I'd like to try running B&W RC paper in the Jobo ATL
Considering the small volumes involved in Jobo rocessing, I'd look at simple one-shot development with Ilford Multigrade developer or similar.
For machine processing I have used ILFORD 2000 RT in the past, run through a Thermaphot 20" RT processor with good results.
2000 RT DEV
Liquid concentrate developer for high temperature machine processing of resin coated (RC) black & white photographic paper. Liquid concentrate print developer Economical and easy to use Produces superb quality prints High capacitywww.ilfordphoto.com
I'm not sure if paper process developers are 'too completion' or not.
Yes, in principle, they are. I say 'in principle' because of two reasons:
1: A pure 'to completion' process would theoretically give the same tonal scale and dmax even if the print is developed infinitely. Clearly, in reality, at some point the print starts to fog, so there's a limit to how far you can take this.
2: There may/will be subtle differences in tonal rendering between two prints that are both developed 'long enough', but one being developed significantly longer than another. If these differences are meaningful enough to worry about, I leave up to you to decide.
Personally I'd be inclined to keep it as simple as possible and determine a minimum development time for which additional development gives to appreciable change in print densities, and a maximum development time that does not yet result in fogging or meaningful changes in the h/d curve. Then you have a window you could stay in without having to worry too much about very subtle differences within that window.
Is there a minimum development time test?
Ilford says the minimum developing time for Multigrade RC paper is 45 seconds, using Multigrade developer diluted 1+9. They have a chart of machine development times and temperatures on page 3: https://www.ilfordphoto.com/amfile/file/download/file/1826/product/1696/
I'd expose some step wedges and develop them for increasing amounts of time. Compare them (visually, or by measurement) and note the shortest time that gives full development and after which no change occurs. Not sure if it's documented somewhere; I'm sure it must be, but it's quite straightforward I think.
Unfortunately MG is not as long lasting as I need it to be. One of the benefits of Eco is that it lasts I think like 8 months when kept in full bottles.
The term full development is misleading, it should be the minimum time to reach Dmax plus around another 10 to 20% safety factor. The problem is extending development longer shifts the mid tones and blocks up the shadow details.
I mix my own PQ print developers based on Ilford published formulae using Phenidone, however to commercial strength, using Potassium Carbonate and Hydroxide instead of Sodium Carbonate. I find the shelf life is a lot better even in partially filled bottles than the reformulated Ilford Dimezone versions. I'm talking about over a year in partially filled bottles..
You need a developer like 2000 RT because it's specifically designed for self replenishment in an RT machine, I'm sure other developers would work initially, but you run the risk of much earlier collapse with some formulae, making them significantly less economic.
Ian
I'd expose some step wedges and develop them for increasing amounts of time. Compare them (visually, or by measurement) and note the shortest time that gives full development and after which no change occurs. Not sure if it's documented somewhere; I'm sure it must be, but it's quite straightforward I think.
I forgot to update this thread, totally spaced. I'm going to stick with RA4 in the Colex and try to do RC B&W processing in the Jobo ATL 2500. That's why I'm considering Eco 4812. It'll do a lot of sheets and lasts for months. If I keep 5L in the self re-filling system and track the sheets it could be pretty efficient. I'm just not sure what time and temp to use. The Jobo can do around 21-24C with no problem. Might have a hard time maintaining 20C in the warmer months.
I forgot to update this thread, totally spaced. I'm going to stick with RA4 in the Colex and try to do RC B&W processing in the Jobo ATL 2500. That's why I'm considering Eco 4812. It'll do a lot of sheets and lasts for months. If I keep 5L in the self re-filling system and track the sheets it could be pretty efficient. I'm just not sure what time and temp to use. The Jobo can do around 21-24C with no problem. Might have a hard time maintaining 20C in the warmer months.
Thought I'd clarify why the ATL is not commercially viable for B&W RC prints, the time loading it the process cycle, uneconomic in terms of chemistry, the cleaning/drying etc. Fantastic for film processing, or for colour prints.
The Colex is as you've decided better for your colour print processing, if you ultimately want an RT machine for B&W there are simpler/cheaper options. One advantage of dish processing is it is cheap, you can process a few prints in a tray at the same time. A print dryer might be useful.
Ian
Oh I'm not so sure still. Certainly 8x10s are easy to crank out in trays but 16x20s and 20x24s could hold some advantages with rotary. I think chemical usage would in fact be more economical because I can just pour the 'just used' solution back into the working bottle and go on. Plus the ATL 2500 has floating lids in the re-fill tanks and the tempered bottles are pretty full at all times. At the very least I'll try it out.
For dryer, I have an Arkay RC 2100. As I get older, and I'm not that old, time is so much more important to me so I've set up efficiencies where I can.
Photographes
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If you have lots of money and are processing murals these are amazing
Biggest I'd go is 20x24. After that chemical processing gets crazy. That's what inkjet is for!
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