Here's a curve generated from test data for time vs. print development in an article in PhotoTechniques or Camera & Darkroom, can't find the reference right now. But it's for Dektol with a fiber based paper, and the reference print is 2 minutes @ 68F.
So when is completion? At the end of 3 minutes? At the time
Originally Posted by jeroldharter
of maximum density? Perhaps at the moment of maximum
contrast? Or when it looks right? Dan
First, chemical reactions usually speed up with increased temperature. This means that your developer will work faster when hotter. Many developers (and I would think that Dektol would be among them) react rather regularly to increases in temperature. In other words, if you need to use warmer developer, just develop for a shorter time. The .pdf document linked to above is a good starting point. A predictable increase in activity vs. temperature was the premise behind the Zone VI compensating developing timer, which adjusted the "seconds" of the timer based on temperature; at 68°F one "second" was really one second, at higher temperatures the "seconds" were really shorter, at lower temps, longer, allowing the standard developing time to be retained. (I love my Zone VI timer and would not like to part with it!)
Second, developers do not have to be 68°F to work correctly. Especially when printing in warmer weather, it is often easier to use the warmer, ambient temperature for "standard" rather than worry about cooling everything down. While 88°F (31°C) might be at the extreme end of things, with the right developer, it should be managable. The same applies, but with more necessity for precision and testing at different temperatures, with film, generally speaking. The real problem dealing with different temperatures is that some developers/developing agents/combinations of developing agents do not react linearly/regularly to changes in temperature, i.e., they are difficult to predict and make a nice chart for. These are usually more exotic developers. Nevertheless, they will work at different temperatures. One simply needs to test them at the particular working temperature desired.
There are a number of ways to deal with determining print development time at different temperatures. The Zone VI compensating timer is one (sometimes they are available used). Another time-honored method is the factoral method. Simply note the time it takes for a middle gray tone in the print to emerge and separate from neighboring tones and multiply that by a "factor." I find average factors to be between 4 and 6 usually. Some prints need more development and a larger factor. (As an aside, prints are "completely" developed when maximum black has been reached and the developing rate has slowed significantly. There is no particular point when a print is "done," like a turkey in the oven... You need to have enough development to get the tonalities you want. Longer development with most modern papers basically just speeds up the paper, kind of like adding more exposure.) Back to the topic... The factoral method seems to function well independent of temperature. At higher temperatures, your print will emerge more quickly and developing times will be shorter, but the factors should remain the same. This allows a measure of repeatability at varying temperatures (and a kind of adjustment for changes in developer activity due to exhaustion as well).
Finally, if developing times at high temperatures are uncomfortably short, one can simply increase the dilution of the developer to lengthen the time. Since the amount of stock solution will be less, the developer will have a smaller capacity and may need to be changed more often, but the factor should remain the same.
I develop both film and paper in trays at different ambient temperatures. I rely on my compensating timer to make the adjustments for me with the film. However, I do mix the developer at 20°C and put the developer tray into a larger tray with 20°C water in order to minimize the temperature shift during processing. For papers, however, I just let all the chemicals warm up to ambient temperature, which in the summer can be in the low 80sF. I use both the factoral method described above and my compensating time. I like it that they agree most of the time...
So, go ahead and print at ambient temperature. I wouldn't worry about cooling the chemicals down unless the high temperature was causing physical damage to the prints (emulsion sloughing off, etc.). Use the factoral method and dilute developer to control time and have fun.
Last edited by Doremus Scudder; 05-17-2009 at 06:01 AM. Click to view previous post history.
All the above answers a perfectly reasonable. But , at least in my experience, developer temperature is not all that critical for paper. Anything between 65F (18C) and 78F (25C) seems to work pretty well with the standard developing times. Paper, just like film, develops faster as the temperature goes up. But unlike film, paper development goes pretty well to completion, and there is no danger of overdevelopment. The danger of developing paper too long at a high temperature would be increased fog, and modern papers are very well protected against that.
As nworth said, all very reasonable and useful answers and thoughts. Lee, thanx for the chart; Doremus, a comprehensive and thoughtful response. I'll go about my business as usual, unless things get really cooking around here, in which case I'll think about lowering the development temp a bit. I just had a session last night, and everything is still at 78; there's a noticeably faster time for the image to come up--no surprise there.
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Not really for prints, which should be developed to completion anyway. The only thing I'd really worry about would be developer induced fog. I once tried developing a print in Dektol 1+3 at about 100F. It fogged almost immediately. I think you'd be ok at about 80F. Toning goes faster at warmer temperatures too. With a 2 part sepia toner, the bleach works faster and it's the degree of bleach back that you allow that controls the toning. The redeveloper goes to completion. Selenium toning is controlled by the the strength of the toner, time, and temperature. If the solution is too strong and the temperature too high, toning can proceed too fast and you can over do it. Diluting the toner a bit more will slow it down, allowing you to pull the print when you feel its done.
I have seen photo labs machine develop paper at 85ºf to 105ºf. processing times are 20 sec to 14 seconds.
Great answers, all! The only other thing I would mention is that at higher temperatures, the paper may be more susceptible to damage as the emulsion is softer. I would just say, 'be careful with those tongs!'.
Bruce, that brings up a bit of thread drift on my part. I was reading a book on advanced artsy techniques the other day, can't recall the title or author and don't have the book to hand this moment, but the author detailed a technique for using very hot water to remove (lift) the emulsion after printing, and then apply it to something else, another piece of paper (adding distortion) or even something like a piece of wood. Strange image manipulation--and 'analog'!--not some distortion effect done in your confuser with That Program That Shall Not Be Named!
The point being of course, that your comment about emulsion softening due to heat can be taken to the extreme of actually detaching the emulsion layer.
So prints are developed to completion when maximum black
Originally Posted by Doremus Scudder
has been reached and development noticeably slowed. Relying
on curves generated by Phil Davis that is not to completion.
Completion though is at maximum contrast; from those
curves 2 or 4 times the time to maximum black. He chose
twice the development times for the paper tests he was
conducting. With that much time they were "done".
Phil was in effect developing to maximum contrast.
More time he writes resulted in little increase. I take
it Phil's 'to completion' is maximum contrast or very
nearly. I believe that is a more true to completion
as further develpment generates no further
image. So to completion is to maximum
contrast. According to Phil. Dan