Introduction: Electrolytic Etcher

Picture of Electrolytic Etcher

I did some electrolytic etching when I made a crossbow, this was a very rough and ready affair where I simply used a saline bath, two wires and a 12V battery. I was pretty happy with the results and so, I did a little bit of research into electrolytic etching and I got to wondering about making a dedicated etch driver.

The idea was a simple one, take a 12 Volt AC Adapter add in an on-off switch, an indicator light, a potentiometer to "tune" the output voltage and a couple of alligator clips on leads.

Another goal was to make it look attractive, so I wanted to make a custom instrumentation panel that had a steam-punk feel. When I got it all working, I would like to rework the project box in timber and make it look more steam-punky.

Simple goals, really ... still it took me quite a long time to find the time to actually complete the task.

The Electrolytic Etcher project is:

  • part electronics project
  • part tool maker project and
  • part artwork

Step 1: How Does It Work

Picture of How Does It Work

The picture above should have a 6.8V DC source, rather than AC.

The principals of Electrolytic Etching are the same as with acid etching, however, with electrolytic etching, the atoms are separated with electrons, rather than chemicals.

You can use some pretty safe voltages and the mordant is reasonably safe (salty water) so there is far less risk to your person using this method that using toxic chemicals. Safety should still be observed, the process releases gasses. While the gasses that are released are fairly benign, you should still do this in a well ventilated space.

OK. So … the electricity source. My 12V battery charger is nowhere to be had, and I don’t want to buy another one. The solution? Make one.

I still have a large number of old mobile phone power adapters with a power output range of 5V through to 12V. I don’t need anything as powerful as 12V … so I am using an old power adapter (for something … I can’t remember what it was for … a charger for something that I don’t have anymore).

I want to be able to regulate the power, so I’m going to wire it up to a potentiometer. I also want to be able to switch it off … so a SPDT (single pole double throw) switch will do the trick. I have some parts from other electronic projects, so there isn’t much that I need to buy.

The parts list for the power supply are as follows:

  • 6.8V AC Adapter;
  • SPDT toggle switch;
  • 330Ω Resistor;
  • 3mm 5mA Red LED;
  • 10kΩ potentiometer;
  • tuning knob;
  • PCB perf board;
  • 2 x banana plug sockets;
  • 2 x alligator clips attached to banana plugs;
  • red and black multi-strand wire;
  • 130 x 68 x 44 mm jiffy box

(the idea for this power supply came from NavaChing – Etching, although I have modified the design to suit my purposes … I don’t plan to run the etcher from batteries).

I have some testing and soldering to do first, so I’ll post some pictures later when I get the device working.

As I have mentioned in other posts, I’ve had some success with electrolytic etching steel previously, but this time I want to etch brass so I’ll walk through the process in some detail so that others can benefit from my mistakes.

To recap on the process … design, print, transfer, remove paper from work piece, connect work piece to the positive (+) rail, connect a conductive piece to the negative (-) rail, immerse work piece and conductive piece in salty water, power up, bubbles and etching happen, power off, clean work piece, enjoy your success.

Step 2: Wired Prototype

Picture of Wired Prototype

Here is the wired solution. SPDT, Potentiometer, banana plugs attached to

alligator clips and using a lamp to test the voltage output. I haven’t heated the shrinky on the AC lines yet, because I will need to resolder them into the jiffy box, and adding the shrinky to the connection at this stage will just be a pain in the arse.

I got the Retro knob from Jaycar.

The SPDT toggle switch came from an old project. I’ve only connected COM and Leg 1. In this configuration, it is a simple On/Off switch.

And here it is turned on. The left image is the lamp when the pot is at about
60%, the right image is at 100%. When the pot is dialled less than 60%, there is little to no light coming from it. I’d say that that is because of the minimum voltage required by the lamp. By the way … having a lamp like this is a good test tool for making sure that you are getting some power.

The next steps for this project are to:

  • Put the circuit in the jiffy box;
  • Make an etched plate for the jiffy box with labels for the dial, power and the two banana plug sockets;
  • Maybe add an LED to indicate power.

Well … apart from that, it’s job done. I’ll be using this driver in later articles showing it in use. The first article will be making the etched plate for the driver! I’m going to do that with a scanned, hand-drawn image, something a little bit steam-punk.

Step 3: Fit the Electronics Into a Box

Picture of Fit the Electronics Into a Box

I fitted the electronics into a project box so that the electrolytic etcher is all packaged up and ready to use.

I also added a LED power indicator into the circuit. After doing some testing, I discovered that my old LED was indeed dead, so I added a brand new LED lamp to the circuit as per the design shown in the previous step. The LED doesn’t show up very bright in the photograph … but it is there and it does work

I am using a 5 amp globe to demonstrate that the power is indeed flowing through the circuit and that the potentiometer does indeed regulate the flow.

