Kevin O'Brien (kob@paradise.net.nz)
Sat, 20 Mar 1999 08:17:59 +1300
I suspect the problem is more complex and may be a combination of silver
density and exposure.
When I was making iron-silver prints I was only using 25g silver nitrate to
900ml of coating solution. That's about 1/3 of the silver being used in some
current formulations and the coating was only onthe surface. The results
were suffciently impressive to make paper negatives. The darks were
beautifully deep and no chemical contrast agents were needed.
The surface and coating thickness were important. Less absorbsent surfaces
gave a greater contrast range. What's been described as 'butcher's paper',
or household lunchwrap, as was a well sized, calendared, water colour paper
gave excellent results. I worked from the premise that the coating should be
on the surface - how else is it to be exposed ? The development is physical
and as it occurs prevents the lower layers from being similarly acted on.
Probably for that reason, a double coating reduced the contrast
substantially as did unsized etching papers.
The coating was put on under a red safelight with a cheap, very soft, wide,
short-haired, watercolour brush. The brush was wetted first. It was done
both ways for eveness.
The process was fussy about exposure. Too much reduced contrast and beyond
that gave obvious solarisation. Correct exposure was where the darks in the
negative were just showing as pink, or just about too, in the print with
maximum brown in the margins. Printing out was by sunlight. A UV lamp took
longer and gave a more sepia colour. It was easy to get used to the look of
a print that was 'done'. Once that occurred it had to be covered.
Kevin O'Brien
-----Original Message-----
From: Richard Sullivan <richsul@earthlink.net>
To: alt-photo-process-l@skyway.usask.ca
<alt-photo-process-l@skyway.usask.ca>
Date: Saturday, 20 March 1999 05:29
Subject: Re: Kallitype image invertion
>Most solarization and bronzing in colloidal silver prints like Kallitype
>and Van Dyke is caused by coating too thin, too much on the surface,A while
>back or too little metal in the emulsion. Carlos Gasperinho was working on
>improving the Kallitype process. One of his ideas was to overload the
>silver nitrate way beyond what most formulas call for. He said this cuts
>down on solarization and bleach back during fixation. In a three way
>conversation with myself, Carlos and Mike Ware, Ware said it sounded quite
>reasonable.
>
>--Dick Sullivan
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