Printing gum on hard surface

I am making sheet after sheet of clear hardened gum for chemical
analysis, and have a couple of observations to share:

James recommends exposing the heck out of gum when you're putting it on
a hard substrate. I don't understand this advice at all, since it's not
consistent with what I know about gum. It seems like the idea must be to
somehow "nail" or "glue" the gum to the substrate by more exposure, but
in my experience gum doesn't work that way. If the substrate is too
slick to hold the gum, I don't see how extra exposure is going to make
it stick any better.

But never mind that, I dutifully overexposed as instructed, but after a
while I got tired of clearing the resulting dichromate stain and went
back to exposing the way I normally expose, and I can now report that
in my experiments on glass and on mylar, overexposing made no
difference in how well the gum stuck to the substrate (would not stick
on glass no matter what; stuck well on scuffed mylar no matter what) or
on how much hardened gum was produced. It seems there is an optimum
exposure beyond which exposing more doesn't give you any more hardened
gum; all it gives you is dichromate stain without compensation. Working
with unpigmented gum on a non-absorbent surface, you can see that very
clearly.

I think I wrote on my gum printing website that people might be less apt
to get intimidated, confused, or hung up on irrelevancies if they would
keep in mind that the gum process is about hardening gum; that's all it
is when you come right down to it. This project has if anything made me
even more sure of this.

I know that many people recommend subbing for printing on glass; for my
purpose, subbing was not an option because there needs to be nothing on
the surface but pure insoluble gum. And scuffing didn't seem to help, or
I didn't scuff it enough. The chemist I'm working with thought it would
be a simple matter to coat glass with dichromated gum, expose, wash and
dry it and then peel off a sheet of nice hardened gum. Don't I wish! I
told him that if it were that easy there would be thousands of students
making tents and lampshades and patchwork quilts out of gum prints
lifted off their substrates and laced together. But I digress.

I know there are people here who have a lot more experience with
printing on hard surfaces than I do; I'm just sharing what I've
observed while working on this project, for whatever it's worth to
anyone.

Katharine Thayer
Received on Sun Sep 5 08:26:24 2004