From: Joe Smigiel (jsmigiel@kvcc.edu)
Date: 06/29/03-05:20:44 PM Z
Chris & Katherine,
I think what is being demonstrated here may be underexposure (or speed) of the Na & K flavors rather than any dichromate stain. The fact that numbers and letters remain with the ammonium exposure indicates that a chromium image, not a non-image stain, has resulted using that salt. A "stain" IMO would be a general overall fog and not an image as you describe here. The step wedge has blocked exposure in the dense areas (numbers) and formed a reversed image of them if I'm reading this correctly. That's an image.
Also, I'm not sure what you mean when you say you cleared the print. Was this plain water or something like potassium metabisulphite? Water would leave the image/stain intact (assuming sufficient exposure) while the latter would wipe out any chromium image or stain.
Joe
>>> kthayer@pacifier.com 06/29/03 11:30 AM >>>
> Hi Keith,
> One thing I did today, too was to do side by side exposures of am,
> pot
> and sod di to see if there was a speed dif. I swear, am di is really
> fast! It gives the clearest, sharpest steps of all three dichromates, is
> the speediest, and sod is not much different than pot. I did this test
> with NO pigment, just side by side straight dichromate. Then I cleared
> to see what remained, and the am di was the only one that printed the
> numbers and the words and the steps of the tablet.
Hi Chris and all,
I think what you're demonstrating here isn't how the three dichromates
print in normal gum printing so much as you're providing support for the
idea that ammonium dichromate "stains" (meaning dichromate staining, not
pigment staining) more than the other dichromates, which I haven't
observed myself but others have reported. If there's no pigment in the
coating and you still see the numbers, words, and steps of the tablet
after the print has been cleared, then you've got dichromate stain, which
in my experience generally results from overexposure.It may be that people
want to print with dichromate stain rather than with pigment, as in your
historical example, but we should be clear that that's something different
from the usual printing practice.
kt
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