From: Christina Z. Anderson (zphoto@montana.net)
Date: 06/29/03-01:09:54 PM Z
Katharine,
You are so right. Duh. I frequently miss the obvious. But I figured
since there were more little steps printed, even if stain, that equated to
more exposure. So I just went back and printed three more test strips of
am, pot and sod WITH pigment now, and there are, in fact, more steps
printed, the numbers are darker and sharper and clearer and punchier with
the am di. Sod is faster than pot, which didn't even print a maximum black
at the 3 minute mark with q. pink. It looks, by eyeballing (very inexact)
that I have at least 2 clear steps more with am di than sod di. On that 21
step Stouffers. I'll go try it again with a different pigment and longer
exposure and see what other results happen and if I can keep repeating
myself.
I have also been practicing the method (aside from Berger) of coating
the paper with a saturated solution of dichromate alone, and then coating
later with pigment and gum on top of the dried, sensitized paper. You have
to add water to thin the pigment gum, as much water as you would dichromate
in your usual mix. I'm not sure why this has benefits...what I was testing
is speed, because they said in old books that the speed was greatly
increased by this method, to equate that of a platinum print. Go figure. I
don't find gum slow by any stretch of the imagination, exposure wise.
Anyway, what I do see with my first few tests is less grainy
highlights, sharper detail, and more contrast. I remember doing this
several months ago and finding it had better contrast, too. I'll keep
printing and see if I can keep repeating this outcome, but I have no idea
why this would be the case unless, as someone previously said on the list
(you or Judy) it may be the dichromate is at the bottom of the layer of
pigmented gum and hardens from the bottom up (?) or maybe the dichromate
when mixed into the pigment and gum makes it harden into microscopic
globules which equates to grain by our eyes. I'm just throwing this all out
there and thinking aloud, so maybe all of this is totally stupid, but for
what it is worth, that is what I am doing. Of course, if you are doing
multiple gums, this would only work on the first layer, unless doing the
Berger method, but even with that I dichromated my next two layers as per
usual.
And, as Judy said, this isn't standard practice today, so there must be
a reason it isn't used regularly anymore..perhaps being a waste of an extra
coating step you have to do.
Chris
----- Original Message -----
From: <kthayer@pacifier.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, June 29, 2003 10:25 AM
Subject: Re: lemon juice and gum printing
> > Hi Keith,
> > One thing I did today, too was to do side by side exposures of am,
> > pot
> > and sod di to see if there was a speed dif. I swear, am di is really
> > fast! It gives the clearest, sharpest steps of all three dichromates, is
> > the speediest, and sod is not much different than pot. I did this test
> > with NO pigment, just side by side straight dichromate. Then I cleared
> > to see what remained, and the am di was the only one that printed the
> > numbers and the words and the steps of the tablet.
>
> Hi Chris and all,
> I think what you're demonstrating here isn't how the three dichromates
> print in normal gum printing so much as you're providing support for the
> idea that ammonium dichromate "stains" (meaning dichromate staining, not
> pigment staining) more than the other dichromates, which I haven't
> observed myself but others have reported. If there's no pigment in the
> coating and you still see the numbers, words, and steps of the tablet
> after the print has been cleared, then you've got dichromate stain, which
> in my experience generally results from overexposure.It may be that people
> want to print with dichromate stain rather than with pigment, as in your
> historical example, but we should be clear that that's something different
> from the usual printing practice.
> kt
>
>
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