Re: Using alum to size for gum

Luis Nadeau (nadeaul@nbnet.nb.ca)
Tue, 25 Jul 1995 10:56:38 -0300

>Dan, I trust you destructively distill those ants in clam
>chowder.
>
>As for alum in gum size, I, too, have read warnings against it in RECENT
>books. But just about every pictorialist/early-gum how-to I've come
>across, if it added gelatine size, called for alum to harden it. (Puyo
>decisively dismissed the need for added size, though he's the only early
>source I think of who actually mentioned formaldehyde in case you did size
>-- that is, he called for "formol", which is NOT in my French dictionary,
>but I take it for formaldehyde.) The alum, BTW, was usually added to the
^^^^^^^^^^^^^^^^^^
it is

>gelatine, not used as a separate bath. Are those prints OK? The early
>gums I saw were, but were they alummed??
>
>On Tue, 25 Jul 1995, Dan Shapiro wrote:
>> If the point of sizing is to make paper fibers resistant to staining and
>> expansion/shrinkage with water, could you, in principle, size paper
>> using dichromated gelatine, exposed without a negative?
>
>That's pretty ingenious, though it might stain, or would take a long ^

Perhaps ingenious, but certainly not new. It was used over a hundred years
ago to produce a sub-coat for the collotype process.

Much of the resulting stain can be removed with various published methods
although a complete removal may require the dangerous use of sulfuric acid.
All methods seem to soften gelatin to a point.

Luis Nadeau
NADEAUL@NBNET.NB.CA
Fredericton, New Brunswick, Canada

>soak to remove the stain, and, if the purpose is to
>avoid noxious formaldehyde, how much improvement would extra dichromate be?
>Why don't you try it, though?
>
>Incidentally, the pictorialists were wont to expose a coat of just gum and
>dichromate without pigment (or only a tiny amount) to give an allover
>tone to the paper.
>
>
>> My intuition is telling me that quality/predictability will be enhanced
>> if we can reduce the number of chemical agents involved in making gum
>> prints.>
>
>Maybe, maybe not. The gelatine in dichromate would be different from the
>gum in dichromate.
>
>You're an optimist, though, thinking you can outwit "it."
>
>Judy