Water Bath for temperature Control - benefit is marginal

Steven Lee · Oct 20, 2022

I got my fancy certified thermometer in the mail this weekend with ±0.03°C precision, and decided to have some fun re-evaluating my C41 process. Specifically, I wanted to see what effect the water bath has on the temperature.

So I ran an experiment:

Pre-warm the 1L JOBO tank with 3 reels loaded with fogged film by filling it with 101F water twice.
Run a simulated 3:15 development cycle using 500ml of "developer" in a rotary processor with a water bath
Run the same cycle without any water in the bath

I ran each of them twice just in case to average out small variations (there were no variations). My ambient was 72F. The results are:

Water bath. Starting temperature in the bottle 101F. Final temperature in the tank after "development": 100.1F. Total temperature drop of -0.9F
No water bath. Starting temperature in the bottle 101F. Final temperature in the tank after "development": 99.8F. Total temperature drop of -1.2F

Next, measured the temperature drop caused simply by pouring the developer from the bottle into the tank.
It was 0.4F. This means the in-the-processor drop was 0.5F with the bath and 0.8F without, a paltry difference of just 0.3F

Looks like it is trivial to achieve 100F average dev temp without using a water bath simply by staring with 100.6F

This may look different with significantly lower ambient though.
Just sharing.

albada · Oct 20, 2022

Steven Lee said:
Looks like it is trivial to achieve 100F average dev temp without using a water bath simply by staring with 100.6F

To check my understanding of the 100.6F, the initial pour-in drops the temperature by 0.4F, making it 100.2F. At the end of development, temperature has dropped another 0.4F, making it 99.8F. The temperature range is 99.8-100.2, and thus the average temperature of development is 100.0F. Did I get that right?

koraks · Oct 20, 2022

Steven Lee said:
Looks like it is trivial to achieve 100F average dev temp without using a water bath simply by staring with 100.6F

I think that's correct. The main issue I would see is that the numbers work out differently depending on ambient temperature, tank material, dry tank mass and developer liquid volume. Some of these factors may only be a small influence, the others will be larger. You'd have to test a couple of common scenarios for your use to "calibrate" the temperature.
But if you do so, I find it's quite conceivable that it'll work very well indeed.

AgX · Oct 20, 2022

Kodak once gave out a data sheet devoted to do processing without waterbath, but with raised initial bath temperature.
I have not got it at and, but the basic idea likely is to have an initial temperature, that yields together with the final temperature an average one that is same as the standard one.

snusmumriken · Oct 20, 2022

Did you pre-warm the tank in both cases, with and without the water bath? I think the tank itself has an appreciable thermal capacity (a Paterson tank certainly has). So I would expect that if development time is short, as in your case, the outside water bath would contribute little.

It is worth considering that the thermometer itself has some influence on the system you are measuring; also that it takes a finite time to reach an equilibrium reading. I don't know whether you have taken those things into account? I have experience of both effects when measuring fluctuating core temperatures of living animals on a similar timescale.

AgX · Oct 20, 2022

If you really have issues with a thermometer getting up to temperature in time, then store it in a tempering bath close to the temperature you are goung to meter.
Mercury stem thermometers are very fast, a high-accuracy digital thermometer needs 2-3sec, dependant on probe-stem thickness.

Don_ih · Oct 20, 2022

It will be different processing paper. The tank is much larger, the air volume much greater, the liquid volume much smaller. But it makes sense with film. You could just run hot water over the loaded tank for a few second before pouring in the developer and your temperature would stay pretty close to correct through the short development cycle.

Don_ih · Oct 20, 2022

However, I consider the main value of the Jobo water tub its ability to keep the developer in the storage bottle at the correct temperature.

halfaman · Oct 20, 2022

Steven Lee said:
This may look different with significantly lower ambient though.

I think this is the key for having a Jobo machine: Don't care about the ambient conditions. Jobo CPP/CPA can even cool the tempering bath during hot summers if solenoid water intake is used.

sillo · Oct 20, 2022

How long did you prewarm the tank for?

pentaxuser · Oct 20, 2022

Steven you mention a Jobo tank so can I take it that his was all done in a Jobo processor with the water bath at the right temperature?

If it was then it would seem that the drop in temperature is marginal without the pre-warm and may not be needed. It has been a while since I processed C41 in my Jobo processor but if I recall correctly then when I started my journey into C41 I simply got the water bath temp right and had the dev, and blix sit in it and had a room temp much as yours or may be even 1 degree C less and the film processing was fine

pentaxuser

koraks · Oct 20, 2022

pentaxuser said:
Steven you mention a Jobo tank so can I take it that his was all done in a Jobo processor with the water bath at the right temperature?

