I have been working with big aluminum plates this summer and had promissed
to give a report to the list. This has been postponed due to health
problems, but here it is.
I started my experimenting according to the following approach:
All materials/processes are looked upon as:
Group 1. Chemical compositions, that react to UV-light and produce an image
in color without (or with) additional pigments by projection, contact
copying or photogram method (f.e. cyanotype, kalitype etc.) These
compositions are water-based and sink into the underlying surface. They can
be applied to paper, ceramics, wood - any surface, that soaks water. One
can use materials from group 3 to control absurbency of the surface or to
create an absorbent layer on non-absorbent surfaces such as glass, metal,
plastic, glazed ceramics etc.
Group 2. Light sensitive emultions, that have a base and create a layer of
certain thickness upon the underlying surface (like gum arabic, other
dichromated colloids, silkscreen emulsions etc.) These emulsions can be
used as a resist for coloring, etching, sandblasting or some pigments can
be mixed into a composition to produce a final image. They can be water or
oil based.
Group 3. Materials, that can be used as bases for light sensitive materials
and colors in group 2 and as impregnating components for group 1 (and 2).
(Like gum, gelatin, acrilic, lacquers, glue, asfalt, bitumen etc.)
This aproach applies as a matter of fact to all surfaces, that we use in
alternative photography, inkl. paper. Maybe, one can get new ideas, if one
starts looking at it this way:
How about creating white on white photographs in relief by sandblasting
thick paper or porcelain ?
How about cyanotypes on aluminum ? (Blue on blue pictures)
I worked with:
1. CYANOTYPE. I have tried it and liked the results. I have not impregnated
the surface, but polished it mechanically or chemically (alkaline etching
by NAOH). One can experiment with different proportions between the
emulsion components and by adding gum arabic solution to the emulsion to
give some "body" to the print. I imagine, that kallitype would work as
well, I have not tried that. The image can be protected by a layer of
transparent lacquer by the end.
2. AQUASOL EMULSION / SANDBLASTING. Waterbased silkscreen emulsion applies
directly to mechanically polished aluminum plate and is permitted to dry in
the dark. High contrast (or rastered) image is projected directly or
applied by contrast printing. It is developed by water, dryed and
sandblasted, the emulsion is removed by hot water and/or emulsion remover.
The image results as daguerrotype, in two types of shiny surfaces, one has
to find an angle to see the image. I liked that most of all ! Endless
amount of variation according to surface treatments and negative quality,
positive/negative variations, nearly no size limits (if you have no cabinet
sand blasting possibilities).
3. PHOTORESIST / ETCHING. That works, as it is a well-known method on all
kinds of metals (zink, copper, steel, silver). I experimented a bit with
selvcomposed resists, based on glues, gums, gelatins, lacquers, asfalt etc.
This was very difficult, as either the resist does not stick to the plate
(even if one prepares it mecanically) or it falls off in the etching bath.
The only thing that worked for me was a standard photoresist in a spray
box, that I ordered from Germany. That was fun to work with, but it is
expensive, which gives size limits. So I abandoned that pretty soon. I
believe though, that it should be possible to find a resist, that is cheap,
homemade, sticks well to aluminum and is resistant to etching. There are
several types of etching baths one can use on aluminum:
- degreasing (alkaline or acid) - NAOH or sulphuric acid (H2SO4)
- etching/polishing - Königs wasser (Aqua Regia) - 320ml Hcl + 160 ml HNO3
- Keller solution (1,5% HCL + 2,5% HNO3 + 96% water)
We used also something called dandruff acid (HF) for micro etching/polishing
(can anyone tell me what it is called in english ?)
4. ETCHING/ANODISING/COLORING. First, the plate is prepared by mechanical
and chemical cleaning, so it is etched to give the toof and polish before
the electrolyting. The emulsion has to be applied after the anodising
(electrolyting) and before the coloring bath. One has to be very quick and
careful, so as the anodised surface does not get hurt. That is not easy and
the only thing that worked for me was that standard resist spray box from
Germany. Again, it is only a matter of time to find a selfcomposed emulsion
and how to apply it without disturbing the anodised layer. For color bath
one can use organic anilin textile colors or just anything else. The colors
are usually bright and strong, very punky and beautiful. One can repeat the
process several times to get color separations, I imagine. I have not done
it as I had time limits. The problem would be to protect the first color
from being etched away, but there must be a way !
My approach should be correct for any other metal. One has to find the
right chemicals though. There were questions on the list about silver -
here you go !
I worked at a big plant with crazy security routines and I worked in a
really big scale. That in itself has its limits. Anodising is usually used
for jewelery, here they produce plates 1 x 7 m for architectural use. I
will try to go back to that next year.
Regards,
Galina.
Galina Manikova. (galina@online.no)