U of S | Mailing List Archive | alt-photo-process-l | Re: outdoor gum demo

Re: outdoor gum demo

I have had success with storing prepared sensitive gum paper for days
interleaved in a sketchbook in the fridge. Take a tiny "Dorm fridge"
with you to keep the emulsion cold.


On Wed, Apr 15, 2009 at 7:09 PM, Katharine Thayer <kthayer@pacifier.com> wrote:
> Hi Laura,
> This sounds like fun, and it also sounds like you have the right attitude to
> roll with whatever  punches the unusual situation throws you and just enjoy
> the experience.
> First, the dark reaction is largely a function of humidity; if the air is
> quite humid (like 70% or more) I'd be leery of coating the paper even an
> hour ahead of time; if it's really dry (like 20-30% or less) you might be
> able to get away with coating the night before, but I think I'd want to do a
> test ahead of time, in similar conditions, to be sure.
> Then, ambient light during coating.  During the five years I lived at the
> beach, I coated my paper next to a solid wall of glass 12 feet high, and
> never got fogging from the ambient light.   The windows faced north and the
> house was surrounded with pine trees, so there was no direct sunlight,
> except that during part of the summer, just before sunset a stray sunbeam
> could sometimes find its way through the pine trees and through a little
> window on the west side of the studio, and expose the paper as I was coating
> it,  in the shape of the window frame.  You definitely don't want sunlight
> shining on the coating, even in the very late afternoon.
> I always dried the coating immediately (with a hair dryer) and exposed
> immediately; I wouldn't recommend keeping coated paper around in reflected
> daylight for very long at all.  One time when I noticed a fingerprint on the
> negative just as I was putting it on the coated and dried paper,  I went off
> to the darkroom to find the negative cleaner stuff, and when I came back a
> few minutes later, the ambient light coming in through the glass had exposed
> the image, with the negative just sitting lightly on top of the paper.   I'm
> not sure how Keith manages to dry his coated paper outside without fogging
> it, but then Keith is a wizard, and also maybe it has something to do with
> dichromate; I use saturated ammonium dichromate which would fog faster than
> a less concentrated dichromate.  So that's another thing to consider.  Since
> the sun exposes so fast, you can easily use a less concentrated dichromate
> and still get fast exposures in the sunshine, and have less risk of the
> coated paper fogging while waiting.   My exposures in the sun for gum are
> less than a minute with 27% dichromate.
> Forget the yellow tent.  Haven't we just finished a discussion where we
> agreed (I certainly thought so) that the idea that the visible color of a
> thing is related to the UV-blocking capability is, well, to quote someone
> else's phrase,  "a nonsense" ? That goes for the pigments used to dye
> material for a tent  as well as for the inks in an inkjet printer.  A tent
> might be useful if you don't have shade where you're going to be, but I
> wouldn't worry much about the color of it.
> If it were my project, and if your climate is quite dry, I'd coat and dry
> the papers at home the night before, then put them in a big black envelope,
> like the black plastic envelope that came with a package of big photopaper,
> or even a garbage bag or something, when you carry them to the event, then
> keep the bag out of direct sunlight so the coated papers don't get hot.
> If your climate is damp, (sorry, I'm quite ignorant of what it's like in
> Iceland in May) then you'll need to worry about the dark reaction, which
> means you'll need to consider a way to coat and dry fairly close to time of
> exposure.  So the climate will have a lot to do with the decisions you make.
> Hope any of that is useful, good luck!
> Katharine
> On Apr 15, 2009, at 1:26 PM, Laura V wrote:
>> This is all very interesting...I've never "tested" the amount of ambient
>> light I can get away with, since the exposure unit I use is in a dark room,
>> I always coat in there, under safe light since I assumed using flourescents
>> would be bad.
>> Loris, is the idea of the yellow tent to create a safe light situation?
>> Keith, could the fact that the coated print you found was already exposed
>> make a difference to one that was just coated and not exposed?
>> At any rate, I think I need some sort of tent to create shade, and also
>> because the weather is unpredictable, it could even rain (and I guess that
>> will make exposure difficult!) And Loris, I'm  totally fine with looking
>> awkward/ridiculous...it happens often :)
>> Laura