The images shows the project in the box plugged in, but switched off; switched on but potentiometer at 0% and switched on an potentiometer at 100%.

I still want to make a top panel for the project box with a dial indicator, switch and power labels and positive and negative labels.

I’ve drawn up and scanned the basic design that I will etch into the top panel. I plan to do a bit of tinkering with the design for the top panel yet. But this is what it will look like.

The plate will be etched in brass and I think that a nice copperplate font will be good. I might put a kind of cogs and wheels design into the ground area for interest … I’m not sure yet.

Again, I can’t stress this enough, this is a simple design and has been pretty easy to build and test. I can only estimate the total cost of the project, because I had the power supply, switch, wire and solder already on hand. My out of pocket expense for the project was $14.00, getting the parts from Jay Car. If I had to buy the adapter and the switch, it would probably have increased the cost by about $20. Although, you could do better than that if you sourced your supplies from eBay.

Step 4: Panel Design

Picture of Panel Design

Now we get on to the arty side of the project ... an instrument panel for the top of the Electrolytic Etcher.

I’m going to go through the design, transfer and then the etch of the instrument panel for my Electrolytic Etcher. I’m going to be using the Electrolytic Etcher that I made in the previous pages.

To start with, I measured the top of the project box. This comes in at 13cm x 6.6cm. I’ve taken off 2mm from each side to accommodate the rounded top of the box, so that the plate doesn’t extend over the rounding.

I made a basic design in the previous article so that I could work out where to drill the holes for the various parts of the device.

Now, I want to add some design elements to the panel.

I’ve used Photoshop to do my design work. I also make heavy use of guides in Photoshop.

I scanned the original, hand-drawn layout at 600 pixels per inch. This size means that I have a good resolution to work with. The down side is that it turns out to be a fairly large file (about 17Mb). Still, hard disk space and memory are cheap, right?

You’ll notice that I’ve also left a fairly generous border around the image (Document Size).

Once I had the scanned image, I cleaned up all the messy bit’s from erasing lines. Did some rotation of the image so that it was lined up properly in Photoshop, then I replaced the hand drawn bits with clean lines and layers.

I split the image into:

  • field;
  • border;
  • dial;
  • through holes;
  • labels (individually);
    • Terminals;
    • Power LED;
    • Switch;
    • Numerals;
    • Panel Title.
    • Drill Guide

The numerals around the dial were then placed and I made a new layer under each number with a white circle with a black border. To make the circles, I first created a black filled circle and then contracted the border by 4 pixels and filled it with white. I do this for all of the other labels (except the panel title).

For the Off/On switch, I made the text panel by creating two circles, adding a rectangle and then subtracting the circle in the middle for the drill guide.

For the panel title, I added the text, copied the text layer and rasterized it, selected the rasterized layer and expanded the border by 14 pixels and filled it in black. Then I contracted the border by 4 pixels and filled it with white. Finally, I removed the small holes in the text that were made when I expanded the rasterized text.

Then I started playing with the field. I wanted a pattern in the field that sits behind the text, dial and drill guides.

I started with a black and white leather texture pattern.

I also tried a steam punk black and white repeating pattern ... but it was a bit busy.

When I transfer the image to the brass plate, the image will be reversed, so I need to reverse the artwork so that it comes out the right way.

First I make a copy of the Photoshop file so that I have a backup. Next, I flatten the visible layers. Then, I flip the image horizontally.

When I etch, the bits that are white will be the bits that are etched … the bit’s that are black will be protected by the toner ink. So I need to invert the colours.

There’s a whole lot less that will be etched (around about 35%), so the etch won’t need to take very long to get a good bite.

Well … that’s the design process done. Next, I’m going to print it out and transfer the image onto the brass.

Step 5: Etching the Instrumentation Panel

Picture of Etching the Instrumentation Panel

I had transfer printed the instrument panel ages ago and I just never got around to doing the etching. Ironically, because of the way that I designed the panel, the only satisfactory way to etch it was using acid. I used the same acid that I normally use for printed circuit board etching (hydrochloric acid x 1 : hydrogen peroxide x 2).

After etching the brass, I gave it a bath in cider vinegar and salt and then cooked it for a short while (about 10 minutes) … the baking paper started to smolder and it set off the smoke alarm in my flat.

Next, I rubbed some blue and green paint into the surface to flood fill the etch and give me some contrast. It may look like a crap colour, I’m colour blind, so I won’t be able to gauge the “patina” until I can get someone with better colour vision to assess it.

The contrast is satisfactory and I think that the colour is OK too. I can read the panel, so it does what it needs to do.

