Re: outdoor gum demo
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.
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