rurmonas@senet.com.au
Date: 12/06/02-05:51:14 AM Z
Quoting Liam Lawless <liam.lawless@blueyonder.co.uk>:
> That the image "pops" in hypo is I think explained by the fact that it makes
> the iron soluble. KOL describes one of Herschel's discoveries: "that on
> exposure to light ferric salts become reduced to the ferrous state, and that
> the ferrous salts so produced can combine with or in turn reduce other salts
> to create an image."
I differ here. There are several FAC based processes which develop
in water. This suggests that the ferrous component of exposed FAC is
soluble in water. Hypo is however a silver solvent, so there may
still be some validity to your argument.
> did
> anyone ever try putting a cyanotype straight into hypo, and if so, what
> happened?
A washed cyano. Fixer has no effect (I was experimenting with clearing
paper staining). I have not tried the effect with an unwashed cyano.
I suspect it will develop normally with perhaps some change in tone
due to addition of other chemicals into the prussian blue structure.
> My belief, then, is that hypo is both developer and fixer for VDB, and that
> the image substance is predominantly silver. Because the silver particles
> are very fine, I expect that a small amount of sulphiding takes place, but
> not much. VDB silver(?) responds to gold toning in much the same way as the
> silver of a chlorobromidebromide print, not in the way that silver sulphide
> does on sepia toned prints. And last night a sepia toning solution produced
> visible change in a VDB print, which I would not expect it to do if the
> image was of silver sulphide already.
However thiourea toner (without bleach) should have minimal reaction
with metallic silver (which is why normally we use a bleaching step).
Of course the fine size of the silver could allow more reaction to take
place. I suspect there is a more to this than a simple silver or silver
sulphide issue.
Richard
--- Richard Urmonas rurmonas@senet.com.au ------------------------------------------------- This mail sent through SE Net Webmail http://webmail.senet.com.au
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