Gum transfer

There were a lot of interesting posts this weekend and I am going thorugh
them now. I have done a few more gum transfer experiments. Here are some
observations and issues.

When exposing a gum layer through the substrate (glass, polyester, etc).
This is "expose through the bottom mode" heavy pigment concentration is OK,
coating imperfections are not that critical as the air bulles rise to the
top, streaks in coating are also on the top. A thin image layer that adheres
well to the substrate after development shows relatively few imperfections
and looks suprizingly good. I have not done much more on that as I am
waiting for a sunny weekend where I can experiment with some gum on glass.

Gum Transfer.
Here is how I approached it. I though it would be very difficult to transfer
actual developed and hardened gum image by means of softening it and
transferring to the paper. Instead a process similar to a single carbon
transfer was appealing to me. Here is what happened.

I coated a few sheets of plyester with same emulsion (gum, lamp black,
ammonium dichromate) that I used in my previous experiments (expose through
the back). This time I exposed in a traditional way from the top. I will
call it the gum tissue. This should form a hardened image on top of the gum
layer with unexposed and soluble gum on the bottom. We know what happens
when you put this image in water. Everything just slides off.
OK, I then placed the gum tissue on top of gelatine sized paper, made a
sanwich let it sit for a while and placed in warm water to start dissoliving
unexposed gum so that the tissue and the support could be separated. Then
just wait until the water dissolves the rest of the unexposed gum revealing
the image.

Some of the difficulties. Even a very short water immersion (cold or warm)
of the exposed tissue to remove dichromate softens and starts dissolving the
gum, no usable image can be transferred.

The tissue image needs to have decent mechanical strength for the transfer.
It needs to be thicker, which suggest less pigment, thicker coating.

All the air bubbles and imperfection are on top, where the image is formed.
There are all visible in the final image. Rollesrs and other means of
smooting out the coat do not work with thick layers.

My impression is that because the dichromate is present in the transfer
process for about 30 minuts, before tissue is pulled away, I am getting a
dark reaction, or something, as I am not getting very clean highlights. My
exposure might be too long, or dichromate concentration too high as well.

My negatives are for Pd printing, not for carbon. Just a minor issue.

As Sandy noted I could print in carbon, but it is such a finicky process
that requires a very precise time and temparature control.. I am still
hoping that an easy way of transfer could be found with gum, or perhaps
gelatine/gum mix as I am thinking now.

I have one picture from this trials and perhaps Katharine would be so kind
to add it to her site.

Marek, Houston
Received on Mon Apr 17 11:44:36 2006