If you’re a tray developer, this might raise your temperature

[Doremus Scudder]

Repeatability, repeatability, repeatability. If you do everything the same way every time, you will include all the variations in temperature, evaporation, etc. If you test to the method, you will have predictable results (within working parameters, of course).

It is quite possible that the temperature of the developer solution rises a bit due to heat from my hands, but if that is a constant, then I don't have to worry about it, just repeat it. It is also possible that evaporation cools the solution somewhat. Unless the relative humidity where I work changes significantly, however, the effect should also be similar each time and, therefore, negligible.

The trick is to try to keep the conditions the same from day to day. So, hot summer darkrooms vs. cold winter ones are a problem for some, I imagine. I'm lucky enough that I can keep my ambient air temps between 20° and 24°C most of the time. (A climate-controlled darkroom would be a great thing to have, though.)

In my U.S. darkroom, I use a Zone VI compensating developing timer. It works well, changing the time as temperature varies. However, I notice this most when printing in the summer, when the print developer temperature rises considerably over a session.

When developing film, even in the summer, the temperature rise is much less, since the developer gets mixed right before use, sits in a tray inside a larger tray with the same temperature water in it, and only gets used once. 18 minutes tops (and that's for N+3, which I don't need that much). In Vienna, I just use a simple timer and make sure to try to develop when my ambient temperature is as close to the processing temperature as possible. Again, a water-bath tray is used.

The difference in temperature rise for a liter of solution over 15 minutes in ambient temperatures of 20° and 24°C is negligible. Let's say, for a 15-minute development time at an ambient temperature of 21°C, that the rise in the developer temperature due to hand-heat is indeed 4°C as Steve Gledhill states (and I might question that result... and, a water-bath must attenuate this effect by quite a bit). Now repeat this at an ambient temperature of 24°C. How much more will the temperature rise?

Here's my test: Ambient temperature, 21°C. I filled a room-temperature tray with 500ml of 14°C tap water, set it on the kitchen counter without a water-bath and let it sit for 20 minutes exactly. I swished my hand in it once every minute just for good measure (although I was not testing the effect of hand-heat, I did think that agitation should be approximated in the test. However, by doing this, I probably introduced some hand-heat). The beginning temperature difference was 7°C After 20 minutes, the temperature of the solution had risen to 15.2°C; a temperature increase of 1.2°. This without water-bath and using room-temperature vessels to measure and pour into. The effect of a 4° difference in ambient temperature would be significantly less over this time period, plus developing times are usually less than 20 minutes.

I would estimate that change from a 4°C difference in ambient temp over a 15-minute developing time would be right around 0.5°C (or less), i.e., significantly less than a 5% increase in development according to my temperature-compensation chart. The question is, is this within working parameters? I suspect so, for most of us shooting black-and-white film.

Bottom line, be repeatable, be repeatable, be repeatable...

Best,

Doremus Scudder

[Heroique]

These are splendid experimental insights – I suspect even the best darkroom scientists fail to consider them when aims or conditions warrant.

I noticed that no film was cooking in your personal test (as it was in Steve’s), eliminating the possibility of any heat-producing chemical reaction adding “kick” to your thermometer – especially w/ a volume of 500 ml. I’m curious if readings might have been different when processing, say, a 4x5 sheet? A small stack of them? What about a different emulsion/developer? I’m also curious if you think these considerations might be more significant in Vienna, where you have no Zone VI timer to compensate for them.

Thanks for being our careful, white-coated scientist!

[jeroldharter]

I don't use trays. I use a Jobo drum on a roller base. But I still have the same temperature fluctuation issues.

I calibrated my development times with solutions in a water bath at 68 degrees, pre-tempering the plastic drum in 68 degree water, and with an ambient room temp of 68 degrees. Now, I keep my solutions in a tempered water bath at 68 degrees and just pour them in the drum. In a second Jobo plastic drum base, I add a liter of the same tempered water in which is the temperature probe for the RH Designs Processmaster timer which works like the Zone VI. So any fluctuation in water temp inside the processing drum should be simulated in the second drum base and compensated by the temperature probe. It seems to work very well. No problems with inconsistency.

