Re: Sensitized Gum paper

Carson Graves x4692 3NE (carson@zama.hq.ileaf.com)
Wed, 15 Jun 94 12:41:29 EDT

> From: "Olivo Miotto, DBS/It- @VAR - DTN 787-8444 15-Jun-1994 1715" <miotto@pavone.enet.dec.com>
> Hi-
>
> just a couple of quick questions on making gum coated paper:
>
> 1) Is it right that coated paper lasts a long time in the freezer? I've done a
> little test over a week or so, and it seemed all right- I wonder if anybody
> has done some more extensive tests. Being able to prepare the paper in "bulk"
> in advance would be a great advantage.
>

The problem you want to avoid is humidity. As Henry Wilhelm discovered some
years ago, some brands of fridges maintain a low humidity in their freezing
compartments and others don't. Another issue is that once a dichromate
emulsion receives any exposure that exposure is "recorded" i.e. can
show up as fog. I have also been given to understand that the hardening
of the emulsion when exposed to light continues even after the exposure
is stopped (which is why you want to "develop" the print immediately
after exposure).

Taking all this into consideration, I would say that *if* you can maintain
complete light safeness and a low humidity during storage you will
probably be all right. OTOH, I always had best results exposing as soon
as the emulsion was dry.

> 2) Do I remember correctly somebody saying that you can brush the sensitizer
> on the paper first and then spray on the gum/pigment later? Don't the two
> suffer from not being mixed ahead? Does the sensitizer still manage to combine
> with the gum? (Of course, the spray method would be advantageous for
> smoothness, and separating the two solutions would mean less wastage when
> using non-artist airbrushes.)

I can't imagine how this would work, but I've never tried it. I do want
to say that you should *never* attempt to airbrush the dichromate
either alone or in combination with the pigment/colloid w/o major
safeguards such as a fume hood and a respirator. I know that this isn't
what you say you want to do, but I thought a warning was appropriate
anyway.

Carson Graves
carson@ileaf.com

>
> I appreciate any feedback
> Olivo
>