[pure-silver] Re: Chemical Fogging in Reversal Processing

> Thiourea is probably being used as a redeveloper in place of sulfide. The
> result is a sepia image of sulfide. Because either Thiourea or Sulfide works
> directly on the halide it does not need a fogging exposure or chemical fogging.
> It also eliminates the need for a final fixing step because all of the halide
> is converted to sulfide whereas there is always a small residual of halide
> which is not made developable by flashing. I am uncertain about the effect of a
> chemical fogging agent but would guess its the same as the use of Sulfide, that
> is, no final fixing step is necessary.
>
> --
> Richard Knoppow
> dickburk@xxxxxxxxxxxxx
> Los Angeles, CA, USA

Is this situation with Thiourea/Sulfide unique, or do you think it's more
generally true that if a toned result is desired from a B&W reversal image that
the fogging - second development steps can be bypassed or would likely be
easy to incorporate in the toning process? 

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