From: Peter Marshall (petermarshall@cix.co.uk)
Date: 03/22/01-10:51:23 AM Z
> including, if I recall, that etch/bleach is a process done to a print
> between developer and fix - whereas mordancage is performed on fixed and
> washed prints.....
No, etch bleach can be done either way, so if Judy said so she was
correct. In fact when I did it we most often worked with fixed prints,
working away from the darkroom, as it gave us extra working space.
Presumably someone simply hadn't heard of it being done the other way. I
think the conclusion was that one was English and the other French,
although I'm not entirely sure this is the case.
The English edition of 'Photography - Theory & Practice' (602 in my
edition, p 387) is perhaps clearer than the French and the section quoted
is about dye-toning (and mordanting which is part of this) rather than
etch-bleaching an essential difference being in the removal of gelatin
during the etch-bleaching process. So if this is about mordancage they are
simply not the same thing.
>du mordançage etant le
>ferrocyanure d'argent
silver ferrocyanide is not involved in etch bleaching, but dye toning,
where it is acts as the mordant.
So whatever conclusion was reached last time appears to have been wrong.
To state it simply:
Mordancage is not etch bleaching.
Mordancage is dye toning
In Dye toning the silver image is converted into a mordant which then
fixes the dyes which are not otherwise retained in the gelatin. The silver
image can be bleached out after dyeing if necessary using a copper bleach.
In etch bleach, areas of gelatin are removed from the print and the
bleached silver image can either be fixed or redeveloped after this
treatment. The dyes used are absorbed by the gelatin rather than being
held in place by silver salts acting as mordants.
Of course you could do both things on the same print, as well as tinting
the paper base, and certainly some people who have worked in this kind of
area did combine various techniques.
Incidentally there are quite a few more sections in this book of alt photo
interest, including section 692 'dye prints by photo-mordants' as well as
all the normal alt processes. It used to be pretty common secondhand - I
have the 1937 second edition which is better than the first and was
reprinted at least 3 times.
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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