On Nov 30, 2005, at 9:46 PM, Judy Seigel wrote:
>
> I didn't understand much of the discussion about printing clear gum
> arabic, partly because I didn't understand it, partly because I didn't
> think I needed to understand it, and partly from suffering from turkey
> poisoning. But I think one point needs to be made -- or repeated:
> Results with plain gum arabic and dichromate without pigment will NOT
> replicate results *with* the pigment. Or let me correct that to say, I
> doubt that they would or could.
Hi Judy,
Of course; and I think I've made that point several times, but perhaps
not clearly enough, in discussing all the different ways that pigment
can affect the tonal scale. My point about the unpigmented gum was to
emphasize that while the pigment does provide the tonal scale, it does
not participate in the reactions which constitute the response to
exposure, so unlike silver printing and many other photographic
processes, with gum you cannot draw a curve relating exposure to
*density of reaction product* to tonal scale. Hope that's clear as
unpigmented gum,
Katharine
Received on Thu Dec 1 07:59:34 2005
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