Richard Sullivan (richsul@earthlink.net)
Fri, 21 May 1999 08:46:37 -0600
>Next I tried a coating of:
>Sensitizer at 24 drops of 40%
>Contrast agent of one drop 0.75% Potassium Chlorate
>24 drops Li2PdCl4 at a concentration of 24.49 %
>
>This resulted in the most neutral color AND no warm color blotches.
>WOW! It seems that the Ammonium Dichromate may be an undesirable
>ingredient of the coating. Past experience has shown me that more
>Potassium Chlorate is needed to produce the same contrast as Potassium
>Dichromate so I assumed it might be the same for Ammonium Dichromate.
>The 1.5 times seemed close, but a more accurate comparison should be
>done.
>
>I plan to check on the optimization without using Ammonium Dichromate.
Jeff,
Interesting results on the ammonium dichromate but it doesn't jibe with my
experience or that of most of the callers I talk to on the help line. First
off I would expect unevenness of blotchiness to be of mechanical origin and
not chemical. In other words, the print is not evenly humidified. I have
made thousands of Ziatypes with ammonium dichromate and have not observed
this in any case other than with uneven drying.
When a print is too wet all kinds of strange things happen. When too dry it
tends towards brown and with pure LiPd it tends to grain up real bad.
It is great that you have taken up the cudgel and are doing some serious
exploration of the Ziatype parameters. As you can see, the Ziatype process
has a great many of what I call personal variables. Since each person will
introduce a slew of little changes in the way the paper is coated, dried,
and printed, it is very difficult to validate the results in an objective
manner. You become acutely aware of this when trying to help a printer
solve problems over the phone. I often hear, "I am doing it exactly as it
says to do it in your book." The other chorus is "It worked before and I
haven't changed a thing."
Cheers.
--Dick Sullivan
--Dick Sullivan
505-474-0890 FAX 505-474-2857
<http://www.bostick-sullivan.com>http://www.bostick-sullivan.com
http://www.workingpictures.com
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