>Also a chemist at Engelhard Corporation, Specialty Chemicals Division
>(where I purchase my metal salts) told me that K2PtCl4 could convert
>into K2PtCl6 at temperatures as low as 140F. It seems that K2PtCl6 is a
>more stable salt. And, that this conversion is definatly aided by the
>presence of sodium.
This is true, but you are going to have to come up with some Cl2 for this to
occur. I appreciate you spending the time to put forth your observations in
this matter. One of the benefits of the List however, is to go beyond the
formulaic. Rather than just describing what happens when certain conditions
are set up, to get to the "why", the science of it all.
It is not always possible to get to the science. If I could get Los Alamos
up the hill from here to devote a year to studying platinum printing, I bet
we'd learn something. Fat chance. Next best thing is the group mind here on
the List. There are some real chemists here, (not the garage trained variety
like me), who may be able to shed some light on issues like the one you raised.
In over 15 years of providing a help line for platinum printers we have
heard so many conflicting theories about platinum printing. Often told in
absolutes. "You can print on that paper", "You can't clear with that", "You
have to humidify the paper", "You have to dry the paper". I am sorry if I
may have become jaded when people make such proclamations. My ears perk up a
little more when the science comes along with it.
I have made a ton of platinum and palladium salts in the last 15 years --
well literally at least. I have done some testing along the way. I still say
that K2PtCl6 will not produce black specks in a print. Something else may be
going on. In every case we've been able to nail down, black specks have been
caused by two things. Either ferrous metal contamination or on rare
occassions the K2PtCl4 kicking out Pt metal. Making the K2PtCl4 is a tricky
process. By its nature it is an unstable chemical, that's the plague all
photographers have to live with, to be sensitive to light or work in light
sensitive systems, they must be unstable. nop51076@mail.telepac.pt (The chemicals not the
photographers.) I've seen batches from big name chemical companies that were
embarassingly bad.
I am interested in any other opinions in this issue.
Dick Sullivan
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