Re: printing gum on glass
When leafing glass, the usual cleaning regimen is to scrub with bon ami
cleaner, it won't scratch the glass and it gets everything and anything off.
I clean glass by washing in warm warder with Oxiclean. This works well.
From: Katharine Thayer [mailto:firstname.lastname@example.org]
Sent: Thursday, July 19, 2007 1:37 PM
Subject: Re: printing gum on glass
To address Judy's suggestion earlier about Christopher James' first
editiion: no, there's not a chapter on printing gum on glass per se
in the first edition. There's a section on printing gum on
"alternative surfaces, such as metal plates, stone, chalkboard slate,
glass, mica, vinyl or plastic" which addresses different ways to
introduce tooth to hard surfaces, including abrading the surface or
(more relevant to glass) subbing the surface with material that will
help the gum adhere. He doesn't (by my reading) repeat or deny any
myth about midtones and gum on glass, which by the way is a myth I've
never encountered. There is also a separate section about printing
on glass, not geared to gum especially, which gives Galina's method
of subbing the glass with gelatin.
It's no particular myth that gum doesn't adhere well to glass because
of the slick surface of the glass which offers no tooth for the gum
to hang onto, and as James indicates, the glass usually needs to be
treated in some way to increase the adhesion of the gum to the glass.
Some people use silane very effectively for a sub on glass for gum
printing. I have used a light dusting of fine pumice in acrylic
medium, for a sub to provide tooth for printing on glass.
The glass must be scrupulously clean; I find a final swash of 200-
proof alcohol works very well to remove every trace of whatever
cleaning material may be clinging to the surface after complete
rinsing; when it sheets cleanly off the glass without beading or
catching anywhere, you know the glass is clean. Then a sub, of
whatever works for you, and then expose the heck out of it (someone
told me this once a long long time ago and I didn't believe him, but
indeed, an extra-long exposure does increase the likelihood of
retaining the hardened gum on the glass) and then develop very very
gently, face up, with fingers crossed.
Or, as Marek suggests, expose from the back.