Gum Curves, new topic please????

Good morning,

I'm late in replying to a post of yours Yves, so forgive. I have to spend
too much time wading through political crap, which to me is anaethema to the
list. I get enough of it on the news. My parents raised me not to talk
about religion and politics in mixed company--where does it get us? My
mother was an aetheist, my father a believer, hence the reason to keep the
peace. AND, I took after my father in case anyone gives a rat's ass.

SO I thought I would open controversy back into photography and give people
something more "alt" to argue about. Gees.

In reference to curves, I thought of summing it up this way, Yves:

"No curve can transcend the limits of the process, but sometimes what is
termed "the limits of the process" can, in fact, just be an improper curve."

Whether exhibited in an improper density range of an analog negative or an
improperly formulated digital negative, I think this has forever been true
with gum.

All a perfect digital curve will do for you in gum is make it a hell of a
lot easier to get a good print--you find your standard printing time to
harden the gum, your color negative that you will use to hold back enough
light to give you paper white, and then the curve to give you the range of
tones from black to white. I find then that gum becomes very predictable
and not the capricious process it is always termed.

NOW, all of that said, people have been getting gorgeous gum prints for
centuries without a perfect digital curve, using analog negatives, paper
negatives, imagesetter negs, lith negs, toilet paper, ...I was just copy
sliding Bea Nettles' quik prints from Flamingo in the Dark and I STILL find
her work evocative and gorgeous and all of it was done before a home output
digital neg existed. My whole thesis, for instance, was done pre-PDN, but I
did use a curve. But what I found when I went back and
reprinted those same images with a custom derived curve suited to each color
was WOW, the image was better, more accurately color balanced to
the original, you name it. It was a revelation.

BUT, if all I taught in my alt class was how to produce perfect tricolor
gums, what's the point?? That is only a starting point to understanding the
gum process, and then springboarding off of that to produce imperfect
prints, so to speak, just as nowadays you can see the proliferation of
scratched negatives, blur, dark prints, and all those experimental kinds of
things that people are doing with analog photography. I feel that will be
the style of the early 21st century--this beautiful darkness.

I have just sent Loris Medici offlist (my website STILL under construction)
an image I have been working on so in time he will post it. Seems Sandy is
too busy talking politics to send me a carbon print (that was a big HINT
Sandy) so I took it upon myself to one-up Sandy--I have a large platinum
print of a New Orleans subject called Mobile Home. I scanned said print.
That is why only part of the image is there because it is too big to fit on
my flatbed. Unfortunately, there is no comparison between carbon processes,
the original reason for the experiment. The original quest was to see if a
one coat gum could in fact rival the detail and tonal range of a carbon
transfer print, etc. etc.

This is my explanation for the image:

ALL images have been scanned and not dinked with at all. No sharpening, no
tweaking, nothing. As is.

I felt comparing gum to a platinum print with its gorgeous tonality and
smooth transition would be the ultimate insult to gum, even more than
carbon.

What I then proceeded to do was take 1 g. carbon powdered pigment to 100ml
of gum--Dave Rose's formula, and do a print. Too weak. Then I upped it to
2g. Still too weak. Then I upped it to 3g. Fine. Then I developed a
curve based on 3g carbon powdered pigment to 100ml gum.

I have labeled each image on the composite so it should be explanatory.

I also included on there the image of gum printed on unhardened gelatin.
You all be the judge.

I had to redo the curve several times to adjust for increased pigment load
and the fact that with increased pigment load I had to expose longer--I
ended up with a 9 minute UVBL exposure for a one coat carbon.

What I proved to myself is that one can certainly get a fully tonal gum
print with dmax in one coat. Will it rival a platinum or carbon (if I could
actually SEE a carbon)? Probably not. Is it better to do a fully tonal
print in more than one coat? Probably easier. Do you need to expose from
the back to keep the layer adhered to the paper and fully tonal? Why? If
you expose long enough to harden the layer to the paper base and curve
properly so at that time you still have highlights, it should be fine. The
need for a curve and a perfectly sized and hardened paper goes without
saying and should be apparent in the comparison.

Open the floodgates...
Chris

----- Original Message -----
From: "Yves Gauvreau" <gauvreau-yves@sympatico.ca>
To: <alt-photo-process-l@usask.ca>
Sent: Saturday, April 29, 2006 6:32 AM
Subject: Re: Back-exposing on plastic (was: Re: Gum transfer

Mark,

thanks you very much, you have summurised what I have been saying all along
from my first message here on this list about gum. Gum is just another
photographic process, nothing esoteric about it and just like another
process, gum as its features and true these makes gum a distinctive process
but still a photographic process.

Regards
Yves

  ----- Original Message -----
  From: Ender100@aol.com
  To: alt-photo-process-l@usask.ca
  Sent: Friday, April 28, 2006 1:48 PM
  Subject: Re: Back-exposing on plastic (was: Re: Gum transfer

  Yves,

  The gum variables can be modified to change the Exposure Scale of the
printing. If you first adjust the density range of the negative prior to
applying a curve, then you will get the maximum from the gum print—then the
curve is only used to adjust the relative tonalities between DMax and Paper
White. The adjustment of the density range of the negative is pretty
important for gum, since it has a shorter exposure scale than many other
processes and requires a lower density range negative. Doing this is one
(just one) reason why Chris Anderson is having so much success with her tri
color gum thingies.

  An example might be making a negative with an Epson 2200 where the UV
transmission density of a negative using all inks can be over log 4.0—so if
you need a negative to match an exposure scale of gum at let's say log 1.2,
then you have a mismatch of 4.0 - 1.2 or log 2.8 TOO much density in the
negative that the curve has to adjust for—that is over 7 stops! This is why
you often see people using curves where the endpoint has been moved to
reduce the density so the highlights won't blow out... unfotrunately for
every point that you move that endpoint, you lose that many tones in the
negative. You can actually use this to calculate exactly how many tones
will be lost.

  Best Wishes,
  Mark Nelson
  Precision Digital Negatives--The Book
  PDNPrint Forum at Yahoo Groups
  www.MarkINelsonPhoto.com

  In a message dated 4/28/06 10:43:12 AM, gauvreau-yves@sympatico.ca writes:

    Katharine,

    my first reply on this topic was probably the cause of the
misunderstanding,
    when I read it back now I see what you mean. With the last one I thought
I
    made all this as clear as I can but I'll try again. If whatever you do
back
    exposing your print fails to give you a satisfying tonal "delicacy" as
you
    put it, may be applying a different curve would help.

    If I understand normaly exposed gum printing (front exposed) you can
control
    the distribution of pigment (tonal "delicacy") by the various usual
means
    including % gum, % pigment, % dichromate, thickness of emultion,
    exposure(s), development and physical manipulations, etc. With back
    exposure, it seems only one exposure can be done and all I'm saying is
that
    beside all the usual controls you have the possibility to change the
    negative density (distribution) by applying some curve. Can you control
    every thing with some curve, the answer is simple no. The reason for
this is
    that a couple variables of the gum process are totally independent of
    exposure (negative densities), the pigment load, as you call it, is one
of
    these, development and physical manipulations are other mean by which
you
    can alter the tonal distribution, in the limit you can scrape it all off
    (the emultion).

    I would certainly claim that if you maintain every variables fix ie. you
    don't change anything from print to print except the curve applied to
the
    negative, you can basically obtain any tone you want between the Dmax
and
    the Dmin of the print. Obviously, this fix variable gum print must show
    something usable to begin with.

    Regards
    Yves
Received on Mon May 1 00:05:43 2006