Rotary Pyro Hints

KOUKLIS, KERIK T (Kerik.Kouklis@Aerojet.com)
Tue, 27 Jan 1998 14:54:44 -0800

Dick et al,

> Do they work with pyro? The Jobo is miserable with pyro do to the
> "slosh
> factor" causing oxidation....
>
> In the Jobo the stuff exhausts itself...
>
This effect is easily overcome. Simply mix twice the normal quantity of
Pyro, place 1/2 of the total volume in the drum or tube, rotate
(agitate) for 1/2 the developing time, dump out the now oxidized Pyro
and replace with the balance of the fresh developer and continue
rotating for remaining development time. Viola!!! Cello!! Violin!
works like a charm... In MY experience, nothing gives ME the delicate
highlight separation in MY platinum prints like FP4+ in PMK Pyro.

One caveat on the method listed above: Since the developer is highly
oxidized by the time you are done, you should not use the developer in
the pyro after-fixing-bath step. Rather, use a solution of sodium
metaborate at 1/2 teaspoon per liter of water. You should also avoid
acid stop baths (I use plain water), hardening fixer, and hypo clearing
agent(s). They all have adverse effects on the pyro stain.

By the way, I was told recently that
_at_the_relative_concentrations_in_the_PMK_formula_, the metol is
actually more hazardous than the pyrogallic acid. Either way, I make
every effort to avoid skin contact, and more importantly to NEVER breath
the dusts when mixing the stock solutions.

Kerik.

http://www.jps.net/kerik/