Re: Printing gum on hard surface

Coating a colloid on a glass substrate typically involves (prior to coating)
extensive washing (sodium/potassium hydroxide, nitric acid, chromic acid and
the like). Silane (e.g. 3-aminopropyltriethoxysilane) may be another step...

Martin

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, September 03, 2004 12:30 PM
Subject: 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 08:36:06 2004