Re: Dark reaction
Judy wrote: your comment makes me think that there's really no such thing as "fluorescent lights" -- but probably 10 different kinds (eg. black light fluorescents, & some other kind my neighbor was using (as I recall "blacklight blue"), plus plain vanilla "regular" fluorescents, and probably every few years a change in "state of the art" -- In my own experience, not only differences in the actual colors of the light and the starters, but differences in the bulbs as well.True, but commercial fluorescents of all kinds start with a low-pressure mercury arc, which creates predominantly UV energy, which the phosphors on the inside of the envelope absorb and re-radiate at visible wavelengths. For blue-sensitive and orthochromatic (blue + green) materials, the actinic light from fluorescent lights is mostly the "leakage" UV -- the UV that is not absorbed by the phosphors -- rather than the visible light output. There is a fair amount of this "leakage UV" from all fluorescents, although there is certainly some variation. However I do know that gum really is so flexible that that level of "fogging" could have been incorporated into our procedure... that is, just a somewhat longer soak. (We coated by the fluorescent light but had a drying closet with only a red safe light.) I concur. What "dichromated gelatine" process do you use Etienne? What's it called for short?The carbon process and gelatin-based oil printing are the two most well-known. I have also done direct carbon, coating a more or less standard carbon emulsion onto a grass or plastic substrate and exposing through the substrate, and a dichromate-based dye imbibition process similar to dye transfer (DT hardens the matrix-film gelatin with the reaction byproducts of the development of the silver image -- I've done it directly with dichromate). As long as I'm on the subject, anyone who wants knock-down gorgeous B&W images (not just B&W -- monochrome of any hue) in the tradition of the best non-alt processes may want to try single-color dye-transfer printing. It was a well-kept secret back in the heyday of DT (which was most commonly used to make stunning color prints). Jim Browning of Digital Mask is (or at least was, a few years ago) supplying the necessary materials to practice the process. Or, you can make your own according to his most excellent instructions: http://www.dyetransfer.org/images/DyeTran.pdf The gelatin-dichromate dye imbibition process obviates the need for matrix film and hardening developer, but the mordanted final substrate and the dyes are still required. Best regards, etienne
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