Here are some notes about my use of Jobo print tanks that new users might find useful.
I’ve been successfully processing RA4 prints in Jobo drums on a motorized roller base at 100º/38ºC for years. The key idea is to use this relatively high temperature so that the processing time is so short, that there in no significant temperature drop during the temperature-critical developing step.
I keep the solution bottles is a large dishwashing pan tempered to the processing temperature. After placing the exposed paper into the drum and securing the lid, I pour in a generous dose of water at approximately 105ºF/40.5ºC, let the drum spin for 15-20 seconds, dump the water and repeat.
Now the drum, lid and print are at least as warm as the 100ºF processing temperature. I set the timer for the developing step, dump out the water, pour in the correct dose of developer and let the drum spin for 60 seconds. In the meanwhile, I’ve poured a dose of tempered stop bath into a graduate. My stop bath is simply vinegar + water at about 1 + 5.
I prepare a dose of tempered blix, dump the water, pour in the blix, set the timer, and set the drum to spinning. Since the blix is acidic, as is the stop bath, there’s no need for a rinse between stop bath and blix. I dump the blix at the end of that process, and start rinsing with warmed water. I usually give my RA4 prints about 10 washes before removing them from the drum and drying.
In the above steps, only the developing step requires close control of the temperature. Since I prewarmed the tank and paper before introducing the 100ºF developer, I believe that it won’t experience any meaningful drop in temperature during the short 60-second developing step. The results I get making RA4 prints in this manner are identical to those I obtain using my CPP2 at 38ºC.
I use all of my RA4 solutions “one-shot” so there is no worry with cross contamination of chemicals. The resulting prints look identical to those I’ve gotten from commercial labs.
My reason for using the motorized roller base in the open air rather than the CPP2 is to preserve the Jobo for film developing, which requires longer developing cycles at elevated temperature. I bought the CPP2 in 1988 and want it to keep on working, as a replacement might be hard to find.
Here is the list of the Jobo 2800 series print drums.
https://www.manualslib.com/manual/1779771/Jobo-3012.html?page=12
There’s basically only two one-piece cylinder-and-base units: The 2820 Test drum that’s about 165 mm internal length and the 2830 with internal length 261.5 mm. Then there is the 2870 module, which is an extension cylinder—no bottom—with a cam-lock connection ring. It’s about the same length as the 2830 tank.
Jobo names the combinations with a unique 4-digit number that is printed on the upper section if it was sold in that particular combination.
I use the
2820 Test Drum for 1 or 2 prints of 4” x 5”, the
2830 for 1 or 2 prints of 8” x10”, the
2840 for a single 11” x 14” print, and the
2850 for a single 16” x 20” print.
Since I have the CPP2 with lift, I can use the 3063 for a single 20” x 24” print. The 3063 has a cog-drive lid only and no internal beaker, so it can only be used with large Jobo processor equipped with the cog drive and lift unit. It also requires the foot pump unit to pressurize the tank to pop off the lid at the end of the process.
The lids of the 2800 series tanks all have a beaker as part of the lid. That allows pouring in the solution with the tank standing upright (so long as you don’t put in more liquid than the beaker’s capacity). Then you turn the tank horizontal to pour the contents of the beaker into the tank as you begin rotation.