Have you read this:

Steven Lee said:
Run a simulated 3:15 development cycle using 500ml of "developer" in a rotary processor with a water bath

Run the same cycle without any water in the bath

pentaxuser said:
If it was then it would seem that the drop in temperature is marginal without the pre-warm

This wasn't about a pre-warm. It's about the water bath itself. See also the thread title; it's kind of a give-away in this case.

Steven Lee · Oct 20, 2022

snusmumriken said:
Did you pre-warm the tank in both cases, with and without the water bath? I think the tank itself has an appreciable thermal capacity (a Paterson tank certainly has). So I would expect that if development time is short, as in your case, the outside water bath would contribute little.

It is worth considering that the thermometer itself has some influence on the system you are measuring; also that it takes a finite time to reach an equilibrium reading. I don't know whether you have taken those things into account? I have experience of both effects when measuring fluctuating core temperatures of living animals on a similar timescale.

Yes, I pre-warmed the tank using Photo Engineer's (Ron Mowrey) algorithm (filled it with 101F water twice, for 1 min each). The entire time I kept the thermometer submerged in 101F water between measurements to get the final reading quickly. <--- @sillo

pentaxuser said:
Steven you mention a Jobo tank so can I take it that his was all done in a Jobo processor with the water bath at the right temperature?

Yes, I keep the water bath in the processor at 101F

pentaxuser · Oct 20, 2022

Quite right koraks. I need to read posts more carefully.

pentaxuser

MattKing · Oct 20, 2022

I tweaked the OP's spelling of Photo Engineer's (Ron Mowrey's) name .
And I'm tweaking the thread title, because of the pedant in me

Steven Lee · Oct 20, 2022

@MattKing if I upload a photograph into "street photography" thread, are you going to swap it with your version of it as well? I am asking it half-jokingly, because language is no different from a photo. Both are intellectual property and a form of self-expression. I do not mind you re-writing my title, I am pointing out that others might.

MattKing · Oct 20, 2022

Steven Lee said:
@MattKing if I upload a photograph into "street photography" thread, are you going to swap it with your version of it as well? I am asking it half-jokingly, because language is no different from a photo. Both are intellectual property and a form of self-expression. I do not mind you re-writing my title, I am pointing out that others might.

We use titles to help the forum run, and we try to make sure that it is easy for people to find things. One of the problems with your initial title is that water baths are also used for other purposes than temperature control, so it could have confused people looking for other things. Thus the change adding the reference to temperature control.
As to the rest of the change, I think your posts actually point to a marginal benefit, rather than a dubious benefit, but if you want that part changed to "benefit is dubious" I'm happy to do so.

Steven Lee · Oct 20, 2022

@MattKing There is no "we" when it comes to creating content. This was my post, my experiment, my conclusions and my choice of words. Same as with making a photograph. I have done the work and donated the results to this community. You and I are not a team.

Replacing the results of someone else's effort because you prefer your choice of words is no different from uploading your photos instead of someone else's. Absolutely no difference. Moreover, I care about the quality of my work. The destroyed title was far better because it was concise and matched my conclusion. The new title is too long and it describes your conclusion, not mine. Nothing in what I wrote is "questionable". I am a perfectionist and I don't share "questionable" conclusions. You misrepresented my work on my behalf.

I appreciate your good intentions though. The health of online communities often hinges on a just a few individuals like yourself who care. I only wish you pointed your energy on something less questionable and more useful. Have you considered aggressively locking discussions that have 10+ pages and have gone off-topic? There's plenty of wisdom in the archives deeply buried in "mega-threads" with irrelevant titles.

[EDIT] No need to change titles or chew on this any longer. It's not a big deal. Moving on...

MattKing · Oct 20, 2022

For the community in general - if one of us changes one of your thread titles to improve the usability and searchability of a thread - particularly for those who access Photrio on a cel phone - and you would prefer a different choice of words, please don't hesitate to make the request.
I'll leave my disagreement with Steven Lee about the meaning of "dubious" where it stands.

Don_ih · Oct 20, 2022

To be fair, when I first saw this thread I wondered if it was about pre-soaking or a water-bath for developing. Looking at it answered the question.

But, also to be fair, Matt does interject his sensibilities a bit too much. But I'm possibly one of those curmudgeons.

