Cor Breukel (cor@ruly46.medfac.leidenuniv.nl)
Thu, 18 Mar 1999 09:07:07 +0100 (MET)
Zia and Gold: Some observations
In the past I had considerable problems with graininess when using
goldchloride in the Ziatype system. Thanks to Carl, Dick and the nice
website of Nze Christian (next to the nice images he has put up recently
he added a few pages on the technical details of Ziatypes, amongst others
a set of sample images demonstrating the different colour possibilities.
Worth checking out at: http://ourworld.compuserve.com/homepages/nzec). I
did not solve the graininess but reduced it considerable.
"Testing system"
-Ziatype kit (as sold by B&S about 2 years ago)
-Paper: Simili Japon
-Rod coating
-Humidity: around 65%
-Temperature: 20-22 oC
-Negative: 4*5 inch redeveloped in Pyro
-Wash for 2 minutes in running water (face down), clear in citric acid (30
gr to a litre, twice the normal strength, raised it because I had troubles
clearing )(face down) for 5 minutes. Changing the solution for a fresh one
for every new print!.
( a ps: when I put the print face down in the clearing bath, small
airbubbles start to form quickly on the back of the paper, and leave
rapidly, could not detect them when turning the print around, probably
they got released by the turning. Any idea why this is happening?)
Wash for 10 minutes (face down).
First I tested the influence of drying time by mixing 50% gold and LiPd
(replacing half of the volume LiPd with the goldchloride, so the actual
end percentage would be 25% since one adds an equal amount of ammonium
ferric oxalate) by printing Stouffer step wedges after 3 minutes of drying
(by air; my shortest time) upto 20 min. No significant difference observed
(maybe not so surprising seeing my humidity at 65%). The higher steps
showed the lavender colour, with a little bit of grain. The lowest steps
turned brown with some bronzing, not a very nice colour; weak Dmax.
Next I tested the addition of Tween20 (25ul Gold + 25ul LiPd + 1ul 10%
Tween + 50ul Amm. Ferric oxal. Note: ul stands for microliter; 1/1000 of a
millilitre). The coating of this emulsion was much less smooth then
without the Tween, but it give a slight but clear better/darker Dmax but
only on the shortest dried test strip.
Next the real thing: I printed the 4*5 inch (a nice old tree without
leaves against a clear sky) negative for 12 minutes with different
percentages gold and 2ul of Ammonium Dichromate (in a total volume of 300
ul). Colours compaired to a 50/50 LiPd/CsPd print
% Gold
25% : A nice tinge of lavender in the sky, the tree slightly more brown
than the reference print
30% : More prominent lavender in the sky; tree brown with a hinge of
blue/grey
37.5% : Pink sky, brown/lavender tree trunk
50% : White sky (Increasing gold means increasing contrast, should have
left the dichromate out, or reduced it). Lavender/purple/blue tree shadow
parts a rusty brown, a bit too off to my taste.
The possibilities are quite big; from an almost undetectable tinge to
surreal colours. The grain only appeared in some parts of the sky, hardly
noticeable and not at all distracting.
Worth pursuing further!
Cor Breukel
http://ruly70.medfac.leidenuniv.nl/~cor/cor.html
"The Infrared Gallery"
http://ruly70.medfac.leidenuniv.nl/~cor/ir-gallery.html
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