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Re: platinum/palladium coating
"Christina Z. Anderson" wrote:
> What is the longest time anyone has gone successfully between coating
> the paper and exposing it?
> Am I correct in assuming that the longer time will affect contrast,
> making it lower, and after a certain too long length of time, fog the paper?
> Should one use silica gel to keep the paper dry during storage?
It is recommended that exposure commence immediately after finishing the
coating (including drying). The coating can be dried to anywhere from
5% to 70% relative humidity and produce consistent excellent results
(although different humidity can produce differences).
A time of more than one hour between coating and exposing might cause
some noticeable degradation. Four hours will definitely show
degradation.
Contrast may or may not be affected. Some observed degradation has been
a loss of quality and substance, lessening of maximum blacks, a
formation of graininess, fogging, and muddiness. Any combination of
these may occur to varying amounts.
I have tried hermetically sealing a coated paper and found it to still
degrade the next day (even if kept in the freezer). Simply keeping the
paper dry does not work as the coating seems to change over time alone.
Also, I have had exposure times of between three to four hours which
have worked OK, but I would not let the coating sit that long before
starting the exposure (it will show degradation).
Recommendation is to not store the coated paper. Plan on exposing
immediately after coating is dried to desired level. Somtimes it can
take 10 or even 15 minutes to dry the paper properly.
Another important consideration is to apply the coating mixture
immediatly after mixing. Do not mix a coating solution and let it sit
around before coating as several things could go wrong.
--
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/