How to Electro-Etch a Solid Metal Plaque





Introduction: How to Electro-Etch a Solid Metal Plaque

About: I'm the Founder and Chairman of TechShop.

This is a technique that has been used by humans for a very long time.

Learn how to create a deep electro-etched metal plaque with household items or items from the hardware store in this Instructable.  There are no hazardous chemicals (except dihydrogen monoxide and salts of sodium and chlorine), no dangerous voltages, and no toxic chemicals to dispose of.  Be aware that the metal that disappears from your etched metal does end up in the water, so you will need to pay attention to any local laws about disposal of metal particulates.

This is a great technique that makes it really easy to go from virtual artwork of any type to a dimensional 3D surface.  From there you can use it ti burnish and emboss paper, create molded items, make stamps, steam punk data plates, or anything else where you need to have 3D art from your 2D computer graphics artwork.

In this sample project, I will be creating the plaque from a 1/8" rectangle of brass as shown in the second photo.

So read on if this is something you would like to be able to do yourself.

Step 1: Here's What You'll Need

You will need the following items and supplies:
  • Piece of brass, bronze, aluminum, steel or stainless steel, or any other metal
  • Vector graphics program or other program to create the art for the CNC vinyl cutter
  • CNC vinyl cutter
  • Self-adhesive vinyl sheet for the vinyl cutter, any color is fine
  • Tub large enough to hold your piece of metal
  • Salt
  • Water
  • Battery charger or charged car battery (or other similar DC power supply of 5 to 10 amps or more)
  • Wires to connect the power supply to the piece of metal
  • Sacrificial piece of metal (preferably stainless steel, but any metal will work)
  • Electrical tape

Step 2: Create the Artwork

Use your favorite vector graphics program to create the artwork.  I used Adobe Illustrator, but you could use any vector-based design software including Autodesk Inventor, Autodesk 123D, Inkscape, or others.  Any shapes you create will result in the raised areas on your finished plaque, and the areas where there is no artwork are the areas that will be etched away.  Try not to make the details too small because the vinyl cutter doesn't really do a great job with tiny cuts.

You might need to perform an operation to convert any live text into vector outlines.  The resulting artwork from this process is shown in the second photo.

The artwork shown is from my first pass through this project.  Because the very tiny type of the tagline under the TechShop loco ("BUILD YOUR DREAMS HERE") and the "TM" by the letter "p" in the TechShop loco were peeling off on their own,  I took those out of the artwork.

Step 3: Cut the Mask With the Vinyl Cutter

Use the CNC vinyl cutter to create the vinyl mask.  The exact procedure will depend on your particular vinyl cutter.  After you have cut the vinyl, "weed" out the unwanted areas from the cut leaving only the parts of the artwork which will represent the un-etched areas or high areas on your plaque.  After the unwanted areas are weeded away, place the backing sheet over the face of the vinyl mask and peel off the original vinyl backing sheet.

This vinyl cutter is at TechShop San Francisco, but all TechShop locations have a CNC vinyl cutter.

Step 4: Apply the Vinyl Mask to the Metal

Clean the metal completely and make sure it is dry.  Apply the vinyl mask to the metal, burnish down all the pieces and peel off the backing sheet.

Instead of "weeding" the unwanted vinyl before you place it onto the target surface, you can also just apply the entire cut vinyl with the backing sheet, and then weed it after it is on the target surface.  In this case, I found that to be much easier.

Step 5: Prepare the Metal for Etching

Connect a piece of wire to the back of the metal.  You can do this with solder, an alligator clip, or by taping the stripped and splayed wire to the back of the workpiece with electrical tape (as I am doing here), or any other method you can think of.  After the wire is securely attached, wrap the back of the metal with electrical tape or an extra piece of vinyl sheet.  Cover all areas on the back and sides that you do not want to be etched.  Any metal that is exposed will be etched.

Step 6: Prepare the Sacrificial Metal Piece

Connect another wire to the piece of sacrificial metal you have selected.  In this photo, I am using some scrap galvanized steel for the sacrificial metal, but stainless steel is the best because it doesn't degrade and keeps the salt water cleaner.  You do not need to mask off anything on this piece of metal as it will not be etched.

Instead of a sacrificial piece of metal, you could use a stainless steel pot and put the negative (-) alligator clip right on the rim of the pot.  You would then put the workpiece into the pot, along with the salt water, and etch right in the pot.  You just need to make sure that the workpiece does not contact the pot electrically.

Step 7: Prepare the Etching Tank and Salt Water

Measure out enough water to cover your pieces of metal by about an inch or two, and mix a lot of salt into the water.  The more salt, the better it will conduct electricity and the better it will etch your metal.

Step 8: Prepare to Electro-Etch

Place your pieces of metal in the tub of salt water.  Connect wire from the piece of metal you want to etch to the positive (+) terminal of the power supply, and connect the wire from the sacrificial piece of metal to the negative terminal (-) on your power supply.  Then place the pieces of metal in the tub of salt water and place them as far apart as possible.  Make sure the side of the plaque that you want to etch is facing up.

