Re: Gum problem(s)

Christina,

I have put answers and comments below.

----- Original Message -----
From: "Christina Z. Anderson" <zphoto@montana.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, November 18, 2005 9:27 AM
Subject: Re: Gum problem(s)

> > I notice that the pigment/gum in the area outside the step tablet was
> > extremely soft and I removed it all by rubbing my finger as delicately
as
> > I
> > could. I assume I shouldn't do that in the future. One may say that's
very
> > good, you got 7 to 9 steps showing to which I would reply the separation
> > between those step is close to inexistant and we can hardly read the
> > number
> > or text because of the texture and staining.. If this was a delicate
> > flower
> > with lovely details, only my imagination could tell and this is
certainly
> > not what I was expecting but I also saw in my reading that this could be
> > helped by printing multiple time. Assuming the pigments don't get into
the
> > paper the texture would possibly improve as well.
> > Yves
>
> Yves,
> I, too, like Judy I think, can get easily 4-5 stops out of gum (unlike
salt
> printing, for instance, where one can get probably 10 stops).
>
> My exposures under UVBL are 6 minutes. Even 6 minutes is plenty. I am
> using diginegs.
> I, too, use Fabriano, but I size it.
>

It as become obvious that I need to do that.

> I am thinking my ratios are about like yours except I don't use photoflo,
> and i use tube pigment. Photoflo is a surfactant that might make your
> pigment sink into the paper more easily?

I also used a tube in other trials I made for comparison with very similar
effect. I saw somewhere that paint tube uses all kinds of stuff to help in
the dispersion of the pigments, possibly preservative and whatever else they
feel like is needed for production purposes. Later I intend to used only
"pure" pigments and no photoflo for sure. I'm just trying to get the process
working for me.

>
> If you are using analog negs, then I could maybe understand a 6 minute
> exposure, but 20 seems excessive with digital. One way to tell if the
> exposure is excessive is to leave the test strip soak for a day and brush
> it, and if it still doesn't clear, then you might have excessively exposed
> the emulsion or baked it on with the heat from the sun lamp.
>

I kind of decided at this time to use only a 21 step tablet to acquire an
intuitive feel of the various parameters involved and how they affect the
results. Also, I'm not expecting the top most 10-11 steps to print any thing
else then "pure" white. As for the 20 minutes well I would argue that it
depends a lot on your light source, the composition of its light and the
minimum and maximum optical density of the negative you're using be it
digital or whatever else. In my situation I could argue that I could use a
bit more time because I can see a tiny difference from step 1 to step 2 and
I assume overexposure would start to happen when these lower steps begin to
look all the same, yes/no???

> If your test strip is nicely exposed, without a lot of blocking at the
dark
> end, and your numbers are obliterated, then suspect the pigment has
entered
> the paper fibers and stained. Sizing will alleviate that.

This is going to be my next step and I already have questions regarding the
hardening of the gelatine but these can wait except one maybe.
I'd like to use ALUN because it is relatively non toxic compared to others
and if of course it doesn't affect the permanance of the piece in the long
run.

>
> BTW, the idea that the dichromate may, in fact, expose the layer at the
> bottom (I wouldn't have a clue if it did or not) probably stems from the
> observation that when you first soak your paper in the water face up, all
> the dichromate leaches out immediately. This only takes about a minute to
> happen, and then you can lift the print out of the water and watch the
> dichromate stream off. The layer is still perfectly intact. I have no
idea
> chemically why this is so--the chemists of the list can answer that
one--but
> I have observed sometimes in coating a paper with magenta that in my brush
> strokes the yellow of the dichromate brushes at the paper base and the
> pigment seems to be on top, so perhaps the dichromate is of a different
> weight or whatever the term is chemists use...mole...blah blah..
>

As I've writen elsewhere I have a big, very big problem with this theory. At
this time I don't see how it's even remotely possible but I could be dead
wrong on this.

> Happy gumming, keep it up, one more convert yea!!
> Chris
>

Thanks and my best regards
Yves
Received on Fri Nov 18 09:25:41 2005