From: Peter Marshall (petermarshall@cix.co.uk)
Date: 07/09/01-12:23:46 PM Z
> I also happen to like the rusty colour of untoned salt prints.  Being 
> archival is, of course a matter of degree.  Frankly, I do not know 
> how unstable untoned salt prints really are.  From the fact that 
> virtually all known salt prints of the classical period are toned one 
> should by no means infer that the reason for toning was to achieve 
> greater permanence.  I have a sizeable collection of pre 20s 
> photographic literature.  The authors when giving recipes for toning 
> _never_ discuss archival matters but only image colour.
 
Just been catching up on the list.
Both the London Photographic Society and the French Association set up 
committees to study the problem of fading around 1850 - so they were very 
much concerned with print life at this time. All of the prints from 
Talbot's Reading works show at least some fading now, and I think plenty 
did by 1850. It was something that was impossible to ignore at the time. 
The French put up a large prize - from memory 100,000 francs - for 
solutions to fading.
Some of the recommendations concerned better washing of prints, but gold 
toning was also recognised as giving greater stability. It was the 
concerns over fading of prints that led to the great interest in 
bichromate processes that eventually led to the carbon print and the 
collotype (as well as other processes). I have a feature which includes 
something on this coming out next week on 'About Photography'.
My untoned salt prints still look as good as the toned ones over 10 years 
later, so they are not spectacularly unstable. On some papers the colour 
shift is not too great (if I haven't written on the back I can't always 
tell if I gold toned a print.) The colour also depends on the particular 
salting solution of course.
Peter Marshall
petermarshall@cix.co.uk     +44 (0)1784 456474
31 Budebury Rd, STAINES, Middx, TW18 2AZ, UK
_________________________________________________________________
London's Industrial Heritage: http://petermarshallphotos.co.uk/
The Buildings of London etc:  http://londonphotographs.co.uk/
Also on Fixing Shadows:       http://www.people.virginia.edu/~ds8s
and elsewhere......
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