Cor Breukel
http://ruly70.medfac.leidenuniv.nl/~cor/cor.html
"The Infrared Gallery"
http://ruly70.medfac.leidenuniv.nl/~cor/ir-gallery.html
---------- Forwarded message ----------
Date: Tue, 13 Jan 1998 03:37:03 -0500
From: Harald Leban <HLEBANPHOT@compuserve.com>
To: Alt-Photo-Process-List <alt-photo-process-l@skyway.usask.ca>,
Harald Leban <hlebanphot@compuserve.com>
Subject: PMK-Modification against uneven(Oxygen) staining
Hello alt´s
When I look for the latest correspondences about the pyro-developing it
seems to me if most of you have equal problems with PMK like myself.
The uneven staining and high base-fog problems in tray and also in
rotation-developing let me think about the reason-why.
I think the main problem is the air-oxydation combined with the relatively
long developing time. To eliminate these facts should clean my problems and
negatives.
I made two modifikations on Hutching´s PMK:
The first, to slow down the air-oxidation of the working solution, I added
ascorbic acid as antioxidant to solution A.
The second, to cut the developing times, I concentrated the working
solution (added more pyro and metol but also a small amount Potassiumbromid
against fogging to Part A).
Since I used this modifications I never had problems with the results on
HP5+, FP4+, T-Max 100.
For mid- and large-format this corrections have no bad effects on negatives
(grain, sharpness etc..)
So try it - and you have some problems less.
When you work with ready to use packs from photographers formulary or
others you should use only 75% quantity water to make Part A and add the
ascorbic acid and Potassiumbromid.
If you make it yourself try his:
Rezepture PMK mofdified by H.Leban
PartA
800 ml aqua dist.
20g Sodiumbisulfit, Sodiumhydrogensulfit
20g Metol
150g Pyrogallic acid
10g Ascorbic acid(Vit-C)
1,5g Potassiumbromid
2-5g EDTA-Na4
Part B
300g Kodalk, Sodiummetaborat
5g EDTA-Na4
in 1l aqua dist.
For normal and N+/N++/N+++ developing use: 1PartA + 2Parts B + 50 Parts
water
Times for HP5+(at 400 ISO) 22°C(72°F) Rotation-Jobo
N/6,5min
N+/8min
N++/9,5min
For normal and N-/N- -/N- - -/N-3 developing use: 1Part A+2PartsB+ 100Parts
water
Times for HP5+ (at 400 ISO) 22°C (72°F) Rotation-Jobo:
N/8min
N-/6,5min
N-2/5,5min
These are my processing dates to get 8x10" negatives for platinum/palladium
- maybe you have correct it for your work.
I also process FP4+, T-Max100, Lotus View Classic100 and T-Max400 with best
results.
If you need a detailed Rezepture sheet and times for other films please
contact me directly.
Greetings from Austria
Harald Leban
chemist and alt-photographer
hlebanphot@compuserve.com
Platinum prints at: http:\\www.aperture-photo.com (the platinum room)