Thanks for the R&D Chris. I'm interested in the idea that longer
exposure times equates to better plate durability.
I'm actually in the process of testing the KM83 plate, which has a
slightly thicker polymer layer than the KM73. I've found increasing
both exposure times by 25% (a tip from Harold Kyle) gives it a look very
close to what I've been getting with the KM73s. Having tried this I
infer the idea of ratios is such that I couldn't simply increase both
exposures by 25% and get the same result. I assume if I increased
exposure times by 25% with the KM73 I'd have blown out highlights.
Based on your notes, I'm assuming here that the ratio shifts by some
factor as the exposure times increase or decrease. I'm wondering if you
have some data on what that factor might be (yes, I'm being lazy). Of
course I could always try this in conjunction with getting on board with
PDN later this summer...
Also, how do Elizabeth Dove's screens differ from Dan Welden's? Do they
use a different pattern? More or less coarse? Thicker plastic?
I'm glad you came to the same conclusion about point source. It's been
cited several places as you know, but it's good to have data as to why
UV tubes are more prone to problems in any case.
Christina Z. Anderson wrote:
I've proven successfully (to myself) with outside exposures why there
is such discrepancy between exposure times between different
practitioners. Eli Ponsaing set me up to this--I blame him--with his
30 minute combined exposure time (computing to a ratio of 1:4 aquatint
to positive with inverse square law of light). It makes perfect
logical sense because of the following experience: when exposing any
plate and then putting it in the water, the parts of the plate that
should be hardened to paper white, even with gross overexposure, still
give off some gunk in development if you wipe it with a finger. In
other words, there is thickness to spare.
I've exposed plates at all kinds of different combinations of times
and they've all produced good images (alas, step wedges only...with a
few parts of images cut and pasted on the side). This parameter of
exposure time is much less for KM73s, because they in general are a
thinner coating on the plate (or perhaps the different
ingredient--nylon?--responds differently) but both solarplate and
KM73s respond to exposure by hardening a thickness (vertical) of a
layer and hence, the ratio of time of aquatint to positive is really
the critical one that has to be found out based on exposure time
choice, light unit, etc.
To give an example, I exposed a solarplate for 1 hr each exposure (2
hr total) and still got blacks and whites in the image, and had gunk
to spare that developed off the plate.
So the real issue is to settle on an aquatint time that gives a nice
rich black and then choose the positive to run the tones up and down
the step wedge scale accordingly.
Jon, comparing sun (point source) to UVBL, I am having much less
problem getting a deep velvety black and have finally confirmed that
the mottled areas of pale in the blacks is diffused light leaking
under the substrate where incomplete contact occurs which is different
than the black dots that are newton rings--one is incomplete contact,
the other too complet contact, almost! BUT, I have not been getting
either in the sun the last 10 plates with my quite lengthy exposures
and am wondering if not enough exposure can contribute to either
issue--just an hypothesis at this point (no pun intended). I
definitely uphold your philosophy to stick with point source
light--much less problematic. Ha ha, I've gotten such a velvety black
outside that the entire image of a nude on a rock was so low key the
highest highlight was about a Zone 4--and THAT with a combined 30 min
I also have found that a MUCH sturdier plate can be had with
I also now understand why Dan Welden can be so loosey goosey with
solarplate, doing workshops and exposing in the sun like he does. It
actually works really well outside, so those without lightboxes, go
try it. But buy an etching press first...
Elibeth Dove's screens are wonderful. Unfortunately (why do I NEVER
learn????) I was doing some salt printing in my darkroom and
splattered silver nitrate on my aquatint screen unbeknownst to me. I
don't remember doing it at all. BUT I kept getting these white spots
on my plates (a new phenomenon--white spots the size of a small drip)
and finally checked my screen and saw these splatters. $30 down the
drain. It is amazing where silver nitrate appears when you least
One and a half weeks left of school and counting!
PS Susan, I tried to check out that chine colle thing on Graphic
Chemicals and couldn't seem to access it, if you remember posting this
maybe a month ago...thanks for the URL...
- From: "Christina Z. Anderson" <firstname.lastname@example.org>