From: Christina Z. Anderson (zphoto@montana.net)
Date: 03/10/03-09:10:28 AM Z
"The problem I seem to be having is that the shadow areas of the prints show
splotchy areas of solarization/bronzing with an exposure of 2-3 minutes. The
more exposure I give, the worse the problem gets and the lighter the shadow
areas become. A curious aspect of the problem is that it only occurs where
the negative is - the borders of the print (not covered by the negative)
just get darker with more exposure. The less exposure I give, the darker the
shadows get and the less highlight detail I have." (Scott)
Scott,
I may be sticking my neck out here--no, not *may*, but *am*--but I'll
offer my research for whatever it is worth on solarizing/bronzing. The
research is from as far back as late 1800's to now on the alt list. It
seems no one has the definitive answer for the issue, probably because
there are a number of variables.
Mind you, I have never done kallitypes, only pt/pd, and I did get
bronzing.
First of all, is it possible that the added gum is keeping more
moisture into the solution than you think? I mean, gum can be dry to the
touch but still have some moisture? A chemist might be able to answer
whether little bits of moisture are left in suspension in the stuff.
Anyway, my solarizing bronzing notes, below--feel free to refute or
accept any as truth :)
Chris
1. Under Kallitype:
Dampness exacerbates solarizing, so dry paper thoroughly.
Too long an exposure also leads to solarizing. Toning will correct
some of it. So will adding additional silver nitrate, so says Farber.
Excess humidity will lead to speckles and streaking.
Mottling or a decrease in density: use more dilute toner or different
paper and sizing.
2. Under Pt/pd:
Bronzing: Not enough ferric oxalate in the mix, negative is too dense and
therefore print times are too long, paper is not dry before printing or
becomes moist while printing due to heat and humidity.
Abney back in 1898 seemed to think it only happened with sun exposure.
He described it as an orangey granular look that darkened in cold water
development to blocked up black. He suggested it was iron reduced
completely at those spots, or iron converted back to ferric, due to one or
two contributing factors: too much exposure with a thin negative, for
instance, or dampness in the paper while exposing. The remedy of course
would be no sun exposure, don't use thin negatives, don't overexpose, and
use a weaker, cold developer to at least resurrect a damaged print.
Here are some other suggestions: one author says to coat palladium
heavily, put sizing in the sensitizer, and increase the metal in proportion
to the sensitizer (seems to contradict the 'not enough ferric oxalate,
above). Apparently palladium is more prone to this problem, by the way.
Alt list says this: "This can be attributed to improper coating. When
too much of the coating mixture puddles or dries too quickly leaving a thick
layer on the surface rather than in the upper surface of the paper, this can
occur. The "bronzing" may also occur more easily when certain materials are
used. I have made many Pd prints without Pt without any problems, and have
noted "bronzing" when Pt was also present. In some instances "bronzing" may
be thought to be solarization, but is likely caused with high humidity, high
temperature exposures. This type of "bronzing" can occur no matter how good
the coating is. The tendency to bronze can be from a thin coating, which is
faster than thicker coatings, and therefore will be reacted on more quickly.
It will not be able to give a good black.
A thin coat of sensitizer with or without pt will look weak, and may be
called "bronzing". With the price of palladium these days, I would
certainly think that a pinch of pt may help. I rarely use less than 25% pt.
The high temperature/ high humidity are both friends to palladium's speed.
It would be nice if someone could quantify this bronzing effect. It
must depend on more than just over exposure. I have a particular negative
that requires almost a three hour exposure and the uncovered edge coating
does not display any signs of bronzing nor solarization.. Typical exposures
are 6.5 minutes with this light source. At higher than 80F temperatures and
higher than 70% RH, I have noticed some random bronzing and solarization
effects. However, I do not know of any conditions that can consistently
produce the bronzing effect.
My students consistently get the bronzing effect in the edge coating
and sometimes in the most open parts of the negative when they overexpose
palladium prints. Ernestine Ruben said that one or two drops of platinum
mixed with the palladium could prevent this from happening but we have not
tried that solution.
I've seen the same kind of solarization - though I hesitate to call it
solarization because the areas where it happens go to that bronze color
rather than just losing density. And I can attest that a little bit of
platinum added to the palladium prevents it. Whether it happens also seems
to be related to the quantity of contrast agent."
This archive was generated by hypermail 2.1.5 : 04/22/03-02:37:25 PM Z CST