Etching Copper or Brass the Cheap & Easy Way (Updated)

I usually think of metal etching in terms of making printed circuit boards, but this basic technique will work whether you want to push electrons down a chute or just want to etch “TOIL IS STUPID” on a copper bracelet. It’s all rock and roll.

I’ve been doing PCB etching since I was 15 or so. For most of those early years I manually applied the resist mask, either using a Sharpie-like “etch resist pen” from Radio Shack, or a grease pencil, or layout tape, or rub-on decals. Later, the more ‘sophisticated’ photo-etch process was used (note: don’t bother using the spray on emulsion, it has never once worked for me: stick to pre-sensitized boards or look into the photo emulsion films out there) but for quick& dirty prototypes of two layers or less I’ve migrated back to using the “toner transfer” method: laser printing (or photocopying) a design onto the cheapest photo-paper available, then ironing it onto copper clad boards (or brass/copper sheets) with a clothes iron.

It works really well & is cheap and easy (just like me)….

Here’s the method that works for me (photos coming next time I etch something)- but nota bene: this version of the “toner transfer method” is most suitable for fairly shallow etches (20 mils or so) on flat substrates. Of course, it can be augmented with manually applied resists after initial etching if the toner resist gets undercut or starts to ‘let go'(hey, it happens): asphaltum, shellac, lacquer, waxes & etc can all be applied on an as needed basis.

1. Create your artwork. For PCBs I use EagleCAD. There’s a (limited) free version available at www.cadsoft.de , but use any drawing program you have handy. I’ve made a tweaked parts library to make one-off circuits, with all the pads set to as large a diameter as possible, with the through-holes shrunk to 10 mils: this helps center the drill when “punching” the boards I make myself. For other free-form artwork, just remember that lines finer than 10 mils are going to be tough to transfer and etch reliably.
2. Print your artwork out mirrored (‘horizontal flip’ or whatever your software calls it, so any text or footprints won’t be backwards) onto cheap glossy photo paper. I’ve had great luck with “Office Depot Multi-Project Photo Paper” which is their low end paper, but it works better than the pricier ones. If you can give the photo-paper a tounge-test, you want the glossy side to feel starchy when wet. If your laser printer supports it try setting it to print on “Transparency” to put out as much toner as possible.
3. Plug in your iron and crank it up to the highest setting. My iron is just for ironing metal, so it has never seen any water, but if yours has you best be emptying it out beforehand and allow extra time for all the water to cook off as steam will definitely screw up the transfer process. Give even a dry iron a full 10 minutes to get up to temperature, you’ll be glad you did. While the iron heats up you can—
4. Get your metal very clean and grease free. Start with hot water, scotch-brite and some abrasive cleansing powder, and scrub it like a maniac. Any shellac or varnish left, even oils from your fingers, will screw it up. After scrubbing and rinsing and wiping dry, get some acetone (beauty supply or paint store) on a paper towel and give the metal a good firm wipe-down. Check for residue on your paper towel; if you see grunge there, keep wiping it down with fresh acetone and new paper towels until you get nothing off it. That’s clean enough. Use a blow drier to get it dry now if you feel strongly about it, or just let it dry at its own pace.
5. You’ll need a hard surface to iron on. I have a chunk of half-inch aluminum plate now, but some thick cardboard or a dry wooden cutting board will work just fine. Place your copper-clad board or sheet of metal on the hard surface and position your laser-printed artwork face down on it. Take the hot iron and press the artwork onto the metal. You’ll want to press fairly hard, but not hard enough to smear the toner image. I’m guesstimating 10-20 pounds of pressure while moving the iron around a bit. By the time you can see the artwork through the photo-paper you’re probably pretty close to done: the metal is hot and the toner is melted to it.
   If you are doing a two sided design or PCB, place a couple of fiducial marks (I use tiny pads with tiny holes) on opposite corners outside the main body of the design. Drill the fiducial holes with a very fine bit, then use pins to align your second-side artwork.
6. Safely put aside the iron. Take the metal with the photo-paper now firmly adhered to it and drop it into some water. I use the bathroom sink. You want the whole thing submerged and the water to saturate the paper, so leave it there for at least 10 minutes and don’t rush it. Once the water soaks in, the “starchy” emulsion side of the photo-paper will release the toner which is stuck to the metal. As a rule, if I try lifting the paper and it picks up the metal without letting go it isn’t ready yet!
   Don’t rush it, let the water do its job: this has never taken more than 30 minutes for me.
7. Once the photo-paper has turned loose remain aware that touching the metal will leave oils that can muck stuff up. Don’t sweat it if little bits of photo-paper are still stuck to the metal. The etchant doesn’t care about the paper and will go through it. You want as much paper off as possible, with as much artwork stuck to the metal as possible.
8. You should probably wear gloves and goggles and personal protective equipment for this and all following steps. Mix two parts of muriatic acid (AKA dilute hydrochloric acid from the hardware store) to one part hydrogen peroxide (from the drug store). This mixture is your etchant, which will work for copper, brass, mild steel (somewhat) but NOT aluminum (which will dissolve rapidly and make a stink). I really can’t stress enough how much nicer this concoction is than the Foul Brown stuff is when it comes to NOT staining the sink or your fingers. While still a “nasty chemical” is is far more benign than many (N-stoff, for example), but you should wear your personal protective gear anyway (could blind you from eye contact, or soften your hands). It is very transparent, making it much easier to monitor the status of your work as it etches. (Some people will add one part water: try it yourself. Me? Instant gratification takes too long).
9. Pour the etchant into a glass or plastic container big enough for your artwork-enhanced piece of metal. You want enough to cover the metal, and all the uncovered metal will be etched. (I’ve found that vinyl “contact paper” makes an excellent masking for the reverse side of metal sheets and circuit boards).
10. Plunk the metal into the etchant, watch and wait. You will notice the etchant turning blue-greener as the process goes on (almost immediately from the start, aye). This is the copper chloride building up in the etchant, which will gradually become spent. If you see any breakdown in the masking or artwork you can pull the metal out of the etchant, rinse it off well and apply touch-ups with a Sharpie pen, black tape, nail polish, wax, asphaltum, whatever will block etchant, then plunk the metal back in (this is not rocket science).
11. When it gets etched enough for your tastes, take out the metal and rinse it off. You can remove the toner with acetone (from the beauty supply house) or just good old scotch-brite/abrasive cleanser/etc.

