Gum hardening: top down?

Okay, I've coated a very thick, very heavily-pigmented gum emulsion
on mylar and printed it from the front and from the back. A couple
of comments before I give you the URL:

(1) though the emulsion was very heavily pigmented, two things
resulted in not a very deep DMax: (a) the fact that I used ivory
black, a transparent pigment (if I were to do it again, I'd use lamp
black) and (b) the fact that it's printed on a transparent material
and was scanned as a transparency, with the light shining through it.
But the thing to note is, be that as it may, the DMax is about the
same in both prints.

(2) there's a light brown pigment stain (ivory black is a brownish
black) in both prints that is probably a function of the heavy
pigmentation. It hardly shows in the prints themselves, but for some
reason was accentuated in the scanning.

(3) I don't honestly know what to make of the results. If you look
just at the prints on mylar, you'd have to conclude that back-
printing is much superior to front-printing, at least for a thick
coat on mylar. But if you compare the back-printed print on mylar to
the regular front-printed gum print (using a less heavily-pigmented
emulsion) on paper (at the bottom of the page), it's hard to claim
that the back-printed print is superior. But since they are on
different materials, it's apples and oranges.

So I guess if I were forced to draw a conclusion from this rather
inconclusive test, I'd say that if you are going to print on mylar
using a very thick and heavily pigmented emulsion, then you'll
probably do better printing from the back. But if you're printing on
paper, you can get fine results printing from the front with a less
pigmented emulsion.

http://www.pacifier.com/~kthayer/html/topdown.html

Katharine
Received on Mon Apr 10 12:33:18 2006