Sizing with hardened gum

People have asked off and on about sizing with gum. Of course sizing
with unhardened gum doesn't work, because unhardened gum is highly
soluble even in cold water, and mixing the gum with dichromate and
exposing it has always seemed like too much trouble to me.

This morning for the first time I thought about the time I hardened
gum-pigment with glyoxal to paint with, thought of that in terms of gum
printing rather than painting, and it occurred to me to wonder why I
haven't ever thought of using glyoxal to harden gum to use for a size
for gum printing.

So I did some experiments this morning. I didn't get the mix exactly
right; it was thick enough to streak a bit, and the streaks showed
through (hardly, but I knew they were there) in the gum print. So if
you're going to try this I would use a little more water than I used.
What I used was 10 ml gum, 10 drops glyoxal (which measured out to about
.4 ml) and maybe 5 ml water (some of the water was in the brush, as I
used a wet brush, so it's hard to give a precise measurement of the
water.)

First I put some pigment in the gum-glyoxal mix and brushed it on the
paper and dried it, and then put it in water to make sure that it was
actually hardened. The gum didn't dissolve or loosen from either paper.
The most dramatic demonstration of the hardening of the gum was on
yupo, the gum lifted off in a beautiful pleated veil of insoluble gum,
just like it looks when you lose a layer of crosslinked gum off glass or
any slick surface.

The size worked differently on the two papers I tried it on. It worked
beautifully on Fabriano Artistico Extra-White, making a very crisp,
nicely detailed gum print. On Arches Bright White, it didn't work so
well; the details softened noticeably, although as a rule this paper
prints the sharpest details of any paper I've ever used. But since I
only did two little prints, this shouldn't be taken as a definite
conclusion; it could simply be sampling error or that they weren't
equally dry (I sort of rushed the sized paper through the drying
process.) But with both papers the whites were pristine white and there
was no speckling or graining of the print.

What's more, for anyone who likes a bit of sheen on their gum print,
this is the way to go. A one-coat gum print over this gum size glows
like a nice hand-rubbed varnish.

I'd never heard that gum prints aren't supposed to glow. I personally
think that's a silly rule, if there is such a rule. It seems to me that
people are always wanting to know how to give the gum prints some sheen.
It's been my experience that 2-3 layers of gum will shine, and I have
sometimes indulged in a gentle buffing with a soft (lintless) cloth, to
enhance the glow.
Katharine Thayer
Received on Tue May 24 12:30:43 2005