Richard Knoppow (dickburk@ix.netcom.com)
Thu, 28 Oct 1999 17:07:56 -0700
At 05:47 PM 10/28/1999 -0400, you wrote:
>Some time ago, there was a discussion on Ilford ID-11 plus. Here's the
>information I just received from Ilford. Interesting. So now we know.
>**************************************************************************
>Cinnamic acid disulfide is a silver sequestering agent which helped to keep
>silver in solution. It was added to help reduce the re-depositing of silver
>into the film emulsion. The result was reduced overall fog levels, produced
>cleaner, brighter looking negatives.
>ILFORD ID 11 Plus was discontinued about 4 years ago because it was found
>that Cinnamic acid disulfide appeared to reduce the film speed of some new
>technology films.
>*****************************************************************************
>
>
>Sil Horwitz, FPSA
>Technical Editor, PSA Journal
>silh@earthlink.net
>Visit http://www.psa-photo.org/
>Personal page: http://home.earthlink.net/~silh/
>
Thank you so much Sil. I was the one who brought up the question. I had a
suspicion this was the purpose of the cinnamic acid. D-76 and other high
sulfite developers, as you undoubtedly know, works partially by physical
development. i.e. the developer dissolves some silver halide from the
emulsion and re-deposits it on the image as metallic silver. Part of the
low-grain characteristic is supposedly due to this effect. Unused D-76 has
a fairly high fog level. Some alternative formulas, like Agfa's old one,
add a small amount of bromide to control this. In the paper describing the
buffered version of D-76 the authors mention trying a variation with some
bromide. It resulted in a very slight increase in film speed due to
suppression of fog but they did not find it useful enough to add to the
formula. D-76 was intended originally for developing motion picture
negative so it would have acquired bromide rather quickly in use.
"Some Properties of Find-Grain Developers for Motion Picture Film" H.C.
Carlton and J.I. Crabtree (Kodak Laboratorys), _Transactions of the Society
of Motion Picture Engineers_ Vol. XIII, No.38, 1929 p.407
The above discusses about every variation of the D-76 formula possible.
There is a second interesting article in the same issue:
"Borax Developer Characteristics" H.W.Moyse and D.R.White (DuPont Redpath
laboratories) ibid. p445
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
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