Re: APIS, hydroquinone hardening

----- Original Message -----
From: "Ryuji Suzuki" <rs@silvergrain.org>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, July 15, 2005 9:38 AM
Subject: Re: APIS, hydroquinone hardening

> I don't think crosslinking mechanism of chromium is disputed.

Nor do I. But explaining what's actually taking place in detail is pretty
controversial (to say the least).

> > So what do we do about "tanning development"?

> If you meant where to place tanning development between bleach and
> tanning, it's tanning. Also, for photographic purposes, tanning =
> crosslinking = hardening. The word tanning is more commonly used when
> hardening is achieved as a result of development. This is probably
> because oxidized developing agents in the form that can crosslink
> gelatin can also polymerize and these make colored insoluble products.

Based on the litterature and patents I saw, I don't think I could agree with
that "classification".

Martin

>
> > Maybe, maybe not, that's why I suggested to give it a (practical)
> > try. As e.g. the highly disputed subject of chrome
> > hardening-crosslinking-tanning suggests, there seem to be areas
> > where theory may be way behind practical tests. Maybe oxidized
> > metol is different from what the theory about "tanning development"
> > predicts. Incidentally, I am aware of at least one case where a
> > metol/ascorbic acid developer was said to harden a silver halide
> > emulsion.
>
> I don't think crosslinking mechanism of chromium is disputed.
>
> Also, I am not doing photography for sentiments of amateur
> chemists. I'm merely using chemistry to achieve what I need to
> do.
>
> > So what do we do about "tanning development"?
>
> How can you argue tanning action of hydroquinone, metol, whatever,
> without knowing the current state of knowledge?
Received on Fri Jul 15 11:16:09 2005