From: Joe Smigiel (jsmigiel@KVCC.EDU)
Date: 04/02/02-10:07:37 PM Z
I suspect the actual color of the ink is of little consequence in the effect. If the particular ink/stain is a window to UV, then as Jeffrey suggests, the sensitizer will be affected regardless of the color of the ink. When I tested the absorption spectra of ammonium dichromate a few years ago it had very little absorption in the visible wavelengths. As a result, I would not expect any color to affect it. I did test the spectral negatives and found the results poor compared to conventional negatives and inkjet negatives produced using Cone piezography quadtone inks (carbon based?). As I recall, I tested the spectral negatives with cyanotype and did not get sufficient contrast.
So, I would presume the actual sensitizer makes a great deal of difference. Most of the respondants are talking about Platinum processes which may have an entirely different sensitivity in visible spectrum than dichromates. Does anyone know for sure, or are we all making the assumption that if a sensitizer is UV-sensitive, then it will also be sensitive to visual wavelengths?
Perhaps yellow-green pyro works because platinum sensitivity extends functionally into the longer violet wavelengths???
Another point to consider is that the 0-71-71-0 combination from one inkset will not match that produced by another manufacturer or model printer.
"Your mileage may vary".
Joe
<<< jeffrey.d.mathias@worldnet.att.net 4/ 2 9:26p >>>
Katharine Thayer wrote:
> I've been puzzling about spectral density and hope there's someone here
> with enough knowledge about the physics and psychology of the
> electromagnetic spectrum to help me understand the things I'm puzzling
> over.
A word of caution. It is important to know the spectral transmission
characteristics of the particular inks used. One can theorize all they
want, but the results will be based on the specific ink(s) used. A
particular color may be useless if it does not transmit or block the
particular wavelengths (UV or otherwise) that the sensitizer is
sensitive to. A particular ink color or type may have very unexpected
UV characteristics.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
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