[Thebes]

I've never measured it, but my developer becomes noticeably warmer when I tray process, more so for 4x5 than 8x10. It stands to reason that this is reasonably repeatable so it should be controlled by your calibration... at least it should be repeatable if room temp, chem temp and volume, and your technique are the same each time... my life isn't so ordered.

I don't worry about it though, recently I've been developing in tray by inspection. I have sometimes worried about my (water) stop being colder enough to reticulate, this has never happened, but it feels considerably colder when I put films into it

[Jim Fitzgerald]

I use trays for 11x14, 8x20 and 14x17 in Pyrocat-HD. I DBI so no problem at all. I can see when it is done!

[Bill Poole]

I have an 8X10 tray that I have divided down the middle and use to do 2 5x7 sheets at once. I agitate by rocking the tray gently and pretty much continuously. Whether the temperature goes up or down depends on the ambient temperature in the bathroom -- er, darkroom. In the winter, my home temperature usually runs a few degrees lower than 20 degrees C, so I expect the temperature to drop. So I use standard electric heating pad under the developing tray, wrapped in plastic and with about ten sheets of newspaper between the plastic and the tray. I warm up the tray a little before I put in the developer. I usually turn the heater off about half way through the run. Seems to keep the temperature at 20 degrees average +/- a few tenths. Not elegant, but neither am I.

[Doremus Scudder]

Heroique,

My test was not to measure how much heat either hands or chemical reactions added or subtracted from the solution, rather to get an idea of how much a different ambient temperature affected the entire process. From my down-and-dirty test, I think any change due to ambient temperatures being +/- 5°C from the temperature of the developer is negligible.

That means, if you do everything the same way every time, regardless of whether you get or lose heat from hands, chemical reactions, evaporation, etc., etc., you will have repeatable results, since whatever variations in temperature are repeated every time. In the end, that's all that interests me.

If I test for film speed and development time, and use the same technique each time for each different development, I'll be well within my working parameters.

One note on the Zone VI compensating developing timer: If you use one, and the developer temp does rise during the course of development, then the indicated developing time on the timer will really be shorter than the actual time due to the shortening of "seconds" by the timer as the temperature rises above the standard.

If you test with the compensating timer and then develop your negs at that same "time" with a regular timer or clock, you will likely be developing longer. This is why I have different developing times for Vienna, where I develop with a regular timer (or a metronome sometimes) and Oregon, where my compensating timer lives. FYI, the times are about 5-7% different. Water hardness also plays a role in that figure as well.

I'm quite confident I'm getting repeatable results developing with or without my compensating timer; even more so now that I've done the quick ambient temperature test. That is for black-and-white negs tray developed. If I were doing color, I would probably want more control.

Best,

Doremus Scudder

[Bruce Barlow]

+1. To quote my god friend Bruce Barlow, "you will have to pry mine from my cold, dead hand."

I think I like being a "god friend." Shouldn't it be capitalized?

Yup, Compensating Timer. For printing, I even put the developer tray in a warm water bath, just to speed things up. Wouldn't do that with negs for fear of reticulation, but prints seem to be just fine.

[Heroique]

...I use standard electric heating pad under the developing tray...

Now I know what “cooking the film” really means!

I’ve been surprised how many people see falling temperatures in their developer solution – the “evaporation effect” was a noteworthy surprise – and it’s interesting to learn how they keep the thermometer “up” or rely on a means of compensation.

[Bob Farr]

Hi,
Have read these posts with great interest and thanks to those of you who have gone through the testing procedures. I have been using a Zone VI compensating developing timer for years for paper and film. Have not noticed a problem using it.

Am wondering if anyone has tried the RH Designs version??

Bob