Mike
Your post as always thought-provoking.
> My feeling is that the evidence of history is against the Kallitype, but
> until someone with the facilities does some Arrhenius testing by
> accelerated ageing on known kallitypes, we can't be absolutely sure. Or,
> contrarywise, until someone comes up with some pristine ninety year old
> counter-examples that are demonstrably iron-based silver images. There is
> just a remote possibility that all the successful, unfaded examples of
> kallitype have been erroneously identified as platinotypes! Until then, I
> incline to the identification criterion - 'if it looks like a platinotype
> but is faded, then it's probably a kallitype'.
>
> Mike
Actually I think this last suggestion is a very real possibility, as my
experience from my own prints is that the only way I can reliably tell a
kallitype from a platinum/palladium print is by the writing on the back.
However as yet the oldest of mine is still less than ten years old. Some
have faded already in this time, others are going strong. Gold toning
doesn't seem to help much (again some have, some haven't.) Presumably the
gold only replaces some of the silver image. Would platinum toning do better?
I think it was a recommended method in some of the turn of the century
literature - and would make them even harder to tell apart.
Possibly the wide range of variations of the kallitype process makes any
generalisations about stability unreliable.
Just had a platinum, salt print, cyanotype sample put through an accelerated
light fading test by the way. The salt print got the highest 'blue wool'
rating for permanence of the three!
Peter Marshall
Family Album/Gay Pride - http://www.dragonfire.net/~gallery/index.html
Also on Fixing Shadows: ----------- http://fermi.clas.virginia.edu/~ds8s
Future Press and elsewhere... E-Mail: petermarshall@cix.compulink.co.uk