[rollei_list] Re: OT Pyro & other developers WAS:Rollei Retro Film
- From: "Jeff Kelley" <jlkphoto@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Tue, 26 Feb 2008 09:37:39 -0800
Richard, thanks for the detailed info. You wrote "All ancient history" in
your reply but there has been somewhat of a revival of interest in B&W and
various newer formulae, especially Pyro variations.
For example, 510-Pyro from Jay DeFehr gets rave reviews from most users:
ascorbic acid 5g
pyrogallol 10g
phenidone .25g
Triethanolamine 100ml
The concentrate apparently has near infinite shelf life vs. other Pyro
developers. The above concentrate is mixed 1:100 with water for a one-shot
staining developer.
I've mixed up a batch but have not had a chance to try it yet.
Jeff
On Mon, Feb 25, 2008 at 11:22 PM, Richard Knoppow <dickburk@xxxxxxxxxxxxx>
wrote:
>
> ----- Original Message -----
> From: "Jeff Kelley" <jeff@xxxxxxxxxxxxxxxxxxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Monday, February 25, 2008 10:17 PM
> Subject: [rollei_list] Re: Rollei Retro Film
>
>
> > Richard Knoppow wrote:
> > Even though some modern B&W films have very hard
> > emulsions not all do and there is still some advantage to
> > the hardener in preventing damage to the film when its wet
> > (the hardener has little or no effect on dry film).
> >
> >
> > Richard, is it true that staining developers like Pyro
> > harden the emulsion &
> > therefore eliminate the need for adding a hardener to the
> > fix or stop bath?
> >
> > Jeff
> >
> Pyro and some other developers, hydroquionone under some
> conditions for instance, cause differential hardening of the
> emulsion. While the same reaction products that cause
> tanning are not the ones that cause the stain image they are
> similar in that the effects are proportional to the image
> density. Pyro developers leave a sort of relief image which
> can be seen when the negatives are viewed by reflected
> light. When used on unhardened gelatin Pyro developer can be
> used to form a matrix image of the sort used for dye
> transfer work although I think the developer supplied by
> Kodak for dye transfer used a different developer.
> Because Pyro has relatively little effect on those parts
> of the emulsion bearing a low density image it probably does
> not protect them from wet abrasion.
> BTW, a side effect of the differential hardening is a
> small change of the index of refraction of the gelatin. This
> can produce a small acutance effect at the borders of high
> and low density areas. There is also a variation in the
> swelling of the emulsion which can cause a further acutance
> effect due to a variation in developer penetration, plus
> there can be some slight geometrical distortion of the image
> due to the variation in shrinkage. For the last reason Pyro
> developers designed for aerial photography are usually of
> the non-staining type. Note that Pyro in the presense of
> enough sulfite will not generate enough of the reaction
> products of development to cause either staining or tanning.
> While both effects are considered desirable now they were
> not at one time and a considerable amount of work was done
> in devising non-staining Pyro formulas especially for motion
> picture use where the stain could be misleading in judging
> the contrast of negatives (development by inspection was the
> rule in the silent period) plus the exagerated edge effects
> caused by the tanning could result in quite noticable "edge
> crawl" on prints especially if a duplicate negative was
> used. All ancient history.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
> ---
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