Step 9: Electro-Etch Your Plaque

Turn on the power supply, and you should see bubbles start to come off the surface of your plaque.  Leave it to bubble for as long as you want.  The longer you leave it bubbling, the deeper it will etch.  If the salt water becomes really dark after a while, you can turn off the power supply and replace the water with new salt water and continue.  Be careful if you let it etch too long because you will start to get "undercutting" where the metal starts to get eaten out from under the vinyl mask.

In the photo, you will see a divider separating the tank's right and left halves.  The divider is only a chopstick and is only at the surface of the salt water, and serves to keep the red scum on the left side of the tub so I can see the plaque as it etches.

Step 10: Behold Your Creation

When you are happy with the depth of the etching, turn off the power supply and remove the plaque from the tub.  Rinse it off, and remove the vinyl and tape.  Remove the wire.  Your plaque is complete!

After I etched this plaque, I took it over to the sandblasting cabinet and sandblasted the whole surface, then I used an orbital sander to smooth the surface of the raised features to get the look that you see.

After I was done, I noticed that the copper/zinc chemicals in the salt water had stained my finger nails a beautiful shade of turquoise.  This was an undesired effect.  i suggest that you wear rubber gloves when you reach into the tank to grab your workpiece!

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186 Discussions


1 year ago

I just tried this with sheet steel. It worked great! However I am wondering what I should do with the solution now. I used salt water and in the course of etching it turned green brown. I'm assuming this isn't safe to put down the drain or in the yard but have no clue what to do with it. Any input would be greatly appreciated!

3 replies

If all you used is steel, than the green color is most likely Fe(II) salts, which are relatively non-toxic. If you left the solution sitting for some time it will probably become all brown as Fe(II) will oxidize easily. The nice thing about iron is, as far as transition metals go, it is very safe.

Hi KentR2...

Wow, that is a deep and loaded question!

I'll just say that there are a LOT of people on here with strong opinions about what is dangerous and what is not, and what will utterly and completely destroy the earth if it is disposed of in certain ways. You can look at the earlier comments to see what I mean. I will let those folks reply since they are the experts (actually, they're not, but they do have opinions...which as they say, we all have opinions and something else.)

I'm going to stay out of that argument because I don't know all the legal and physics issues involved, and I don't pretend to know, and I am not required to know before I'm allowed to write an Instructable, and that wasn't what I was trying to share with my Instructable.

From my research, you can pour just about anything on paper towels or newspaper and let it dry completely, then discard it with other dry waste. I've never understood why it matters if there is water in the substance when you throw it in the garbage, but that's what people keep stating, so OK.

Getting back to basics, I'm really glad that your etch worked! Awesome! Can you post some pictures?

Cat litter too!
I do this for brake fluid. Put the pile of the stuff in a bin, throw it next to the shop's exhaust vent, let it stay there until it's dry. Toss it in the trash.
Never done it with so *much* fluid before, tho, so this'll be fun.

Jim, I'd guess it'd be because our sanitation workers and environmentalists don't want all that stuff being dumped onto the roads when the garbage truck crushes the container ya put the fluid in. That's just gonna let it run down and out of the truck, and into the sewers. So basically just pouring it down the drain in another way.
That, and I'm sure the garbage guys don't want liquids sloshing all over the place more than they already do. :)

You should not use stainless steel as a sacrificial electrode, the stainless property is due to the presence of chromium atoms into the alloy. The chromium atoms will become oxidized and enter solution... you do not need to take my word for the toxicity of chromium salts, not only are they extremely toxic, such as chromium(VI) or hexavalent chromium, the disposal of chromium salts is also very highly regulated by the EPA and tested for during normal drinking water testing and as such, illegal disposal of chromium waste is also extremely illegal.

Very nice write up, A friend of mine is "apparently" using a similar technique to jazz up an exhaust on a bike, not sure how well it will turn out but will deffo post the results


1 year ago

So im attempting to etch some steel. I bought a new battery charger and its not working at all. Do new battery chargers have a safety switch that keeps ot from working?

1 reply

Short version: Maybe
It looks like TechShop was using a Schumacher SpeedCharger. Shumacher makes versions that are smart, like the kind it sounds like you have, and ones that are dumb, that just put out current. The latter is the one you need for this. They're less desirable when dealing with batteries, because they can overcharge and destroy the battery, but in this scenario, you don't want one with the 'smart' circuits that may only work safely--e.g. after it's verified it sees a real battery that it's designed to be charging.
However, you could use your new safe battery charger to charge up a large battery, and then use it to complete this project. It just needs to be able to put out high amperage...or lower amperage, and it'll go slower. Or so is my understanding.

Rapid bubbling means you are disassociating water. I use 5v from a pc power supply for my etching. I like to use an electrode that is as large or larger than my etch target. Things like proximity, solution concentration, total amperage all make a difference on etch speed. My setup is basically a copper grid electrode that sits 2 inches(5 cm) from the target face. I also use copper sulfate as my electrolyte, but I only process copper materials.

Also, for those in the US anytime you do electrochemical etching or plating your waste water is epa regulated.

Stainless steel is particularly bad as the electro-etching converts the chome to hexavalent chromium which is nasty nasty stuff and should never be put down a drain.

