From: Gregory Parkinson (glp@panix.com)
Date: 06/21/00-05:15:14 AM Z
I've now had three sessions of my etching class - the first two sessions
were just etching basics, and then monoprints to loosen up those overwhelmed
by the positive/negative & chemical processes. The third session was
this last Monday and I got to try their photoetching process. The plates they
use are "water soluble" (dunno the manufacturer) and the photosensitized
resist that has been exposed to light develops off, allowing the those parts
of the underlying plate to be exposed to acid and etched in the acid bath.
Using a plate, there are two ways of getting ink onto paper -
using a hard roller you lay a coat of ink onto the high (un-etched)
parts of the plate, or you smoosh ink down into the etched parts
and rub it off of the high parts (and you can combine them, something
I was shown and am still getting my arms around.) Using their
photo plates, exposing with a positive transparency gives you
a plate with the black unetched - so you roll the ink onto those
parts and print. Exposing with a negative gives you an intaglio
plate where the black is expressed as etched pits on the plate that
you rub ink into to make a print.
We made the negs from Photoshop on a <???> printer (I was late
for class and had to rush through the printing) onto Vellum. This
worked well with a halftone screened negative but not so well for the
unscreened negative, because I knew I needed to move the
blackest areas to less than 100% black in order to get dots in
the plate in those areas but took a radical guess of 50%, which
caused the plate to be way overexposed (but I fear that if I reduce
the exposure I will lose the contrast range - time will tell).
I'm working on a set of test images that include step tablets, and
am wondering if anyone on this list has ventured into this area of
making digital negatives for photoetching.
Greg
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