Eric Neilsen (e.neilsen@worldnet.att.net)
Fri, 21 May 1999 22:32:44 -0500
Here is a thought on the ZIA system (and other systems, traditional included
to some extent) at high humidity levels.
It may just well be that it is a case of too much water. What after all is
making the POP method work? Is it the ammonium in the system? I think not,
for if this were true adding ammonium to both the platinum salt and the
palladium salt would give a POP, and it doesn't. Ware cautions in his
Investigation of Platinum printing, against printing at excessive high humidity
levels. Perhaps what you are seeing is a solarized palladium. All that water
and the reaction just keeps taking place, nothing to slow it down or exhaust
it. Between the coating solution absorbing too deeply into the paper, and
excessive water,. which with POP is a reactant, you have a reaction that just
goes like a little pink bunny, but in this case, deep into the paper fiber and
faster than expected. As Carl has noted, too much solution seems to be more a
problem at high humidity, and indeed Jeffrey has show that with his over coated
results, too much water will not over come "extra" palladium. What after all
makes this a self masking process? Palladium? Ammonium? or Water? no more
water, no more reaction.
It does seem clear that more palladium can safely be added to the common Zia
formula. What can not be safely added in solution should easily be added by
changing the ratio of ferric to metal salt.
As Nze, Carl and other agrees on, it looks like an RH of between 55% to 65% +/-
5 seems to produce the best, most predictable results; with special
considerations aside.
What I have yet to see in Jeffrey's results is how much time is allowed for the
paper to "stabilize" to an RH. Just because a paper is in an environment of a
specific RH does not mean that that paper is at that RH unless appropriate time
is give to allow the paper the climatize.
-- Eric J. Neilsen 4101 Commerce Street, Suite #9 Dallas, TX 75226 214-827-8301 http://home.att.net/~e.neilsen
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