I sincerely hope you have figured out your developing issue. As I stated before, I know how frustrating those can be, which is why I took an interest in and replied to your public post looking for input on the matter.
Any advice I've given has been based not only on readings but on my experience developing hundreds of rolls and hundreds of sheets of film using stand and semi-stand methods. I know others here who have contributed to this thread have far more real world experience than that.
Best of luck.
What I have experienced so far doing stand development with Rodinal/R09, is that the only thing (more or less) that seems to matter is in fact the temperature.... In your case I'd give all I can to stick to 20° max 21° C from now on.
A bit of theory here.
Without agitation the developing agents in the film and just outside the film (about 0.1mm, IIRC) becomes used up. That 0.1mm acts as a barrier keeping fresh developing agents from entering the emulsion. So development stops at that point. Past that point very little goes on, you can actually leave the film setting there for several hours with very little increase in density.
Now with increased temperatures, within limits, what happens is the developing agents are used up faster, so developing ends sooner. Those limits, IIRC, are from 60F to 85F. At higher temps Brownian motion starts providing self-agitation.
I have let film set for over two hours with no noticeable increase in density, I have not tried to see how soon I could pull it, but I would guess at a point only slightly longer than it takes to process the film by time and temperature with normal agitation at that dilution.
As I have said, I have been using this method for a couple of years, and except for the last two batches (of of one roll of 120, and the other of two rolls of 120), all those negatives are about the same density. All at room temperature with no adjustment for seasonal changes. So, I concluded that something has changed without my being aware of it, and came here where I felt the experts were for help. What I get is told that two years of experience is wrong.
Now, I have read a lot about stand developing on the web, and in almost every case I noticed that the person trying it could not believe it did not need additional agitation, so did not actually use stand developing. The few that did not do additional agitation reported the same results I have had. Once you get into having to do temperature control outside of broad limits, stand development loses all of its advantages, and you might as well go back to time and temperature. Which all those saying I do not know what I am talking about, seem to have done.
For those who have to know the details: I mix Rodinol 600ml + 6ml. 600ml water stop. 540ml + 60ml fix. All dumped after one use. I then do a modified Ilford wash. To insure consistency I agitate each with 5 slow inversions, then set until the time is up. The only thing that is at all critical in this system is agitation, which is why I chose to use the same agitation for all cycles. If I do it the same for everything, I will not forget and do it wrong for the critical developer stage (I have a neurological problem, that I translate what the doctors are saying as, "Duh, I do'no", complicated by a-fib & a nasty form of sleep apnea, which makes life interesting. Read interesting as meaning it make it very hard to get up and get started at anything. Strangely, once started you only seem to have a sight handicap, in that you run out of steam in a couple of hours, and are somewhat absent minded.)
For anyone reading this thread, wondering about stand development, don't take anyone's word for it, try it yourself. The simple fact is that we can all be right, slight changes in the system can account for the differences mentioned here.
So Tom, should we apologize for trying to help out? I don't think that anybody has been disrespectful, or trying to 'prove you wrong'. Just trying to add from their own experience.
There are a few factors that affect film developing:
1. Developer dilution
5. To some extent water quality (regional differences can be pretty large)
You have time, agitation, dilution, and water quality under control. Process of elimination leaves temperature. Until you contributed the idea of 'environmental agitation' caused by an external factor. Agitation is indeed a factor that contributes to development, so that is absolutely a card to play.
But, and this is where I think most of us get hung up - when you try to troubleshoot a developing problem, you eliminate as many variables as possible. An easy target is temperature. I mean, what else in your developing system is a variable?
So, it could very well be that all of us that have replied don't know enough about film developing theory and practice to actually solve your problem.
Finally, my own experience with Rodinal is that it doesn't exhaust easily. I've had it happen at 1+200 dilution (2.5ml concentrate), but not at 1+100 (5ml concentrate). I've used standing development a fair bit (agitating only at the beginning), processing both 35mm and 120 film a lot using this technique, and my own findings indicate a result different to yours - time does matter. I've processed rolls for 40 minutes, 60 minutes, and 90 minutes - with different results at 1+100 dilution. And I used 5ml of concentrate to 500ml of water. That's even less concentrate than what you used. Go figure!
Rest assured that I am not trying to contradict you - I am only trying to contribute my experience in hope that you might benefit from it in solving your problem. Good luck. I hope you get it figured out.
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- Yousuf Karsh
"We are what we repeatedly do. Excellence, then, is not an act, but a habit".