etching negatives onto Bronze or other metals?

[Daniel_Buck]

So, while on vacation I saw an episode of Mythbusters on TV that had something to do with transfering negatives onto sheets of bronze, I believe they were etching fingerprints onto the bronze with some chemicals and UV light or something like that.

But anyway, that got me thinking, what would be involved in printing to sheets of bronze (or other metals) instead of regular printing paper? I'm guessing the use of some chemical that causes a reaction on the metal when UV light is shown onto it? If a photographic negative were projected onto the bronze that has the chemicals that react to the bronze with UV light shown on it, a positive image would be etched into the metal, correct?

Anyone ever done anything like this, or know of any resources for doing this? It's got my interest, and I'd like to give it a shot if it's not terribly complicated or posing much of a chemical hazard

[panchro-press]

Check 'photomechanical reproduction'. Photoengraving, photolithography and gravure all do what you're mentioning.
From what I recall ( I used to work for a newspaper ) all of them required an acid etching bath which could answer your question about safety.

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[Marko]

On the other hand, electronic printed circuit boards are made using ferric chloride, which, while also highly corrosive and moderately toxic, is nowhere near as dangerous as any of the acids traditionally used for etching. PCBs are based on copper, but ferric chloride should also work well on bronze.

There are also electrolytical etching methods, which are fairly "green" compared to traditional ones. Google it around and you will find a lot of starting information.

[Daniel_Buck]

Thanks for the replies yall, I will look into them. Especially the "less lethal" methods, haha!

[Marko]

And don't forget to post the results here!

[domaz]

You can etch with a mixture of Muriatic acid (Hcl?) and Hydrogen Peroxide. Supposedly this solution can even be re-used. In my experience it only works once though. Google and you should find instructions for this.

[panchro-press]

Gee, as a Ham, KD8VI, I should know about etching circuit boards. Must have been late.

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[Laura_Campbell]

I print my photographs on an etching press using the KM Printight plates by Toyobo. The plates used for photography are the KM43, and the KM73. They are processed in water rather than acids. This process is called polymer plate photogravure, or photo polymer gravure. If you want to end up with a print on paper (a positive) you shoot your negative, then make an interpositive, then print the interpositive on the plate, ink with etching ink, wipe, and run your plate and paper through an etching press. The plates run wholesale a little over $4 per plate for an 8x10. The best exposure unit for these type of plates is a plate burner which has a mercury vapor lamp or metal halide, and a vacuum frame.

[Nathan Potter]

Laura, are you saying the actual plate is made of polymer and the polymer is etched when exposed to water? The mask is a positive so produces a positive image? Sounds interesting. I take it you don't do bronze since bronze would not be etched by water.

As a point of interest I once did a few experimental images on aluminum. I forget the mask material but it was used to block anodization in a dilute H2SO4 solution so was a negative acting process. The negative was halftoned on Kodalith Ortho film and printed with UV mercury lines. The anodic film could be pigmented to a brilliant color depending on the dye material whereas the unanodized aluminum does not accept the dye. Anodic aluminum is actually porous with pore size depending on the anodic bath material and the rate of anodization so the pigment can be adsorbed by the pores. Versions are common industrial processes and since the films are porous the process can be used to build up quite thick films of the aluminum oxide, Al2O3.

A similar but even more spectacular process I had been working on was the selective anodization of images on niobium films and pieces. In this case the anodic film of niobium is clear so the thickness can be tailored as a function of bath time to show dramatic interference effects in the thickness ranges of say 80 to 300 nanometers. Using multiple halftone masks several interference colors can be obtained in one image. As the angle of image view changes, the color changes, providing a bizarre rainbow effect from the image. Single coats of oxide are common on chunks of niobium in the jewelry business but I've never seen it adapted to photo imaging art.

Nate Potter, Austin TX.

[Laura_Campbell]

Hi Nathan! The plate is steel with a light sensitive polymer coating. The coating becomes hardened and water insoluble in direct proportion to the amount of light it receives. Yes, it is the polymer that's etched, not the steel backing. No bronze for this girl!