Re: Back-exposing on plastic (was: Re: Gum transfer

Katherine,

even if you don't read my posts, others may want to see them. You say the
following:

He just doesn't seem to get that you can't draw
any connection between number of steps printed and absolute print
density or tonal scale, because the density, tonal scale, and
contrast are a function of the emulsion and are different for every
emulsion.

I would correct you and say my position is and always was: "the exposure
response of every emultion is different"
Now you may not understand what I mean by "response". You know, when you
flash some (UV) light at an emultion and something happens, especially with
gum, that's a "response".

And when you say "I don't get it", may be it is just a question about of the
terms I use but again when you say this:
"the density, tonal scale, and contrast are a function of the emulsion"
take this nice emultion of yours and put in a (light tight) drawer for a
while (as long as you which) and then try to get something out of it, when
you take it of the drawer put it in water immediately of course, for 3 month
if you which and tell us all what kind of print you get. I apologise, I'm
sure you pretty well know that without exposure this exercise is just a
waiste of time. Now, how do you call this thing that happens when you leave
a emulsion in the dark for to long... You may get plenty of that though.

I totally agree with you that the response of a gum emulsion present some
features, characteristics or behaviour quite unique compared to most other
kinds of emultions. When you imply that density, tonal scale and contrast
have nothing to do with exposure as I read it above, I wonder who doesn't
understand what.

All this as to do with the claim I made often that anyone can put any tone
or density between a minimum (paper white) and a maximum or Dmax or darkest
tone on any kind of emulsion by simply and uniquely varying the exposure. If
you'd like me to be more specific I could say by varying the light energy we
submit our emulsion to. The problem as I see it, is that to vary the
exposure we usually use a negative but that as we all know, is not a
necessity either, there are other ways but it as its usefulness. Do you want
me to continue, hum, why not, I see a negative as a mean to vary the
exposure I give to a print and I use the term density again to reflect this
control I have over the exposure, maybe I should always say negative density
to eliminate any possible confusion, sorry I wont do it again.

Oh yes, I was trying to put any print density or any print tone I want
between the two possible extremes (paper white and the darkest possible
tone) that our specific gum emulsion can provide us. Well don't you go
playing tricks on me by changing something to the emulsion I studied
carefully. This time I wont even use a negative and to cut it short I
plotted the response of this same specific emulsion, don't you touch
anything now, and I know exactly how much, is it ok if I use exposure, let
say you said yes, so I know exactly what "print density" and indirectly what
tone I'll get with such and such exposure. If you still have doubt about all
this bs I challenge you any time any place, you can even submit your own
very difficult to print emulsion as long as it can produce a significative
print density above or below the color of the paper. Yes I said below, you
could try to trick me again by using a dark paper...

Is there something else you don't understand about what I'm not suppose to
understand, that sound funny don't you think. Well you may never read this,
it's a shame because I have great respect for you and of your work and I
appretiate a lot, the time, the knowledge and the efforts you have given me
in the past. It is not the first time we seem to misunderstand each other
and I don't really like what I just did by writing this but you basically
said you don't care what I can say so trying to reach you directly, well you
know better then me what would happen.

Regard
Yves

PS. Sorry Mark I left you out of this one.

----- Original Message -----
From: "Katharine Thayer" <kthayer@pacifier.com>
To: <alt-photo-process-l@usask.ca>
Sent: Thursday, May 04, 2006 5:01 PM
Subject: Re: Back-exposing on plastic (was: Re: Gum transfer

Mark, I saw and then somehow lost your followup. Sorry if I seemed
snappish a couple of posts ago. I don't read Yves's posts as a rule,
but did see some of the jeering directed my way in the quotes
attached to your responses, and I suppose some of my annoyance was a
response to that. He just doesn't seem to get that you can't draw
any connection between number of steps printed and absolute print
density or tonal scale, because the density, tonal scale, and
contrast are a function of the emulsion and are different for every
emulsion.

