Well, I do not know but I'd bet that LaPlantz does. He was very friendly when
I talked with him on the phone. I am sure that he will not mind if you call
him at home. (707) 822-6009. For one thing he publishes his home phone
number in his book and he seemed very interested in talking about his
projects. So my suggestion is to give it a try.
The anodizing process results in a surface that looks like a bunch of tubes
sticking straight out of the surface. The dyes get in the tubes and then the
ends are sealed by thermo-chemical means. The simplest one being to boil the
aluminum in plain water after dyeing it. So you need a process that gives
you tube length or tube diameter proportional to exposure. If there is a
chromated colloid or other photo layer that will stand up to hot dilute
sulphuric acid and will allow current to flow proportional to thickness then
I'd say there is a good chance. You could get differential tube lengths or
diameters. Either one or some combination would allow for a grey scale.
The anodized surface is aluminum oxide which is at least semi-transparent.
Maybe you can dye the surface with a photreactive material, expose, wash out
or somehow inactivate the unreacted material and then seal. There would
be a development step in there somewhere. The problem here is the small size
of the tubes which may physically block some things from getting in the tubes.
One of the other common anodizing processes uses chromic acid instead of
sulphuric acid but the resulting layers are much thinner. They are also
harder which is a good thing for metallurgy but may not be for photography.
Chromic acid may be more compatible with chromated colloids. Phosphoric and
boric acid have been used but there are limitations with these.
If the layer will stand the acid then I can see a carbon black image giving
the proportional current flow. The first experiment may be to do a transfer
and then tan the layer like crazy. Lots of variables but it might work.
The anodizing process is significantly blocked by traces of grease on the
surface. Standard lithography on aluminum printing plates generates a surface
with a kind of proportional greasiness which picks up the printing ink
proportionally and makes the image. Depending on the nature of the
sensitivity of anodizing to grease this might do it.
Last of all there is the good old half-tone screen process to deposit
variable sized dots of some kind of material so that you wind up anodizing
the dots or everything else but the dots. I'd bet that can be done relatively
easily but I don't think that is what you had in mind.
If LaPlantz is no help let me know and I'll dig deeper. I can go through
the Thomas Catalog and call some of the big time anodizers. If it can be
done they will know and they are very likely to tell how. If there is a
commercial anodizer you can reach give them a call.
Let me know how this turns out or if I can help further. I am always
interested in something new like this.
Gene Robkin