Re: Reversal processing for enlarged negatives

From: Richard Knoppow <dickburk@ix.netcom.com>
Subject: Re: Reversal processing for enlarged negatives
Date: Wed, 24 Mar 2004 20:40:43 -0800

> Is KRST better than KBT or a solution of Sodium Sulfide?

Well, in my early posting I made a range of suggestions to try and
find the best one for each application. There, I listed sulfide,
polysulfide, alkaline thiourea, and KRST. Sulfide and polysulfide have
definite disadvantage of hydrogen sulfide gas, which is a potent
fogging agent for the exposed material, at any point before the
completion of the first bath. Liam Lawless said his experience was
that sulfide redevelopment resulted in very high UV density. I don't
have any definite explanation for that. So far, KRST is free from a
reported case of undesirable effects. I wouldn't say it's better.
Also, I'm more curious about what is causing high UV density in the
case Liam mentioned.

> Sulfide has been used as a reversal "redeveloper" in the
> past but results in a sepia image. I am wondering about the
> ammonium thiosulfate in KRST or is it not there in
> sufficient quantity to fix out enough halide to matter?

Ammonium thiosulfate in KRST is there to make selenium toning reaction
rapid. As you say, the concentration is too small to compete with the
rate of toning reaction.

> Will KRST result in a more neutral image?

That'll depend on the size and morphology of the grains that
result... you know all that stuff.

> I have never
> tried KRST as an indirect toner but understand that it can
> be used that way, which would be similar to its use for
> reversal.

I sometimes do, but the way I do involves selective bleaching, partial
fixing and full toning. Depending on the paper, developer and bleach,
I get different hue but it tends to be on blue or greenish
side. Nothing like the ugly green of partially exhausted MQ developer
with modern enlarging papers, particularly because I make the rest of
the print jet black or purplish...

--
Ryuji Suzuki
"All the truth in the world adds up to one big lie." (Bob Dylan 2000)