Ziatype: the result of my second test.

Hi all,

I have made a second test today:

I printed a 101 step and 21 step tablets (both digital - will print a real
21 step tablet tomorrow) applying a curve based on the uncurved first test.

My first test showed brownish/yellowish stain:
* It was developed in plain tap water
* I noticed that there were rust marks in my brush!!!

So, in todays test I used citric acid as developer and changed my brush (an
awful Pebeo brush - I have 3 sizes of Magic Brush but couldn't find them!!!
will switch to Magic Brush as soon as I find them)

The citric acid was around 2%-4%: four plastic spoons - smaller than table
spoons, bigger than teaspoons - in 2lt tap water.

These two precautions totally cured the stain problem! The print was cleared
in 1 minute! But I continued to develop the print in citric acid for 5
minutes (changing it two times) anyway.

See the result here (I tried to adjust the scans to reflect what I see as
much as possible but you know, web reproductions are not perfect!):
http://www.loris.medici.name/images/ziatype-test.jpg

What a lovely progression of tones (now I start to get what platinum
printing as all about!!!). There's some problem in 25%-20% (not enough tone
change) and 10%-5% (too wild tone change) - will fix it by playing with the
curve.

As you can clearly see, the density of the digital negative is not enough to
print paper white. I will have to use some kind of contrast agent - probably
ammonium dichromate. What is your suggestions about AD? I plan to start by
adding 1 drop of 25% AD to 25 drops of coating solution - is that too much
to start, should I start with a milder addition?

Another point: After the second test (which was exposed 2:30 - the first one
was exposed 1:30) I still think dmax is a little bit on the low side.

See a dmax comparison of my ziatype test with a double coated classic
cyanotype print:
http://www.loris.medici.name/images/zia-cyano-comparison.jpg

The cyanotype is marginally better in dmax (please note that my cyanotype II
prints are darker than my classic cyanotypes!). What can I do to increase
dmax? (I want it to be as much as or better than cyanotype 2 - the current
situtation may be considered as OK but I think it may be limiting for some
subjects)

Regards,
Loris.
Received on Tue Oct 12 16:00:13 2004