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Re: chrome alum
Title: Re: chrome alum
Sandy King (or anyone else in the know), a while back you said you
usually use chrome alum for hardener, sometimes potassium alum, too.
mentioned mixing 2 g of chrome alum (the purple stuff) per 1000
gelatin solution. This is about 1/2 tsp. How much
*gelatin* do you use in
your 1000 ml--my formula calls for 2 tsp Knox gelatin, does yours,
I'm starting to work with tiles and glass to
get liquid emulsion to
stick, and a student wants to try to sub glass with the chrome alum
for gum; she tried it already with varnish and a mild sanding and the
totally came off. She was inspired by my telling her a while
Sarah Van Keuren's students doing gum on glass. Short of a
we're going to keep trying.
Others have already addressed part of your
message about chrome alum, but not as I recall the part about how much
gelatin should be used per 1000ml of solution.
First, a couple of points. My use is almost
certainly different from yours as I size paper to serve as final
supports for carbon transfer prints, not for gum printing. Second, as
Don Bryant's copy of part of a previous message I posted to the list
on this topic indicates, I size differently depending on whether I am
working with the single or double transfer method in carbon
For my single transfer papers, which would
probably work well for gum printing as well, I use about a 3% gelatin
solution, that is, about 30g of gelatin dissolved in 1000ml of water.
To this I add 2-3g of chrome alum, which I first dissolve in about
50ml of warm water. I often also add a few grams of corn starch to the
sizing solution, the purpose of which is to give a more matte look to
the borders of the final print.
I coat with this sequence:
1. Soak the paper in warm water for about 10
2. Squeegee the paper to a flat level
3. Wipe off the excess water with a clean
4. Apply the coating with a brush, allowing about
100ml of solution per 22X29" sheet of paper. If air bubbles form
during coating, mist with alcohol.
5. Allow the gelatin to set.
6. Dry by either hanging from a line or by
placing on a drying rack.
One coating usually suffices for my application
but very thick and rough paper may require an additional layer of
One could substitute 2-3ml of either formaline or
glyoxal in place of the chrome alum. I don't use formaline because my
coating is done indoors and the fumes are impossible to live with and
don't use glyoxal because it yellows my papers. Papers sized with
chrome alum should be set aside for several days before use because
the hardening takes longer than with formaline and