Hello Uwe,
Tetenal wrote the following on this subject around 1960:
If the aim is to produce enlargements from hard negatives that reproduce highlights and shadows satisfactorily – a goal that is usually unattainable with standard single-bath development – then we recommend two-bath development using Centrabrom and Eukobrom.
[...] the principle is to first conduct the development of all the details onto the paper in very smooth gradations using a very gentle developer, and then to provide the necessary contrast using a brilliant developer, without the shadows ‘closing in’ or the highlights ‘becoming blocked’.
This can be achieved as follows: perform dilution of Centrabrom with 1–3 parts water, then develop the ‘correctly’ exposed paper in this solution until the highlights just begin to appear, and then enhance the image through further development in Eukobrom until the desired coverage and brilliance are achieved. The reverse approach is also viable, i.e. initial development in Eukobrom followed by final development in Centrabrom. We find the first method more effective.
The most extreme contrasts can be overcome by using Neofin Blaue for the initial development (1 vial or 30 cc diluted to 400 cc); a process that is somewhat costly, but entirely justified in extreme cases. In this ‘softest developer in the world’, so to speak, only a faint outline of the image appears in all its details, which is then carefully enhanced in Eukobrom.
(Dokumol did not yet exist at that time.)
In 1982, Tetenal wrote, in a text otherwise similar:
The order of development always proceeds from the soft to the hard developer. As PE papers may already contain developer substances in the emulsion, the paper must be pre-soaked before being processed in the first developer.
Warm regards from Westphalia
Henning