NOTE: You might want to save your spent etchant for a kinda neat trick (H/T to MAKE Magazine).
A clean tin can (real tin plated steel, that is) placed in the spent etchant will have copper deposited on it in a manner much smoother than what you get out of copper sulphate on ferrous metal.
I haven’t got around to trying to do an electroplate with this spent etchant yet, but I’ve read encouraging hints… and have several quarts to play with. Stay tuned.

Update: If you are going for capital A ‘Art’, and not PCBs or some-such, you’ve got a broader range of options:

1. Use tape or contact paper (with a hole cut in it where your art will go) to mask off the bulk of the copper or brass piece you want to etch.  (All metal cleaning steps above still apply, prior to masking!).
2. Fill in the hole in the mask with a good smear of silicone grease (from the home improvement store plumbing aisle) or beeswax, or shortening or lithium grease, etc.
3. Apply your caligraphy to the grease with a toothpick (or tool of your choice) to expose the metal to the etchant.
4. Etch the metal as described for PCBs, above.

The best thing about the peroxide-HCL etchant is that’s it’s relatively benign to skin, allowing you to amend your designs as you go, and it’s fairly transparent so you can monitor the goings on in progress. More like cooking than baking that way, eh?

You might also want to check out the more recent entry Parchment PCB Toner Transfer: Updated for a newer twist on toner-transfer etching.

Tags: brass, copper, etching, fun science