Since the process is very like photography the best analogy is to consider what one does to get a photographic print. First you take a picture of something, then you develop the film to make a negative and finally you expose the negative on to a suitable paper and develop it to make a print.

Photo etching is a very similar process, with the "negative" being a graphic template output from a vector based illustration program, which is exposed onto a sheet of specially coated metal. The final developing process is a little different from photography since instead of getting a picture you get a sheet of metal with material missing from both sides.

The actual material used to coat the metal before exposure is somewhat special. It is a photosensitive laquer which, when exposed to ultra violet light and developed in sodium hydroxide, hardens and becomes impervious to the etchant used in the etching tank.

After exposure of the image onto the sheet of metal it is put into a developing tank where the etchant (usually boiling ferric chloride) is applied until the outlines of the parts appear. At the end of the etch the metal sheet is rinsed and the protective laquer removed chemically.

How can I polish my photo-etch to a chrome-like finish?

1. Please remember to always wear safety glasses when working with photo-etched parts.
2. Remove any parts that you do not wish to polish. Store them in either a resealable container or on a piece of scotch tape so that they don't get lost.
3. Lay the remaining photo-etched parts that are still attached to the frame onto a pane of glass. A mirror could be used for this purpose as well.
4. Apply a small amount of metal polish off to one side of the glass. I like to use Wenol brand because it's easy to clean off the photo-etch. You can use other brands, but it all depends on what works best for you.
5. Use a rotary tool like a Dremel or Raobi with a #401 mandrel and a #414 Dremel polishing wheel. Set your rotary tool on its lowest setting, or about 1,000 R.P.M. Gently ease the polishing wheel into the small amount of polish that you previously applied to the glass. Hold the photo-etched frame with your fingers and begin to gently polish the metal from left to right. The weight of the rotary tool is all the pressure that you need to apply. DO NOT ALLOW YOUR POLISHING WHEEL TO PASS OVER THE RIGHT EDGE OF THE PHOTO-ETCH. The rotation of the polishing wheel will lift the right edge of the photo-etch and bend it or damage it beyond repair. Polish up to the right edge and then turn it 180 degrees so that the right edge is now on your left. You can now work on the unpolished portion. Continue to polish until a bright chrome-like shine is obtained. Don't forget to polish the backside of the rear view mirror.
6. Although your photo-etch will have a great shine, it will also have a lot of black residue on it. This is caused by a combination of oxidation and used polish on the surface of the metal, but is easily removed. Lay the photo-etch in a flat container. Using a cleaner like Simple Green, 409, or Fantastic, spray the photo-etch so that it can soak in the soap for a few minutes. Use a soft bristle toothbrush to gently clean the photo-etch. Be careful around parts that have small openings like grills as toothbrush bristles can easily get snagged in them. After you have loosened the residue, rinse in warm water.
7. Let air dry or tamp dry with a cotton cloth like an old T-shirt.