RE: Silver chloride contact printing papers - not AZO

> Judy wrote:
>
> I'll add, though that DOP can be made into POP with a chloride bleach...
> I think Chris Anderson, or maybe it was Liam, or both(?) have done that
> too... You bleach it back with hydrochloric acid & (as I recall) a
> bichromate bleach... and just leave it in the sun or strong light and
> forget about it... You think nothing is happening, but in a few days you
> have a brown tone quite tactile photograph. Could probaably gold tone it
> too, if you felt the urge.
>
>
> Richard Knoppow wrote:
>
> Somewhere, in the all too distant past, I also had
> instructions for making POP out of DOP. Mainly I remember
> that it was treated in a solution that included silver
> nitrate. I can no longer remember where I saw this but have
> a vague clue that I can follow up.
>
>
> Liam quoted L.C. Clerc and elaborated:
>
> 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.

Maybe the Clerc recipe is a typo. Think albumen. I have had acceptable to
good results using AgNO3 solutions in the 5% range, usually with a bit of
citric, tartaric, or acetic acid. Float the paper (emulsion down, for
those of you not familiar with salted paper or albumen), don't immerse it.
Make sure you use "real" DOP, not the developer-incorporated stuff that so
often passes for photo paper these days. I've used Kodabromide (sadly,
discontinued) and Azo successfully this way.

Best regards,

etienne
Received on Wed Jan 28 20:59:56 2004