Etching Copper and Brass for Sundials

Photo-etching of brass (and nickel-silver) is widely used to produce solder-assembly model construction kits in the UK in a number of areas, with railway modelling being one of most prominent. The technique involves producing a matching set of transparent drawings full-size for the part(s) to be etched, coating the brass sheet with a photo-resist material, and exposing the brass through the drawings so as to destroy the photo-resist by light exposure. The exposed brass is then immersed in an etching fluid that attacks and dissolves the brass where the photo-resist has been exposed, leaving a 'fret' of brass showing the required parts' shapes. Using a pair of drawings in register means that the brass can be fully etched through in some places and half-etched in others, giving some valuable 'depth' to some parts as may be found useful in model-making. Once one brass plate has been exposed it is then a matter of repetition to produce any number of brass 'frets' from a pair of master transparencies. The transparency technique enables transferring the desired product into other scale ratios to take place easily, with a major avoidance of new product development costs.

There is a significant 'cottage industry' in the UK turning out this sort of material, enabling the home hobbyist to turn out some most agreeable miniatures.

For a single-sided object like a clock face it is likely that only a single transparency may be required.

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If you want to mass produce these items the answer is to make silk screens and then print the etch resist ink onto the brass or copper. This is how the electronics trade make circuit boards. Ferric chloride then etches the pattern be careful it stains very easily and is all but impossible to remove. It is also highly corrosive. Wear good rubber gloves when handling things.

Check out 'Toner Transfer System' at www.dynaart.com.

I've used it for years to make circuit boards, both single and double-sided. It's hardly perfect, but I think it would do what you want very nicely. You simply create your art on your computer, flip it end-for-end (so it comes out in the correct position for upside-down attachment), and print it on a monochrome laser printer using their special paper. You then iron this paper onto the surface to be etched, and soak it in water until the paper floats off. Wherever toner remains, it protects the copper etc. from the etchant (normally Ferric Chloride).

It does take some practice to find the correct heat and pressure, and I nearly always have to touch it up (with diluted fingernail polish), but its quite a bit faster than making a silkscreen for onezy-twozys.

Ferric chloride, ammonium persulfate, hydrogen peroxide (50%) All these will etch copper but are pretty nasty and the HO will spontaneously ignite most anything flammable. The ammonium sulfate is a crystalline powder you mix with water so may be safer to store and ship. I suggest you find someone who offers a system that also provides a means of disposing the nasty remains.

It seems that etching is a pretty nasty, toxic, bio-unfriendly process (sort of contrary to the whole zen of sundials). Have you looked into casting, stamping or tooling?

Oh hell, keep it simple.


Use a simple wax resist, (you can acquire this at any pottery supply house).

This you can use free hand, or with a stencil that you make from 4 mil film.

You can also suspend the wax (water emulsion) and use an air brush. Stencils work great for this. Also you can use tape and cut the pattern, spray wax resist, dry, then use a standard copper etch, there are many etch systems dependent upon the surface you wish at the end.

SC