I’m taking it home this weekend so that I can drill out the holes where the switches, plugs, power indicator LED and potentiometer come through the panel. Most of these bits of instrumentation will be used to hold the panel down to the project box.

It’s a bit of a pity that you can see the lines where the texture tiles fit together, maybe I’ll go over it with the Dremmel to “blur” the lines a little.

Overall, from design to finished panel has been a bit of a long journey. I really don’t think that I’ll need the etcher now. Still, it will also work to drive a polystyrene cutter (6.8V) and there isn’t anything that I need to change with the Etcher to make it work … just add some NiChrome wire between the Anode and Cathode, and we’re away.

I reckon that it looks suitably Steam Punk in design, so it fit’s the bill there. I may need to do some more work on the rest of the project box to make it look more Steam Punk … maybe replace the box altogether with an antique timber box, or I could make a timber box and give the box a Steam Punk feel.

Step 6: Using the Etcher

Picture of Using the Etcher

My process needs some work, so please feel free to do whatever you want ;)

These are the steps that I used when I was attempting to etch the instrumentation panel.

I had some problems with my resist and the power needed to be tuned properly (it was too high).

The process, however, is sound.

Add a resist to the parts that you don't want etched. Using Toner Transfer method to apply the design to the face of the plate and then an acid resistant paint was applied to the back of the brass plate.

I put a bunch of marbles into a plastic container so that there would be plenty of space for water flow in the bath.

The water/salt solution was added to the bath and the anode attached to the work piece while the cathode was attached to another piece of brass that was immersed into the bath.

When the power was turned on, the bath became murky from all of the ionized brass coming off the work piece.

I ended up with a faint bite because my power was too high and my resist was rubbish.


eruger (author)2015-03-11

By the way, I find slotted screws better for the steampunk look, since cross-slots were rare prior to the Phillips, (which was invented in the 1930s) and not common until a while later. If you have trouble finding slotted machine screws, Amazon has them in a variety of metals, though you usually have to buy a bunch at once. Try it. Your stuff will look older instantly.

baelza.bubba (author)eruger2015-03-12

Thanks eruger, yeah, I'm OK with period fails ;) Actually, I've started making my own fastners from brass rod and hex tubing, so I'm going to go with more visible rather than period. Then again, after making a few I might just give it up as a game of le bugers risible.

eruger (author)baelza.bubba2015-03-12

Hey, it's art :) Whatever suits, (though hex head screws have actually been around for centuries). Square heads are fun too. Or you can put a truss head screw in a coupling nut to hold it and grind it into a slotted hex in a jiffy, which looks nice. But what matters is if you like it :) How are you doing the thing with the hex tube? Soldering?

baelza.bubba (author)eruger2015-06-15

Hi eruger, sorry ... I missed your question. Yep, soldering. Basically, cutting a 5mm section from brass hex tube and 17mm from a brass solid rod (snug fit inside the hex tube. Applying some flux to the rod, putting the two together and soldering. When it's soldered, I then shape the head to a slight dome shape and polish. The silver solder shows in the head ... I'm considering using the etcher in reverse to then plate the head with copper for a more consistent finish ... I've made a couple for some light fittings where the old bolts had "disappeared".

u000tbm (author)2015-04-15

Please insure that your power supply has a transformer to isolate you from the AC house mains. Some cheap adaptors do not have a transformer, and connecting the hot to any body of water would be bad.

baelza.bubba (author)u000tbm2015-04-15

Good point u000tbm, safety first!

jscanlan (author)2015-03-09

The kind of salt you use will effect the etching action. Copper sulfate is very active all by itself on aluminium and fairly active on zinc, I don't know how it would work on iron or steel. My Brother laser printer does not do transfers very well. Will way darkened copy machine copies work better?

baelza.bubba (author)jscanlan2015-03-09

Hi jscanlan. Mostly I use good old table salt for etching. Other types of alkalines would be used in plating, rather than etching. I use a Brother HL-2130 that I bought for $50. I don't jigger around with the darkness settings at all but use reasonable quality paper. Maybe you're not ironing it for long enough or your iron isn't hot enough? It's hard to say without seeing the result.

eruger (author)baelza.bubba2015-03-10

Do you get the foul fumes some other people have griped about with the table salt? I wonder if it's the iodine?

jscanlan (author)eruger2015-04-05

You get hydrogen and chlorine gasses. Hydrogen is very light and will diffuse very quickly, so it is only a danger if you use a lot of power and confine the gas. Chlorine is nasty, it was used in WW1 as a weapon. Do this etching in a very well ventilated area, if the smell gets strong shut if down and leave the area.

