Date: Sat, 14 Dec 1996 13:59:23 -0500
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From: peter zimmerman <peterz@E....>
Subject: Re: 2-BATH DEVELOPER?
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Two bath developers have been around for a long time. the ACUFINE company
in this country markets DIAFINE, and Neofin markets EMOFIN, but not, I
think, in this country. See JOBO, the new importer.

Basically a 2-bath consists of a first bath which is a 'developer' slightly
acid balanced so it doesn't do anything, which soaks into the film in a
quantity controlled by the silver, grain size, emulsion thickness, and any
other appropriate variable. Bath 2 is not much more than Kodalk or some
other alkali accelerator which converts the developer stored in the film
into working developer. You'll see that with this kind of process most of
the variables between film types are compensated for by the differential
absorptions.

A 2-bath is almost always a compensating developer because there is the same
amount of developer in a well exposed region as in an unexposed region, and
it is absorbed into the emulsion and so not free to migrate much.
Consequently, the most heavily exposed regions cannot receive development to
completion, and the least well-exposed regions may overdevelop a bit. It
tames contrast well. ACUFINE and Neofine have advertised their products as
giving a one stop or two stop speed gain. I never saw that much when I
played with the stuff in the 1970s. Some two bath formulations yield very
fine grain, or are said to do so.

It is possible that the new one on the market is superior to the old ones
and worth using. For now, I prefer to push Minox films through soups I
understand.

pete z