Liam Lawless (lawless@vignette.freeserve.co.uk)
Wed, 03 Feb 1999 01:05:11 +0000
Hi Gary,
I'm sure you'll shortly be inundated wth messages, none of them brief, but
I'd like to mention what I consider to be one huge benefit of PMK, but which
no-one else seems to have picked up on.
As well as being clumsy (see my glyoxal message), I'm absolutely hopeless
with a paintbrush and therefore do not bother to spot silver prints - if it
don't come out right, it goes straight in the bin. I always had terrible
trouble with spots on prints despite taking every reasonable precaution; not
polka dots exactly, just tiny little specks, but if there's a speck in the
sky I'll find it, and having found it the print is ruined for me. (Funny
thing, though, I'm not nearly as critical when looking at other people's
work.) Anyway, I finally concluded that it was something to do with the
water (very hard round here).
This might be right or wrong, but pyro, being a tanning developer, hardens
film as it develops, and in fact hardens in proportion to the developed
silver densities. Now the trouble I had with spots on prints was due to
dirt, dust or other crud - whatever the source might have been - getting
onto my wet films. (Since I used filtered water and a filtered drying
cabinet, I believe it must have been the water; in certain circumstances I
think the calcium in hard water can agglomerate to form particles big enough
to cause problems.) Now in normal developers the gelatin of the emulsion
layer swells considerably during development, and contracts again as it
dries after the final wash, and any foreign bodies that find their way onto
a swollen wet emulsion tend to become trapped as the gelatin contracts,
whereafter they are all but impossible to remove.
Since a tanning developer hardens the film as it develops, the emulsion
layer does not swell during processing and all the rubbish that used to get
stuck to my films now flies away with a couple of puffs of the blower brush.
A spot on one of my prints is now the exception rather than the rule, and
I'm eternally grateful to Monsieur Hutchings for bringing pyro to my notice.
As a matter of interest, someone mentioned pyrocatechin (a.k.a.
pyrocatechol, or just catechol) the other day. I tried this probably 8-10
years before I'd even heard of PMK: it produces a weaker stain than pyro,
but also tans and gives the same sharpness, but the fog level of the first
film I developed seemed so high (which I now know to be due to staining)
that I thought something had gone wrong and didn't even bother to print the
film, or try it again. Wasn't that silly?
Liam
-----Original Message-----
From: Gary Miller <gmphotos@earthlink.net>
To: Alternative Photo Group <alt-photo-process-l@usask.ca>
Date: 02 February 1999 20:03
Subject: Pyro & Ag negs
>Could someone from the 'pyro group' please tell me briefly the advantages
of
>using Pyro to develop negatives that will be used for making silver prints
>and also enlarged to 8x10 for alternative printing.
>Thanks.
>
>Gary Miller
>
>
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