Re: Gum hardening: top down experiment good image

It took me two day to sort thing out a bit. I have repeated the experiments
with the HP transparency coated on the emulsion side with the thick gum
mixture. I tried exposure form the back from about 5 to 30 minuts and every
time the result was the same. I could see the image developing, I would take
it out of water and literally see it melting in front of me. Even lying
flat. It looked like gelatine meting, kind of losing shape, becoming softer
and ending up with a puddle of pigmented gum (remember the Indiana Jones
movie?). After removing all the gum from the transparency I noticed a very
nice tan image embeded in the transparency coating. Kind of like a very thin
of pyro stain. All the details vere there if you held it to the ligh just
so. So something was happening with htis transparency coating that was
messing up with my experiments.

Next logical thing was to put the gum on the uncoated side. I coated a
couple sheets, exposed through the back They all developed by dissolving the
unhardened gum from the top, revealing a continuous tome image beneath. The
image was rather robust, with no tendency to flake, slide off or anything.
Did I mention that on some of the sheets I removed the coating by soaking in
chlorox and scrubbing with a brush.

It is so amazing how easy it was to make a good image. My coating was very
heavily pigmented and thick. I could barely see through it looking directly
into a 50W light bulb.
Same coating exposed from the front simply flaked away. Same emulsion coated
on paper and exposed in the usual way for 15 minutes mosty flaked off with
a very contrasty result that did not resemble the original image to a great
extent.

I am really excited about making prints on glass and perhaps transfer to
paper.
I do not have a web page, but I scanned the transpareny in my flat bed
scanner (not in the transparency mode, it is just a reflective scanner).
Katharine maybe you can add it to you page or somebody else. I could put it
on one of the free web site, but I will not have time to mess with it until
the weekend.

All this most likely does not relate to regular practice of gum printing
wityh very thin layers, where I think enough light is passed through to
harden the entire layer (pehaps a crosslinking is a better term) and then
during the development phase wash away the gum and pigment in proportion to
the crosslinking. Paper does interact as well and I see it soaking
dichromate from the gum solution on the first coat, just like a lot of
people have observed. Oddly enough this does not happen on subsequent coats
if you do multicoat gums.

Experimentation rules
Marek, Houston

>From: Katharine Thayer <kthayer@pacifier.com>
>Reply-To: alt-photo-process-l@usask.ca
>To: alt-photo-process-l@usask.ca
>Subject: Re: Gum hardening: top down experiment
>Date: Wed, 12 Apr 2006 17:05:21 -0700
>
>I don't know if anyone was planning to try this with Pictorico, but just
>in case, let me report that I just used my last piece of Pictorico for a
>quick experiment and I wouldn't recommend it, for several reasons:
>
>(1) Pictorico goes sticky when it gets wet, so it's very difficult to
>smooth out the coating; the sticky coating on the Pictorico hangs onto
>the gum the way it was laid down with the first stroke of the brush, and
>that's how it stays. You just can't move the gum around on the surface.
>
>(2) the coating on the Pictorico hangs onto the dichromate, as some
>paper/sizing combinations do, and the Pictorico will take on a bright
>yellow cast that will have to be removed with metabisulfite.
>
>(3) you can't dry it with a hair dryer. This may not be a problem for
>those who don't usually use a hair dryer, but that's how I always dry my
>gum layer, and the heat turns the Pictorico white. This cleared to clear
>after a while, on the first drying, but on the second drying (after
>treating with metabisulfite and rinsing in water again) I found that the
>white didn't go away in some places.
>
>Other than those few things, it really makes a great image.
>Katharine
Received on Thu Apr 13 08:06:31 2006