What is photo etching? How is it done?
Photoetching is a process that involves removal of metal through the use of chemicals. The process
and materials are widely used in the electronics industry.
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?
Please remember to always wear safety glasses when working with photo-etched parts.
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.
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.
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.
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.
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.
Let air dry or tamp dry with a cotton cloth like an old T-shirt.