[pure-silver] Re: Developing Portra and Kodachrome in B+W chemistry
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <pure-silver@xxxxxxxxxxxxx>
- Date: Sat, 31 Mar 2012 16:30:27 -0700
----- Original Message -----
From: "Bogdan Karasek" <BKarasek@xxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Saturday, March 31, 2012 2:49 PM
Subject: [pure-silver] Developing Portra and Kodachrome in
B+W chemistry
Hello,
I was doing inventory in my freezer and found a 35mm roll
of Kodachrome 64. I keep fantasizing this is the last
roll of Kodachrome left in the world. But I am sure
there are others who still have KC hidden in the deep
recesses of a fridge somewhere. Be that as it may, I read
in passing, on Apug, I think, that KC can be developed in
B+W chemistry. Any truth to the idea, and if so, what
would be the best brew?
Last week, I was also given 4 4x5 sheet film holders
loaded with Porta 100. I'm not into colour but B+W.
Anyway, can the Portra also be done in B+W chemistry? By
the way, the holders were accompanied by a Graphic View I
in its case and an Ektar 203/7.7 lens mounted on the lens
board.
Cheers,
Bogdan
The Graphic View I is a decent little camera. The main
difference between it and the later II is having base rather
than center tilts and I think the II has longer bellows
draw. The Ektar 203mm, f/7.7 is an excellent lens of the
dyalite type similar in construction to the Goerz Dogmar. It
is the only one of the old 70 series Kodak Anastigmats to be
continued. The difference between it and the No.70 K.A. is
that its coated. It has excellent color correction. It was
curiously enough an economy model where one wanted a good
performing lens cheaper than the 8-1.2", f/6.3 Commercial
Ektar.
Kodachrome film is essentially B&W film and will
develop in something like D-76. However, it has a yellow
filter layer which is made of colloidal silver. This is
normally bleached out when the silver image is bleached out
after the final reversal development. It can not be bleached
out without also bleaching the image. I think any toner
which would protect the silver image from bleach would also
tone the filter layer. You could get around this by making
dupe negatives on panchromatic film. When panchromatic B&W
paper was available it worked perfectly for color films
despite the dye images and would have worked OK for
Kodachrome as B&W. It is just possible that because the
silver in the filter layer is so fine that a very mild
bleach such as film strength rapid fixer with about 15 grams
per liter of citric acid added would bleach it without
affecting the silver image too much. One would have to
experiment. This is an effective bleach for dichroic fog,
which is also colloidal silver although on the surface of
the film rather than under an image layer as is the filter
in Kodachrome.
Kodak Portra is a color negative film. All modern color
negative films have a built-in color correction system based
on self masking using colored couplers. This accounts for
the amber overall color the film has. In fact, its not
overall and if one looks at the image closely one can see
the amber is not there in some parts. The color comes from
the coupler, or dye intermediate, that is, the substance
which becomes dye during development. A Kodak researcher
(name gone but will come back as soon as I send this) found
that if the coupler was made in a color that absorbed the
unwanted transmission of the dye but changed color as it
became dye, an automatic mask would be produced to correct
the color. There are masks in to layers of negative film
and together, when the coupler is undeveloped as in a clear
area of the film, the produce the familiar amber color.
Since this is a dye it can be bleached out where the image
is silver but I have forgotten which bleach will destroy it
without also removing the silver image. I suspect a
permanganate stain remover may work. In any case, even if
the silver image is bleached it can be re-developed.
Since Portra is currently in production and processing
is still available I wonder about the utility of processing
it to B&W.
--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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