse of short development times which leaves little or no latitude for error.

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One help might be to use more dilute developers like TMAX developer at 1:9.

I haven't had any problems dev'ing at 23-24 C and that temp is rock solid in my building (I am lucky). I adjust everything around that. Mind you, if I were dev'ing 35mm then I would probably feel differently, but just about everything I do in b&w is tray.

Some years ago, I started using D-23 in summer as it seemed to me that development times with D-23 were less sensitive to temperature. Now, I use it year round and rarely even bother to measure the temperature of the solution. In the summer the ambient temps inside the house range from about 19 to 32 degrees C. I never think too much about it - except as it relates to my own comfort.

Just did another twelve sheets of FP-4+ in D-23 last night. Again, I didn't even bother to measure the temp....The story would have been different with HC-110 though.

jeroldharter said:

One help might be to use more dilute developers like TMAX developer at 1:9.

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Six minutes is D-76 1:1!

Curt said:

In cold weather I keep a portable oil filled radiator heater under the darkroom sink. It keeps the temperature right on, I can move it in or out. It keeps me nice and warm too.

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I'm doing the same thing, great little heaters. I use a small AC unit to cool things down in summer. I plan ahead and wait for the room temperature & chemicals to stabilize @ 68°f.

You have experienced the influence of hydroquinone

BradS said:

Some years ago, I started using D-23 in summer as it seemed to that development times with D-23 were less sensitive to temperature. Now, I use it year round and rarely even bother to measure the temperature of the solution. In the summer the abient temps inside the house range from about 19 to 32 degrees C. I never think too much about it - except as it relates to my own comfort.

Just did another twelve sheets of FP-4+ in D-23 last night. Again, I didn't even bother to measure the temp....The story would have been different with HC-110 though.

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And the lack of it.

HQ has a much higher coefficient of thermal changes than Metol.

Paul Verizzo said:

You have experienced the influence of hydroquinone...
And the lack of it.

HQ has a much higher coefficient of thermal changes than Metol.

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That was exactly the hypothesis that drove me to try D-23 in the summers. Hydroquinone is sensitve to temps. Metol much less so. Since D-23 is Metol only, I reasoned that it would be robust with regard to temperature variation. And all of my experience with D-23 so far supports this.

Paul Verizzo said:

...is over anything that is suggested. The latter typically peaks out at 75 F, my room temp is 79-83, depending on time of day.

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You might look into tropical developers. These are designed to work at higher temperatures than conventional developers. I believe that Anchell's Darkroom Cookbook, 2nd Edition has a brief section on them. I've never used them, myself; as I live in Rhode Island, I only need to deal with those sorts of temperatures for a couple of months per year (now, for instance).

I didn't know about tropical developers, but I do have some Efke PL 50 M which is labeled "tropical."

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I didn't know about tropical developers, but I do have some Efke PL 50 M which is labeled "tropical."

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Keith that film was made to be used only in the Tropics with a "Tropical" camera and developed in a "Tropical" developer. Did you get the complementary bamboo stirrer with your order?

I bought a lot of the foil wrapped Efke film from JandC and it was all called "Tropical". I inquired around that time but no one could tell me why it was labeled like that. Kodak has had tropical developers for a long time, Ron can probably tell us the history. I believe it was a high temperature low fog developer.

Curt