MattKing · Oct 20, 2022

Possibly However, that group description might include me too.
I'll give this to the OP - it wasn't even close to one of those infuriatingly vague and unhelpful Thread Titles like: "Question about Film".
And more importantly, it is an excellent thread, beginning with an excellent post.

DREW WILEY · Oct 20, 2022

The key to drums is sustaining the correct temp INSIDE the drum. Jobo tanks fill slow and drain slow, and have thin walls. So either a surrounding water bath or compatible ambient temp is potentially important. It also depends on several other variables, including pre-tempering the drum, volume of solution inside, duration of the development phase, and just how fussy a given film or paper medium is.
What someone might get away with on a mild day could well backfire in an excessively hot or cold darkroom setting. That's common sense. For minor before/after temp issues, a drift-past model is appropriate, starting above a recommended temp just enough for the average between that and the end temp is right in the middle.

All kinds of devices are available at a price for precise temp control. For RA4 processing, I simply use a basic Jobo tempering box by itself to maintain the solution bottles at the correct temp in advance. For really nitpicky color separation film work, I have on hand an expensive 1000W thermoregulator good to within 1/10F, but rarely need it. I'm about to stuff it in the back of some cabinet. I also have a serious darkroom water mixing valve laying around somewhere, but have been too lazy to permanently install it. For film and paper trays, I simply use a Zone VI compensating temp probe. My favorite thermometer is the venerable Kodak Process Thermometer, Type III I think. Electronic thermometers are just too slow to read, and need to be repeatedly recalibrated. Unless those are obtained from a scientific or true lab supplier, I'm very suspicious of many of the accuracy claims.

pentaxuser · Oct 20, 2022

Don Heisz said:
To be fair, when I first saw this thread I wondered if it was about pre-soaking or a water-bath for developing. Looking at it answered the question.

Yes while not wishing to retract my earlier admission that I had not read the text as assiduously as I ought to have, I fear that I suffered from the same erroneous conclusion that a water bath was bathing film on water prior to the process i.e. pre-soaking

pentaxuser

mshchem · Oct 20, 2022

Steven Lee said:
I got my fancy certified thermometer in the mail this weekend with ±0.03°C precision, and decided to have some fun re-evaluating my C41 process. Specifically, I wanted to see what effect the water bath has on the temperature.

So I ran an experiment:

Pre-warm the 1L JOBO tank with 3 reels loaded with fogged film by filling it with 101F water twice.

Run a simulated 3:15 development cycle using 500ml of "developer" in a rotary processor with a water bath

Run the same cycle without any water in the bath

I ran each of them twice just in case to average out small variations (there were no variations). My ambient was 72F. The results are:

Water bath. Starting temperature in the bottle 101F. Final temperature in the tank after "development": 100.1F. Total temperature drop of -0.9F

No water bath. Starting temperature in the bottle 101F. Final temperature in the tank after "development": 99.8F. Total temperature drop of -1.2F

Next, measured the temperature drop caused simply by pouring the developer from the bottle into the tank.
It was 0.4F. This means the in-the-processor drop was 0.5F with the bath and 0.8F without, a paltry difference of just 0.3F

Looks like it is trivial to achieve 100F average dev temp without using a water bath simply by staring with 100.6F

This may look different with significantly lower ambient though.
Just sharing.

Excellent report. I used to warm up my old Paterson tank by putting in under my t-shirt for a couple of minutes

Too many people shy away from color work for fear of temperature control. You have shown quite clearly that pre-heating the chemistry and the tank is the key. It's dubious whether the marginal benefits of a processor is worth the cost.

Thanks for sharing.

halfaman · Oct 21, 2022

Drew mentioned some interesing thing. If anybody thinks temperature is not so hard to maintain during C41 development imagine in RA4 that it is 4 times shorter (45 seconds). Come on! There are no excuses to not print!

Water Bath for temperature Control - benefit is marginal

Steven Lee

albada

koraks

Moderator

AgX

snusmumriken

AgX

Don_ih

Don_ih

halfaman

sillo

pentaxuser

koraks

Moderator

Steven Lee

pentaxuser

MattKing

Moderator

Steven Lee

MattKing

Moderator

Steven Lee

MattKing

Moderator

Don_ih

MattKing

Moderator

DREW WILEY

pentaxuser

mshchem

halfaman

Water Bath for temperature Control - benefit is marginal

Moderator

Moderator

Moderator

Moderator

Moderator

Moderator

Privacy & Transparency

Privacy & Transparency