Re: toning VDB & kalli - 2 questions

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From: Judy Seigel (jseigel@panix.com)
Date: 12/02/02-02:04:54 PM Z


On Mon, 25 Nov 2002 rurmonas@senet.com.au wrote:
> Judy,
>
> I may be wrong here, but my undestanding of VDB was that the thiosulphate
> bath was not a fixing bath, but a simple way of providing sulphur to react
> with the silver. As the silver is much finer than a silver bromide paper,
> the conversion of silver to silver sulphide takes place. This is the same
> as sepia toning and so the resulting print should be quite stable. I would
> expect Kallitype to be similar.
>
> > What about toning after fixing? Is that effective? It might also alter
> > the color, but then it might not.
>
> If my comments above are correct, then toning after the thiosulphate bath
> would need something that will react with silver sulphide, as well as
> any silver remaining in the print. Thus not all toning baths would be
> suitable.
>
> Perhaps someone will confirm / deny my understanding.

This theory of VDB fixing is one I've never heard -- tho fascinating...
I was hoping someone would have further info or input. How could that be
tested? When my students loved the color of pre-fixed VDB & wanted to
leave print that way, we tested by doubling exposure to unfixed but washed
print -- there was very little change, although the print was overall
flatter than if fixed.

Though what that means re Richard's suggestion I have no idea. I do know
that long fixing (more than a minute in my tests) of VDB starts to bleach
it out, and will ultimately bleach it a lot. What would that say about
whether it is making the silver compound soluble or just sulfiding?

Any chemists listening? any way to test?

Judy


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