From: Peter Marshall (petermarshall@cix.co.uk)
Date: 03/12/01-07:31:23 AM Z
I have to admit that I have made kallitypes that have faded as well as
those that have not.
This is a topic that has been discussed at length before and people can
search the archive, so I will only make a couple of brief comments.
I think kallitypes made by the 'vandyke' method are probably pretty
stable, as also will be those made using acidic developers. Most people
seem to have concluded the fading occurs when prints contain residual
iron. Some of the traditional developers are alkaline and will lead to
iron being held in the print.
Platinum prints can be distinguished from kallitypes, so long as these
have not been platinum toned, by their catalytic action, for example
causing the breakdown of hydrogen peroxide. Platinum toned kallitypes will
give the same result, and more sophisticated methods are needed.
Distinguishing between a silver/platinum print (such as Satista) and a
platinum toned kallitype is probably impossible, but in the end who cares?
Peter Marshall
Photography Guide at About http://photography.about.com/
email: photography.guide@about.com
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Also on Fixing Shadows: http://www.people.virginia.edu/~ds8s
and elsewhere......
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