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

Hi all,
First of all, thank you Michael for the link to the book in question.
Unfortunately it was not very readable. It seems a lot of formatting as
well as some tables and figures have gone missing in this archived
version. Some of the info is still readable, though.

Ryuji,--
I would very much like any details you can provide. I'm not sure if this
should be done on the list, but I'm posting this, so that others can
express their interest (or lack of such). If no one is interested, then
maybe we should continue off list.
(I will be off line for several days at a time in the near future, so
please don't give up on me if I do not respond immediately).

This is my situation:

- I'm fairly skilled in basic chemical methodology, and have a
reasonably complete, but simple laboratory (I run a small microscopy
lab). As long as things are not too expensive, I am prepared to add to
my equipment to enable small scale emulsion making and coating.

- I have basic knowledge of how emulsions are made, and their major
components.

- I have a wish to be able to make glass plates for taking B&H large
format pictures. This is partly founded in basic curiosity, and partly
in the wish to be self sufficient if the day comes when film is
unavailable, or too expensive for me to use (this day seems to approach
more rapidly than I would have imagined just a year ago). Furthermore, I
would like to use some slightly odd formats with home-built cameras, and
using home made glass plates seems like a sensible way to do that.

- I don't care too much about film speed (OK, it would be good with a
little more than ISO 1.5). If I need speed, I shoot digitally, or with
colour slide film while it lasts.

- I do care about image gradation. On the other hand, I will probably
not be enlarging too much, so small imperfections should not present too
much of a problem.

- I prefer a small grain film, but can easily think of situations where
that might not be important.

- If it is possible, I do prefer a low-fog film, since I would like to
attempt reversal processing.

- Any chromatic sensitivity is of interest, in the following order:
Panchromatic (preferred, but I realize it has severe complications in
production) > ortho-panchromatic > IR-sensitive (this would be great,
but no substitute for a visible range film)> orthochromatic > blue
sensitive.

- I'm in no rush. Before I even try to make an emulsion, I would like to
know more about what I'm getting into. If I am ready to make my first
plate a year from now, I will label it success!

- If I do eventually decide to try this, I would prefer to be able to
make at least 10 11x14 or 20 8x10 plates at one time, preferably more. I
  will probably not be able to make plates more than a few times a year.
My ideal situation would be to arrive at an acceptable process, and
within a reasonable time-frame make enough for a years photography (I
already store film and paper in a freezer).

This I don't have:
- Detailed knowledge of the chemistry of sensitation (I know a fair bit
about dyes, but not related to emulsions)

- ANY recipes whatsoever (consequently, anything you are willing to
share from your notebook is very welcome).

- _Practical_ knowledge on how to make the emulsions (i.e. exactly what
equipment is needed, temperatures and times for nucleation etc etc.)

- Practical knowledge on coating. This is only partly true, since I've
done a fair bit of cyano, van dyke and a little bit of gum-dichromate. I
have no idea what it takes to produce an even gelatin film on glass,
though. I read some holography links that seemed interesting, but I'm
unsure if those films will be applicable to general photography. Several
seemed to use a simple "pour on" coating technique. If it is good enough
for holography, it may be good enough for general imaging as well I
suppose. I also don't know if I need to order glass larger than my
end-format, and cut it to size after coating. Possibly coating 20x24, to
cut it down would save a lot of work?

- You ask what kind of setup I'm willing to use. Well,- I'm not ready to
answer that. Possibly you can make a recommendation based on the
information I've given above, or guide me to literature to read up on.

- When you talk about jets, I have no idea whether you are talking about
some special coating equipment or simply three burettes to supply
different solutions during emulsion mixing. Quite possibly you are
talking about something different all together....:-)

Finally; I have no way of getting hold of the papers you mention. Could
I ask you to send a copy? I'll of course pay for copying/shipping.

Ryuji Suzuki wrote:
> 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 Sat Oct 22 16:05:07 2005