When developing film or paper in black and white photography, only three variables are important. Time, Temperature, and Agitation.
Without a processor, development time is calculated based in the room temperature, as usually is published on brochures that comes with the films/papers.
In B/W film, any increase in temperature will result in a decrease in developing time, and vice-versa. Within limits, of course!
After read a lot of articles published in the web by professional, decided try the developing process in a JOBO system. Due to budget restrictions, I choose a used JOBO CPE2 first generation at sale in the web in a very good condition.
The CPE-2 Processor only controls agitation and bath temperature. Time is controlled by the manually chemicals fill and drain, usually executed by deploying the chemicals and operating the lift at the end of each scheduled time for each chemical or washing water cycle.
So, you will need a manual darkroom timer (I personally use the Iphone Develop! App – See this Link). But you can also use a normal chronograph watch or timer… Paterson have some very useful models.
For developing times, you can checkout the gorgeous database film developing info at Massive Dev Chart site – See this See this link. There is also a iPhone App.
The CPE2 processor uses a water bath to ensure even tempering of the chemicals, including the tank and drum that contains the exposed paper/film (JOBO 2520 drum for two 35mm film spirals, JOBO 2840 model for 11×14″ papers.
For Black&White development with developing temperatures around the 20° Celsius, countries where air temperature is usually lower than 20 degrees celsius, the temperature warming coil do a very well the job in warming the water until the desired temperature. But in countries where air temperature is above 20 degrees celsius (like mine!) the water tank must be filled initially with cold water (lower than 20 degrees celsius) and wait until the CPE2 coil warms the bath together with the chemicals containers and bottles (see upper figure) unail it reach the desired temperature. This allows the bath to reach 20 degrees even when the air temperature is higher, just by few moments where the development must start immediately. I use a 10 liter canister in the refrigerator to fill the tank bath.
Is very advisable to use an accurate thermometer to control the rise or fall of the temperature of the bath.
The JOBO CPE2 allows you to achieve more consistency, roll by roll, and easily have the repeatability of all the developing processes with no errors.
No need to install the CPE2 in a darkroom, because the developing tank is light-proof during the developing operation. But the film must be inserted in the developing tank spirals in complete darkness before the development process – I personally use a special light-proof bag with double zips. Plenty of model at sale in eBay!
The CPE2 uses a bi-directional rotation system to agitate the solution. It’s very important that the rotation be bi-directional because it prevents the chemicals form flow patterns in the films being developed, resulting in bad developing film/paper. It also allows a decrease in the developing process time to do not over-developed negatives (I usually use 85% of manual equivalent process times).
Also, an increase in temperature causes over-development – this is why is important check air temperature to control the evolution of the water bath warming.
The JOBO CPE2 is a great tool, and with the lift, no need to worry about chemical spills around the room and the strong odors they leave. The processes are completely controllable and clean, and the lift operation is a must, because you only need to worry about filling or draining the chemicals or water into and out it, in a very clean fashion, leaving you fully concentrated in the developing times.
More info about this will be published.
An article about the steps I did to repair the lift leaks of chemicals into the bath during the processing, the lubrication of the lift and the motor gears, and some electronic repairs, due to the age of the equipment (more than 30 years!!!).
Note: You can see a JOBO CPE2 in a B&W processing action in Tim Layton’s YouTube video here!