Temperature rise in tank?

I would like to raise an issue that has been discussed occasionally but not resolved, as far as I can see.

When I develop film in a Patterson tank, the temperature rises by 1C/2F within a few minutes. I keep the tank in a bath which remains at 20C/68F. All water comes from jugs, which also keep the same temperature. My ambient room temperature is 21C/70F, ie same as the elevated temperature.

I do 2-4 inversions each minute, holding the tank by the edges of its lid. My most commonly used developer is XTOL. I don't see this effect when I am processing at temperatures above ambient. I hear people are getting this effect with steel tanks too.

I don't know what causes this rise, and I usually compensate by reducing development time to avoid overdevelopment.

Does anyone have a good explanation as I would like to be able to keep a constant temperature, if I can?

Steel tanks are more susceptible than plastic ones.

I use Paterson tanks and have never noticed a rise but then I never check the temperature of the developer when it is in the tank nor when it comes out of the tank.

Personally, I would not concern myself about this. Far more important is that you use a consistent and repeatable development regime. If the developer ALWAYS rises by 1˚C and the negatives are fine then just keep repeating what works. If your negatives are overdeveloped then adjast accordingly and STICK to the new time.

Bests,

David.
www.dsallen.de

I believe that the reduction of silver halide by Quinones is an exothermic reaction, so yes, it would make sense that the chemical temperature would rise during development.

Do you replace your developing tank in the water bath between agitations?

I personally develop in a Jobo tank, where the ratio of surface area in contact with the water bath to the volume of developer is quite high, so I suspect that the reaction is less - but then, my more vigourous agitation would work in the other direction. The most important thing is to always do things the same way so that you get consistent results, and can adjust your own time/temp to the process that gives you predictable results.

The actual temperature of that DRY tank has a LOT to do with what temperature you think has now taken place. Most likely the 'temp rise' took place within the first five seconds as that (relatively) cool liquid hit the (relatively) warm plastic (and reel).

What Mark_S said about exothermic reactions is interesting but I will conger that that is not the cause. (At least I have never found that to be the case.) David Lyga

Thanks for the replies. I do put the tank back in the bath between agitations. I also presoak the film in the tank at process temperature, so the difference between the tank and the developer is minimal to start with.

The exothermic explanation certainly seems plausible, as the jugs with the chems don't rise in temerature despite being placed in the same bath as the tank. The water jugs are placed to the side of the bath and don't rise noticeably during the process either.

Initially I saw some overdevelopment from it, but now that I have reduced developing time, it's fine. I'm just curious to know.

1C is 5%. Can you tell the difference between N + 5% and N-5% with out a densitometer? How do you compensate for 5% over 10-12 minutes? 30 seconds less at the end of a run?

Most likely the variation between thermometers used is greater then 5%, and not in a consistent manner.

+1. I have never noticed an issue with printing negatives processed with a rise in temperature which I have developed in steel tanks. I have two old Weston dial thermometers which both read the same. Whither they are actually accurate has never been an issue. I think consistency in your process once you are getting your desired results is more important. I wonder how much the masters of photography worried about a degree here or there. Many great images were made before light meters, batteries,coated lenses and all the other goodies we have available. Don't get me wrong our current technology and equipment is terrific. While I strive for the best image I can make, I prefer not to get too hung up on chasing such a minute detail.

Personally, I use the same three films and either of two developers and only vary from my "standard" routine of exposure and/or development time is needed because of the (available) lighting conditions or subject matter call for tweaking.

just a toot of my own horn... I had a photograph selected for the Hasselblad Bulletin website Feb edition"Around the World". (a second time for me)

http://www.jeffreyglasser.com/

Why not try elimination of one factor. Go though the motions of developing a film (use plain water at the same temp.) but with no film in the tank. If the temp still rises then it is an outside factor, if it doesn't, then, yes the film may have some effect.

Jaf-Photo said:

Thanks for the replies. I do put the tank back in the bath between agitations. I also presoak the film in the tank at process temperature, so the difference between the tank and the developer is minimal to start with.

The exothermic explanation certainly seems plausible, as the jugs with the chems don't rise in temerature despite being placed in the same bath as the tank. The water jugs are placed to the side of the bath and don't rise noticeably during the process either.

Initially I saw some overdevelopment from it, but now that I have reduced developing time, it's fine. I'm just curious to know.

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For peace of mind, why not just standardize on 70 degrees F? It's easier to read on your thermometer too.

