From: Judy Seigel (jseigel@panix.com)
Date: 11/12/01-07:08:07 PM Z
On Mon, 12 Nov 2001, Sandy King wrote:
> One obvious photochemical law that applies to gum printing is that
> the colloid we know as gum is most sensitive to radiation (and tans
> or hardens most) in a fairly narrow arrow band that appears to lie
> between 300-450 nanometers (and perhaps below 300 nanometers as well
> if we can use it). Regardless of other variables (how thick or thin
I think that "law" is as *loose* as the laws about taxes. I've made gums
by several sorts of bulbs & the particular spectrum of the bulb was NOT
overriding.
> you make the emulsion, or the pigment used, or the strength of the
> dichromate), it will be very difficult to make a gum print by
> exposing with a 50 watt bug-light. This law can be demonstrated
I suppose it would be equally difficult to make a gum print by 50 lights
of firefly, but don't think that's a very relevant "photo mechanical law."
J.
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