8 replies

Inhaled hexavalent chromium is recognized as a human carcinogen. Workers in many occupations are exposed to hexavalent chromium. Problematic exposure is known to occur among workers who handle chromate-containing products and those who grind and/ or weld stainless steel. Workers who are exposed to hexavalent chromium are at increased risk of developing lung cancer, asthma, or damage to the nasal epithelia and skin. Within the European Union, the use of hexavalent chromium in electronic equipment is largely prohibited by the Restriction of Hazardous Substances Directive.

Is hexavalent chromium created only if steel is the target of the etching, or does it also apply if it is used as the sacrifice piece? Is it a vapor, a sludge?

The chrome in question is only a product of electrically dissolving Stainless steels. Stainless is a combination of steel (iron and carbon) and chrome. So when etching away stainless the chrome dissolves into solution making it soluble and toxic. So not a gas, some in solution and some as sludge once the solution is saturated.

And only if etching stainless is it going to liberate chrome. The sacrifice piece gains metal from the etching piece so you would be plating the stainless which is fine.

Thanks! So, I do electro etching of bronze in Cupric Nitrate (hoping to switch to saltwater, but not sure it works on Bronze) and I am using a piece of Stainless Steel grate as the Cathode/Sacrifice... and that piece of Stainless is dissolving gradually!... it's not accumulating metal, as one would expect, it's getting covered in what looks like rust, and falling away around the edges. Any ideas why, and do you know if this might contain hexavalent chromium? Sorry to be such a pest, but there are so few people out there who have knowledge about this. Thanks again!

Well if the sacrifice screen is dissolving in the action its probably safest to assume the chrome is being liberated and this material should never go into the water table. When you are done with the liquid either dispose of it at a proper facility(preferred) or let it dry out to powder and store the solidus in a sealed container. This is safer than the liquid but should still make its way to a hazmat disposal facility.

What I would expect is happening is the tin and copper are depositing in a "sponge" structure which is delicate and will fall off. CuO is red and deposits in soft layers. If the screen itself is actually dissolving away slowly the chrome has to go somewhere. What % is hexa chrome(VI) or is still chrome(IV) I wouldn't be able to tell you, but I treat any electrochemical solution as hazardous just to be on the safe side (of the law).

Amazing info, thank you. (I'm unreasonably excited to have found someone who knows what they are talking about with this stuff.) :) I think you are correct about the tin and copper collecting in a soft layer, as it flakes off when removed and dry... but the stainless is also definitely eroding away. There is a black sludge in the bottom of the Cupric Nitrate after several etches, which I strain out and remove using mask/gloves/goggles, etc.; and I have never put the stuff down the drain, I've been collecting it in paper towels and storing in a kitty litter jug until I could take it to hazmat because I dont know what it is... Do you think this black sludge could be hexa chrome?

Some portion of it could be, but the bulk is probably mostly oxides of copper and tin. I mean lots of brass etched, vs a little bit of stainless dissolved.

You could use a test (some strips are >30$) if you are just trying to find out if you are making the carcinogenic genotoxin Chrome(VI).

I would just assume that all elctrochemical solutions are toxic.

Actual businesses doing electroetching/milling/plating can be legally quite a bit more polluting than your home shop could achieve, so this is really an exercise in being a good citizen/neighbor.

Regulations for wastewater of electro-finishing businesses in the US appear to not care about the chrome content till you are pushing more than 10k gallons of water a month or more than .58mg/l. *I am neither a lawyer nor a business consultant so your experiences with the law may vary.

Ah, well that makes sense, and no worries about the legal stuff; I'm a hobbyist and just want to keep myself safe and of course, I do not want to harm the environment either. I had not heard of "hex chrome" before seeing your post here, so I am glad to have learned about it. I think a lot of hobbyists who do electro etching (studio jewelers, mostly) do not treat these byproducts with as much caution as they deserve, because it seems benign compared to acid etching waste. Okay, one more chemistry question, not sure if you can help: I use Cupric Nitrate, not salt water, in my electro etching. Cupric Nitrate can be used again and again as long as it is strained occasionally (which is why I like it); other etchers have claimed to have restored their Cupric Nitrate to it's original "clear blue" by simply straining it through coffee filters. (Nope. The solution continues to look like muddy river water.) Do you think there is a need to strain it more thoroughly? Visually, the solution looks like it needs to be cleaned, but I am not sure if it is necessary for it to continue to serve as an effective electrolyte. I've been looking at buying a lab filtration system like this, but I am not sure if it is necessary: Thanks, you are my hero. :D

I used this method to etch a few small things (stainless steel), however, within a week or two, the etched areas were rusting. How do i avoid this????

1 reply

Hi Kimbeaux...

Your stainless steel probably has a high iron content, so it will rust no matter what.

Some stainless steel will rust, and some will not. I'm not sure which grades are which, but I'm sure you can find info on the web. There are some that will not rust.

To clean it up, check out removing rust with electricity!

Also, you can certainly spray the resulting etch with a coating of polyurethane, shellac, wax, or similar clear coating to prevent rust.

Good luck!

Tnx. its an effective tutor for me.