Re: Gum transfer

Marek, you betcha I'll add your image to my site. I'm right now
trying to replicate your results with the thick heavily pigmented
coating, with some interesting, not 100% successful, results, but the
one that's soaking now looks promising. I've had a very difficult
time getting the very thick gum layer to stick through development on
untreated mylar, trying to replicate your conditions, and have had
to retreat to the scuffed mylar. I wonder if your transparencies are
made of some other more gum-accepting material.

Katharine

On Apr 17, 2006, at 10:44 AM, Marek Matusz wrote:

> 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 11:53:31 2006