Re: Why multiple exposure (was Re: (Gum) Tonal scale)

On Mon, 28 Nov 2005, Yves Gauvreau wrote:

> I made some test of my own and I got about 6 to 8 steps (Stouffer 21 steps)
> dependent (as expected) on the gum pigment mix I used. I didn't measure the
> densities but I think everyone knows each step correspond to approximately

CUT....

> So I guess my real question then is how come all the fuss about multiple
> exposure that many seem to favor for gum prints???

Yves, I think the intervening replies have addressed your question, but
permit me to add my own thoughts as I read the above...

If you are getting 6 to 8 steps in a gum print with one coat and a
tonal range that satisfies you pictorially, I suspect you are wasting your
time on this list. You could be out in the world walking on water-- and
running workshops.

My other thought as I kept on reading was that when I run the world no one
who hasn't done, oh, say 50 gum tests on their own (perhaps using the "gum
entry exercise" I used to give classes -- and could swear I put somewhere
in P-F, about which more in a moment) is NOT allowed to discuss "theory"
and "principles" here, or anywhere. That's because you get into so many
abstruse issues that simply do not apply, but hold over from silver
gelatin, that the only recourse is to retreat in dismay.

It is THESE discussions (seems to me) that make gum seem so queer, so
whimsical, so devilishly complex. In the actual practice, if you start
simple, and do NOT expect "rules" for "best" or "correct" or "right"
print, and dismiss all theory in advance, it's quite simple.

Here's the entry exercise:

Mix a standard emulsion, say a pea sized lump of a good simple pigment
(thalo blue is usually trouble free) in a good brand, with 30 drops gum
arabic, 15 drops concentrated am di & 15 drops water. Coat a piece of
unsized unshrunk Rives BFK (or paper of your choice, that you know is
"good for gum") and when dry cut into 3 strips. Expose all strips the
same UNDER A 21-STEP (NOT a random-density pictorial negative) say 3
minutes in your normal UV light. Develop first section for 20 minutes, 2nd
section for 3 hours, and 3rd section for 18 hours or overnight.

Now study the results and COMPARE number of steps, density, smoothness of
tone, color, delicacy of the numbers printed, and whatever. This should
give an outline of the (what is it, see saw? balance? correlation?) of
exposure and development which underpins the medium.

Your first test may have too much or too little exposure, or too much,too
little pigment, etc... So you adjust. But a few rounds of this exercise
show the principles and the rest will probably fall into place.

You can do a test like this comparing sized, unsized paper, and other
variables but total confusion should vanish...

As for those three-coat prints, again that's a convention but with a
rationale -- in the early days, gum prints were usually monochrome black,
even with several coats. The tradition was, begin with (say), a warm black
fairly light on pigment for a long exposure to fill in your highlights --
tho shadows will of course be too light. Next coat would be more pigment
less exposure and a neutral black, for neutral midtones. Last coat, cool
black (add blue) for cool shadows, more pigment, less exposure (so you
don't fill in those highlights).

Or, you could do cool highlights, warm shadows. Whatever. Check Paul
Anderson in his Pictorial Photography book, ca. 1935. I knew a guy who
did these so precisesly folks who didn't know gum took the prints for
platinum. (Of course they were idiots, but... aren't we all out of our
depth?)

Judy
Received on Mon Nov 28 22:28:29 2005