Step 1: Prep Your Piece
Next, you're going to want to cover all of the copper that you don't want eaten away. I got away easy with my piece only needing to be partially submerged.
Step 2: Prepare Solution!
This is basically just warm water and salt.
Actually, it IS just warm water and salt.
Step 3: Some Assembly Required
It is imperative that these do not physically touch.
After these have been prepped, go ahead and hook them up to your power source. I used a 6v Lantern battery, but this is something you can choose yourself as different power sources will result in different quality etches.
Step 4: Waiting
Go ahead and do something to pass the time.
Step 5: Cookies Are Done!
Beware that if you're not careful, you can make a royal mess.
Rinse your piece under water to remove and residual gunk and then peel away your resistive material.
You should now have the design etched into your copper.
The depth may vary depending on distance between electrodes, Wattage, salt content of the solution and the amount of time you waited, but so long as you didn't rush the process it should be acceptable.
Go ahead and sand it with emery cloth or steel wool to bring out the shine.