Re: (Gum) Tonal scale

Katherine,

You know the difficulties english gives me and I'd like to know if I read
you correctly this time.

The way I read it, you basically say that because the stuff we put on the
paper in gum prints is different then what is used in carbon, cyanotype,
kalitype, platinum, silver, tempera and probably most other types of prints
that we can't establish a quantitative or even a qualitative relation
between a certain given amount of light and a tone on the paper using a
measure like the optical density of this tone.

Is what I said here essentially the same as what you have been saying all
along???

Regards
Yves

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, December 03, 2005 1:57 PM
Subject: Re: (Gum) Tonal scale

>
> On Dec 1, 2005, at 11:02 PM, Judy Seigel wrote:
>
> >
> > On Thu, 1 Dec 2005, Katharine Thayer wrote:
> >
> >> ... 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.
> >
> > Actually this calls to mind an expression I've used in trying to
> > explain the process -- I say the action is the gum, dichromate, etc,
> > and "the pigment is just along for the ride." But in fact, it occurs
> > to me that the character of the passenger can make a large difference
> > also -- if he weighs 300 pounds, if he keeps opening all the windows,
> > if he throws rocks at the bicycles passing by, etc. (Or "she," of
> > course.) That is, we do know that the particular pigment affects
> > behavior -- even if just its opacity.
>
> Which is what I keep saying. Or maybe you're just writing to say you
> agree with me, but every time I agree with you, you write back to agree
> with me again, which makes me think that you think we are debating
> opposite sides of an issue. My whole point is that tonal scale is a
> function of pigment and pigment concentration, (mainly, but along with
> a host of other things) and so if everything else is held constant,
> every pigment and every concentration of that pigment will give a
> different tonal scale. Yes, pigment affects behavior, very very much,
> that's exactly what I'm saying.
>
> My whole point, and my only point, throughout this discussion, is that
> the relationship between tonal scale (since it is made of pigment which
> does not participate in the reaction) and response to exposure, (since
> it is the production of transparent crosslinked gum) is an indirect
> and largely unknown (in a quantifiable sense) relationship, and so
> can't be graphed to read tone from density of crosslinked gum, as
> someone wanted it to. How many times would I have to say that, I
> wonder, before people started understanding what I'm saying.
> Katharine
Received on Sat Dec 3 14:14:53 2005