Thomas Bertilsson said:

For peace of mind, why not just standardize on 70 degrees F? It's easier to read on your thermometer too.

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if your thermometer reads in Celsius, that might not be so easy, but in any case why is 20 hard to read then 70?

CatLABS said:

if your thermometer reads in Celsius, that might not be so easy, but in any case why is 20 hard to read then 70?

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Gosh darned it, you are right. Unless you use degrees Fahrenheit, of course, in which case 70 is easier than 68. (Particularly for guys like me with really poor eye sight).
If it's in Celsius, well, then 21*C it is.

Either way, the important question of the OP's inquiry has to do with temperature drift. If it drifts from 20*C to 21*C every time film is processed (which coincides with the ambient room temp), it seems logical to settle on whatever that temperature is rather than trying to fight it. If 1*C = 5% or 10% then just decrease development time by that amount. Done.

Thanks again for excellent suggestions.

I will actually run a cycle without film to see if I get any temperature drift. I just didn't think of that

It also makes a lot of sense to adjust to ambient temperature of 21C/70F as I can use the chems straight out of the bottles without a bath. Why didn't I think of that?

My thermometers show both C and F so that's not an issue (and I have gotten rid of the inaccurate ones).

The reason I usually run at 20C/68F is probably that my old photography teacher was very strict about that. Old habits die hard, I guess.

Again, thanks for pushing me out of my set ways.

I'm wondering how you know the temp has risen? Did you open the tank and get a reading, or pour it out into another container and get one? Was your tank the same temp before you poured the chemical in? It makes sense that the temp would rise if you are inverting the tank, as all that energy of the fluid sloshing around has to be converted into something, and heat would be my guess.

I discovered it by reading the temp at the start and end of development. It was a carry over from C41. Then I took some readings during developmen and found that the temp rose quite quickly by 1C, in about 3 minutes. Then it stabilised, rising only slightly.

Maybe I should do a test for OCD?

You didn't mention whether or not you ware gloves when you run film. I'm sure that the rise in temperature can be attributed to your bare hand coming into contact with the tank. I always put on Nitril gloves to keep that heat transfer under control!

"I have gotten rid of the inaccurate ones"

How did you determine which ones were accurate? Do you use more than one when your developing?

I wear thick vinyl gloves when developing and I only grip the rim of the lid, never the tank itself. So I think the heat transfer from my hand would be limited.

I use calibrated thermometers and get rid of the ones that deviate. I use different ones for chems and water to avoid mixing.

The reason for those things is that I had a very strict teacher in darkroom technique, who emphasised control and consistency. I mean, you'll get usable negatives even if you mess about with times and temperatures. But to use the film to its full potential, it's important to be meticulous.

I started out with the big "glowing face" bi-metal thermometer and used it for years. It could also be adjusted/calibrated if needed. A couple of years ago I was given a bunch of darkroom junk and in one box was an Omega digital darkroom thermometer. I thought I had the world by the tail. I checked it against the bi-metal one I had and it was I very close. I mounted the unit on the wall in front of my sink with the corded probe at the ready. To make a long story short the Omega digital started acting erratic. The only problem with that is that you don't know it's acting erratic! It took me some badly developed film before I traced it to the stupid thermometer. It went in the trash and out came the Bi-metal one again. Later I stumbled onto an Eastman Kodak SS lab thermometer w/ box like new in an antique shop for $5.00. The rest is history as they say. I learned the hard way, but I do know that the digital was not off by one or two degrees, but by about five or six degrees. Mercury and alcohol filled ones shouldn't very by more than one degree. I have seen some cheap thermometers slip in the yokes that the tube is held by and when this happens your in big trouble. JW

I have raised this question myself without getting an answer to the question. Agreed, the rise will not significantly affect the development. It is all about being consistent and having control of your process. I routinely pour the developer back into a graduate with a thermometer after development to know what temperature the film was processed at. I believe it drifts up slightly during development regardless of measures to hold it at 68.0 degrees.

The practical part of this measurement procedure is you will find that during summer months the drift is higher and more significant probably due to the ambient temperature in the dark room. When it is very warm out you can get a drift of 1-2 degrees despite keeping the tank in a water bath at 68 degrees (especially when using taller tanks in a shallow bath). Two degrees starts getting significant and will happen during hot weather if you are not careful.

So bottom line, measuring the developer coming out of the tank confirms that your process is consistent and avoids second guessing if negatives are over or under developed.