From: Sandy King (sanking@clemson.edu)
Date: 01/25/02-01:41:10 PM Z
Peter Marshall wrote:
And if you tone the kallitype with platinum it will become even more
difficult to tell the difference between the two! In fact, I
understand that a very expensive testing procedure would be needed to
distinguish between a full-bloom platinum and a platinum-toned
kallitype.
I platinum tone all of my kallitypes, not to fool anybody but because
I think it greatly adds to their permanence. What I do is develop the
kallitype in a 20% sodium citrate developer, which gives a warm brown
image, then tone with the formula Dick gave yesterday (5 g of citric
acid per liter of water, plus 5ml of platinum #3 solution). This is
done after clearing but before fixing. Toning is usually a subtle
process but with this developer/toner combination the result is quite
dramatic as the brown image rapidly turns to a neutral black on
contact with the toner. Less rapidly of course as the toner depletes.
As for image permanence, which has always been an issue with the
kallitype, one could make a good case that a well-processed
kallitype, platinum toned, is as permanent, if not more so, than any
other type of silver image. The keys to permanence would seem to be,
1) complete removal via clearing of unused iron, 2) proper fixing of
the image to remove the unused silver, and 3) complete removal of the
hypo via adequate washing, or its conversion through the use of a
hypo eliminator which allows a shorter final wash.
Sandy King
>
>I've made prints from the same neg and the only way I could tell which
>was Pt/Pd and which Kallitype was by looking on the writing on the back. I
>was using a developing out method with both processes, and there were no
>significant differences in tonality/tonal range.
>
>We have speculated in the past that some 'platinum' prints in collections
>may actually be kallitypes. There were several formulae published around
>1900 which claimed to produce kallitypes which looked identical to
>platinum.
>
>Peter Marshall
>Photography Guide at About http://photography.about.com/
>email: photography.guide@about.com
>_________________________________________________________________
>My London Diary http://mylondondiary.co.uk/
>London's Industrial Heritage: http://petermarshallphotos.co.uk/
>The Buildings of London etc: http://londonphotographs.co.uk/
>and elsewhere......
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