I just wanted to reply to your hope that one should be able to get a
good one-coat print by saying yes, certainly one can get a fairly
good "fully tonal" one-coat gum by balancing pigment concentration
and dichromate, and people have been doing that for quite a while (I
can get a fine one-coat in that sense with saturated ammonium
dichromate and the right pigment load) but like I keep saying,
there's fully tonal and then there's fully tonal. The only way I've
seen yet to get a fully tonal print in the sense of very subtle
gradations throughout a long scale, like a platinum or carbon print,
is by multiple printing, although I've seen some promise in the back-
exposure experiments. But I'll be delighted if you or Chris or
whoever can prove me wrong. That's what we're about here, to learn
from each other.
Katharine

On May 4, 2006, at 10:35 AM, Katharine Thayer wrote:

> Hi Mark,
> Thanks for your response, I wrote my last two before seeing this.
> Yes, pigment and dichromate are the main variables that affect
> contrast, although there is some evidence that the light source and
> even the gum brand may be implicated.
> Katharine
>
>
>
> On May 4, 2006, at 9:47 AM, Ender100@aol.com wrote:
>
>
>> Hi Katherine,
>>
>> Thanks for your response, I understand now what you were saying
>> regarding the tonalities with gum—that's what I thought you meant
>> originally, but my thick brain intervened.
>>
>> It would seem then that to get the "best" one print gum, then one
>> would have to play with some variables, and you gummists have
>> probably already done this.
>>
>> Starting with the best paper/sizing combination which prints
>> smoothly with longest tonal scale, adjust the following variables
>> until you get the longest scale on a stouffers, the highest Dmax,
>> and smoothest tones. Obviously there would be tradeoffs.
>>
>> 1. Adjust amount of dichromate higher for longer tonal scale
>> until no gain is seen.
>> 2. adjust amount of pigment higher for greater dmax until tonal
>> scale begins to fail.
>>
>> Other variables you could tweak?
>>
>>
>> In a message dated 5/4/06 10:31:00 AM, kthayer@pacifier.com writes:
>>
>>
>>
>>> Mark, I understand the theory here, but I also know gum, and I
>>> repeat
>>> that I have yet to see a one-coat gum that prints tones from dark to
>>> light, with all the tones in between. Maybe a better way of saying
>>> that is that given the kind of pigment load that you need to get the
>>> deepest DMax, the emulsion is going to be contrasty enough that
>>> there
>>> will be gaps between the tones rather than a smooth gradation.
>>> Surely you can see for yourself that Chris's gum print is jumpier in
>>> tone than the platinum print; throughout the portion of the scale
>>> that they both print, there are gradations of tone in the platinum
>>> print that just aren't there in the gum print. So while it seems
>>> theoretically to make sense to say that gum should print all the
>>> little tones between the DMax and the DMin, the fact is that it
>>> doesn't, not in one coat. Like I keep saying, I'm ready to be
>>> pleasantly surprised, and this is what I'm aiming for with the back-
>>> exposure experiments, but I have yet to see a one-coat gum that can
>>> print a delicate gradation of tones throughout a full tonal scale.
>>> Yes, of course, a one-coat gum can print a rather contrasty
>>> approximation of a fully tonal scale, I would have thought that went
>>> without saying, but like I say, there are "fully tonal" scales and
>>> then there are fully tonal scales.
>>>
>>> I do think Chris could get a better approximation to the smooth
>>> tonal
>>> gradation of the platinum by using less pigment, but then the
>>> question is whether you can get the DMax. Maybe, maybe not. And
>>> this
>>> is the struggle always with gum, as Sandy and Terry and many others
>>> have pointed out. More pigment means deeper DMax but more contrast,
>>> less pigment means more subtle tonal gradation but less DMax.
>>> This is
>>> the eternal equation of gum; it's got little to do with curves. Yes,
>>> if you've got a really bad curve to start with, as Chris has here,
>>> you can improve it, But you can't improve it beyond the limitations
>>> of the particular emulsion you're using, which I suspect Chris may
>>> have demonstrated in the prints she posted.
>>> Katharine=
>>>
>>
>>
>>
>>
>>
>>
>> Best Wishes,
>> Mark Nelson
>> Precision Digital Negatives--The Book
>> PDNPrint Forum at Yahoo Groups
>> www.MarkINelsonPhoto.com
>>
>>
>>
>
>
Received on 05/04/06-04:33:38 PM Z