I have been trying to etch metal with varying results over the years. I live in Alaska and it is very expensive to get the "real" stuff here because of shipping. I first read about copper etching here http://www.makersgallery.com/goss/etch.html but had a hard time at resists. Please read her page for the etching process, I have added a quote here, but she tells it so much better than I.
"This method of etching uses a prepared ferric chloride solution which also contains hydrochloric acid. This "etchant" is not a pure acid, but etches copper and copper alloys (like brass and bronze). It will not work on silver. It is available from electronics supply shops, such as Radio Shack or from chemical suppliers. It is generally used to clean or etch copper circuit boards. It can also be found at some printmakers' supply stores.
Advantages over Acid etching:
not a pure acid; does not require dilution; is not as dangerous or tricky to use
resists are readily available and easy to use:
permanent markers that are made for writing on plastic can be used as a resist, which allows for drawing and writing directly on the metal. Photocopies, liquid floor wax and packing tape can also be used as resist:
fast working, clean bite "
I found that using a pen did not hold up well and showed all of the lines as the pen passed over itself. I also have terrible handwriting and don't like my drawing skills much. So, about a month ago I have been diddling with trying to make my earcards nicer and all this stuff, I went to the stamp store and bought some stamps and etching powder. They did not help my earcard in any way, but my mind was thinking... So, after trial and error I have found a way to stamp and etch copper.
First, the copper must be sanded with a fine/medium grit paper. I actually use nail files from the beauty supply, regular sand paper was a pain. Making sanding sticks was worse. The whole surface should be sanded clean and have a matte finish. If it isn't, the liquid moves and the results are spotty. Use the etching pad, stamp, apply powder, shake off and clean up the design. Now is the tricky part, use the heat gun, it takes longer because the metal is a conductor and is cold, needs to heat up, then stays hot for a while. I overheat it to get the powder to flow. Make sure you have your piece on a heat resistant surface. I use a 6" anvil. It is metal, but is too big to get hot and cools my piece off faster because I am impatient.
I use nail polish to cover the back and any areas I don't want etched. I tried to paint with polish as the resist, which would work, but I did not get the results (mostly because of the ugly design). You could also use contact paper, packing tape and make a stencil, but I am impatient.
Pop the creation in the ferric chloride, and wait... I usually check it after about 15 minutes, which isn't long enough. I use a toothpick to see if it is etching, a hemostat for tweezers. The acid gets black and it is hard to see what is going on so rinse and check, then chuck it back in the solution. It can stain clothes and your skin so be careful when chucking. I should wear gloves, you should wear gloves.
When it is done, I brass brush it, pick off the etching (with the side of a dull pocketknife) use nail polish remover on the back and there it is! I soldered it to this bracelet and used a rivet, mostly for decorative purposes. Oh, I hammered the edges as well. I used 20g for the copper and etched it for a while so it was deep as I was making a cuff that would have to withstand some wear and tear. I don't much like the thinner metal I've used, not as dramatic. Anyway, here is the finished product. Easy peasey!