Re: Bromo-iodide Silver Gelatin Emulsion as an Alternative process.

I don't have time to answer the question today, but the book in
question is pretty bad. I have Wall's book and Baker's second edition,
both pretty bad. Indeed, books on emulsions are generally pretty
bad. And good books talk about physics and chemistry of emulsion but
they won't go into how to make emulsions, as they assume that the
readers know it.

I can find formulae for plate emulsions from my notebook if you tell
me the speed you are looking for, and the kind of setup you are
willing to use, etc.

It's possible to make a fairly fast emulsion of good gradation and low
fog, but it involves a minimum of triple jet setup (one jet each for
silver, bromide, iodide), change of temperature after nucleation,
sulfur+gold sensitization, etc. And two or three batches of emulsion
should be made for blending to increase latitude.

On the other hand, formulae that use single jet are easier to follow
but they are usually slow, coarse emulsion of nonuniform grain size,
with lots of dead (junk) grains that do not contribute to sensitivity
or image. This type of emulsion phased out from market in mid
1980s. But you can still make a pretty usable emulsion by this
approach.

Examples of the former type emulsions appear in relevant patents but
those are usually not ready for amateurs to follow (formulae don't
include all necessary details). There are some good examples of the
latter type emulsions. See Carroll's paper in J. Chem. Education,
dated c. 1930. I mentioned this paper a few times in the past, so it
should be easy to search. Hill also published another paper in the
same journal c. 1960. These are better starter materials than any book
I know of.

Ryuji
Received on Thu Oct 20 21:43:36 2005