Re: Silver chloride contact printing papers - not AZO

----- Original Message -----
From: "Liam Lawless" <liam.lawless@blueyonder.co.uk>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, January 28, 2004 5:56 PM
Subject: RE: Silver chloride contact printing papers - not
AZO

> Richard,
>
> One place that has instructions is Clerc, who says:
>
> "Gelatino-bromide or gelatino-chloride development papers,
which, for
> one reason or another, have become unsuitable for their
proper purpose,
> may be converted into print-out papers by soaking them in
a weak
> solution of silver nitrate (about 0.5 oer cent) or in a
solution of a
> reducing substance such as sodium or potassium nitrite
(about 5 per
> cent), salts of hydrazine, various developers, sodium
sulphite, stannous
> chloride, etc.
>
> "After soaking for some minutes, the paper is placed to
dry in the dark
> without any preliminary washing. The same treatment can
be applied to
> negative plates or films.
>
> "The method of using is the same as for gelatine print-out
papers."
>
>
> Well, I tried once with 0.5% silver nitrate and (probably)
a
> chlorobromide paper. As I recall, the silver bath had no
effect at all,
> compared with an untreated sheet. As I understand these
things, the
> free silver nitrate permits much greater image densities
from printing
> out, by combining with the halogen liberated by light
exposure of the
> original silver halides to form more silver chloride or
bromide as
> printing proceeds. I'd hazard a guess that the problem is
that the
> original silver salts of the development paper just aren't
sensitive
> enough to UV, their speed in this respect (I guess) having
been
> determined by the emulsification process. Maybe
develop-out papers were
> different in Clerc's day, but it might be interesting for
someone with
> time on his (her?) hands to try again with a developer.
>
>
>
> Liam
>
    Thanks Liam, I am pretty sure this is what I was
thinking of. Perhaps it doesn't work because the materials
have changed or perhaps it never worked. One would need both
a lot of time and a lot of Silver Nitrate.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com