Originally Posted by srs5694
I'm not familiar with the specific "Larry of Main's" technique
you mention, but wouldn't the incorporated developer in most
modern papers contaminate the "A" bath, thus eliminating many
of the benefits of a two-bath developer? Of course, if you're
using a non-DI paper, this isn't an issue....
I think I'm the "Larry of Main"[sic] in the above contribution. The technique, about which I've written several times, is called divided development. It consisted of separating the developing agents from the activator (alkaline, e.g. carbonate) into two baths. In Bath A (developing ingredients, e.g. metol, hydroquinone, bromide), no visible image appears since there is no alkaline activator. Nor is it necessary to pay attention to time and temperature. Any time and just about any temperature will do. All that happens is that the latent image in the emulsion will absorb the necessary amount of developer to fully develop the image when it hits Bath B, the activator.
In Bath B, (no rinse between) the image fairly "pops" into view, and in a very short time, i.e. about 20 seconds is as fully developed as it will ever get. You can leave the paper in the tray as long as you want, but it will only ever develop until all the developer absorbed in Bath A is fully activated and then it stops.
This is a great technique when you live in an area where darkroom and water temperatures are hard to control. I stumbled on it in an old Dignan newsletter many years ago while living in the tropics and found myself frustrated by ambient water temps around 85F. It's also good, as I subsequently discovered, for controlling contrast, especially with graded papers. By having two trays of Bath A--one a "soft" formula such as Selectol (no HQ) and another "hard" or "normal" formula (e.g. D-72 or Ansco 125), I could arrive at intermediate contrast grades with graded papers. If I wanted a 1 1/2 grade, I ran a sheet of #2 paper through the soft Bath A and then into Bath B. If I wanted a 2 1/2 grade, I ran a #3 paper through the soft Bath A. Etc.
Through Ryuji's and others' comments, I've now become convinced that this two-bath technique is no longer necessary for multicontrast papers. So I'm back to a one-bath technique now, since virtually all my printing is on multicontrast. However, for graded papers or for locations where temps are hard to control, the two bath technique is great.
Larry
PS. Somewhere in the Articles or Chemistry recipes section, you'll find my longer article and some formulas for two-bath developers.