Re: glyoxal yellowing now: How do you know it's hard?

Another approach consists of using silane for the subbing: rub the
(clean/degreased!) glass plate with a 1% freshly prepared acetone solution
of 3-aminopropyltriethoxysilane over one or both sides with a tissue for
about 1 min until the solvent has evaporated. Allow the glass plate to stand
for several hours to ensure reaction of the silane. On that layer your gum
solution will firmly adhere.

Some time ago (maybe in 2002 or 2003 - take a look at the archives) Philippe
Monnoyer recommended incorporating silane into a gelatin solution. It may be
a good idea to add a small amount of that above mentioned silane mixture to
your gum solution.

Martin

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, February 04, 2005 3:35 PM
Subject: Re: glyoxal yellowing now: How do you know it's hard?

> Okay, so I've been thinking about doing some printing on glass, and it
> occurred to me that as part of that experiment I might as well test my
> speculation of the other day about whether perhaps hyper-crosslinked
> gelatin might provide tooth for printing gum on glass. This speculation
> rests in part on Chris's observation that glyoxal hardened gelatin is
> gritty, and in part on my own observations (in gum, not gelatin) that
> (1) more crosslinking beyond insolubility results in a gritty surface,
> and (2) that gum needs tooth of one sort or another to hang onto, so
> perhaps this crystalline structure, this grittiness, might provide that
> tooth.
>
> So this morning I mixed up some 1% glyoxal in gelatin (the equivalent of
> 25 ml 40% glyoxal per liter) and spread it on glass. It coated nicely on
> warm glass but there's a problem with using this to test my hypothesis:
> there's no grit. It's smooth to the touch and also looks smooth in
> angled light. So then I put the same stuff on Artistico Extra White, and
> that didn't feel gritty either. So I wonder if perhaps we have different
> definitions of gritty. I was expecting it to be gritty in the same way
> my glyoxal-hardened gum was gritty when I used too concentrated a
> solution of glyoxal. That was so gritty you could have taken paint off
> with it if you'd used it for sandpaper, and it snagged my skin when I
> ran my fingertips across it. But this is smooth on glass, as I said, and
> on the Artistico Extra-White it is slightly rougher than the fresh paper
> out of the box, but so is the same paper after it's been soaked without
> sizing; I can't tell the difference between the two.
>
> I have yet to try printing gum on this, but first I have a question.
> After the gelatin dried, I thought oh, I should rinse it before printing
> on it so it won't turn yellow. But then it occurred to me that it's
> going to get rinsed anyway when I try printing gum on it in the next day
> or two. So here's my question: does anyone have any knowledge of
> gum-printed glyoxal-hardened gelatin turning yellow later, or is this
> purely a phenomenon that occurs when people size paper and then leave
> it for a period of time before printing it? Sorry about not being
> entirely clear on that; I have watched the glyoxal threads with only
> half an eye or not read them at all, since it's never been something
> that related to my own practice.
> Katharine Thayer
Received on Fri Feb 4 22:28:01 2005