Basically, all you need to do is hook up a D battery to two pieces of copper suspended in a saltwater bath. One is the piece you are etching, the other can be any piece of scrap copper. The current draws copper from the etching piece to the scrap copper. You can use the same kinds of resists you would use for acid etching, but you don't need the etching chemicals. Neat huh?
Here's what you need:
- D battery
- D battery holder
- Alligator clips
- Heavy copper wire (14g. is good)
- Copper to be etched
- Scrap copper
- Pure salt (kosher or canning and pickling salt)
- Plastic or glass container
- Resist (pnp film, stop-out varnish, asphaltum, etc)
To get your metal ready, you need to get the piece you will be etching really nice and clean by scouring it with a scrub pad or heating and pickling it, then draw your design on with whatever resist you are using. I was surprised when I first started experimenting with this technique to find that the salt water is just as hard on the resist as the ferric chloride was. Permanent marker didn't work at all, and the sharpie paint pen I used to use for beads works ok but doesn't last long enough to get a good deep etch, so I am back to using the stop-out varnish (check out my acid etching tutorial for more info on different resists) The scrap copper just needs to be cleaned off with a scrub pad or brass brush to remove any residue, then it's ready to go.
Once your metals are ready, fill a plastic or glass container with the salt solution, then attach your two pieces of copper to copper wires and hang them from the sides of the container so they are submerged in the solution. Attach the positive alligator clip to the piece you want to etch and the negative clip to the scrap copper. You will immediately see little bubbles rising from the scrap copper, and within minutes the water will start to get cloudy and reddish brown with copper (Note: Don't pour this water down the drain! collect it and talk to your local waste management people about how to dispose of it. It's not hazardous to handle but it's not good to put copper into the water supply!)