eruger (author)jscanlan2015-04-06

Good advice. Don't worry, I'm quite aware of the dangers of chlorine gas, but thanks for being sure :)

bpark1000 (author)eruger2015-03-10

It is chlorine from the sodium chloride, If chlorine is coming off, the anode (work) current density is too high. You want the current to be stealing electrons from the metal to be etched, not the chloride ions from the salt. Fizzing should be only taking place at the cathode, that is hydrogen.

eruger (author)bpark10002015-03-11

Thanks! Is the hydrogen from electrolyzing the water? That's another thing to be careful of then. I like my eyebrows.

bpark1000 (author)eruger2015-03-12

Unless you are slamming in 100's of amps, you need not worry about the hydrogen. Running at 1 amp, you make about 1 gram of hydrogen in a day (that would be around 10 liters). As long as you don't take steps to confine the hydrogen, it will diffuse away as fast as it is made, and your eyebrows will remain intact. What is worse if you do this a lot: The hydrogen fizzing out throws tiny droplets of the electrolyte into the air, which settle on things and cause corrosion on metals in the room (like "salt fog" near the sea).

baelza.bubba (author)eruger2015-03-12

According to Wiki "Anodic etching has been used in industrial processes for over a century. The etching power is a source of direct current. The item to be etched (anode) is connected to its positive pole. A receiver plate (cathode) is connected to its negative pole. Both, spaced slightly apart, are immersed in a suitable aqueous solution of a suitable electrolyte. The current pushes the metal out from the anode into solution and deposits it as metal on the cathode. Shortly before 1990, two groups working independentlydeveloped different ways of applying it to creating intaglio printing plates."

You get both Hydrogen and Chlorine gas from the process. It's all sciency-wiency, so I ask my wife (who is a scientist).

baelza.bubba (author)bpark10002015-03-11

Yep, stinky chlorine gas (and dangerous). That's a very good point ... best to do this (like most other projects involving etching) in at least a well ventilated area!

bpark1000, you are a legend

MandingaRes (author)2015-03-14

Honestamente no conocía el grabado de metales con agua salada y el método de la electrolisis, solo sabia que se utilizaba para disociar moléculas, así que te agradezco el informe porque me ayuda a seguir investigando sobre el tema. Ya comencé por NavaChing - Aguafuerte (por cierto página bastante rara..) y seguiré con otras. Gracias

baelza.bubba (author)MandingaRes2015-03-14

Hey MandingaRes,

You're welcome. The salt water electrolysis process is pretty simple (and old). Good luck in your studies. I read the Navaching page ages ago, it's one of the places that I started with the idea of making my own with a DC adapter.

hipatetik (author)2015-03-12

Interesting. What about designing a tool for a CNC engraver using this principle?

poundchannel (author)hipatetik2015-03-12

I'm in the process of building a multi-tool CNC based off of Inventables' X-Carve; I don't think it would be terribly difficult to do. bpark1000 made some good points and I need to research proper etching techniques more though to be sure.

baelza.bubba (author)hipatetik2015-03-12

I'm not so sure that electrolytic engraving would be controllable by CNC, other than setting the voltage ...

ChEM (author)2015-03-10

Nice one mate.
Good information and documentation, and the brass panel looks really cool, too.

(off topic)... Where did you find your little blue monster (Grendel?) user picture? I once had it in a book of fantasy artwork, but have never been able to find it since.

baelza.bubba (author)ChEM2015-03-11

ChEM, it was from the Tourists Guide to Transylvania, a compilation fantasy/horror art book. I suppose he's a little Grendel like, but the artist simply called it a "Demon". I've got the book packed away somewhere from my last interstate move, so I can't give you any definitive intel.

Page 40 - Artist: Melvyn - Choronzon, the Dweller in the Abyss ... found the book ;)

ChEM (author)baelza.bubba2015-03-12

Thank you so much!
You've no idea how long I've been trying to find this out! (years and years and years... I kid you not!)
How very kind and considerate of you.
You've truly made my day!

baelza.bubba (author)ChEM2015-03-12

You are very welcome ChEM

bpark1000 (author)2015-03-10

You need to control the current density (amperes per square inch) to get the etching to work right. You need to know roughly the area you are etching. You also need to set up the geometry so the etching current is evenly distributed over the area to be etched. For example, for the panel you show in step 6, apparently you have the side to be etched facing up. It should be facing, and be parallel to, the cathode, which looks like it is underneath. The cathode should be at least as large es the surface to be etched. (If you were etching the inside or outside of a cylinder, the cathode would also want to be cylindrical, facing the side to be etched). The solution is selected depending on the metal etched. For copper, I would use well-diluted hydrochloric acid. You should have an ammeter so you know the current. You can also use a regulated lab supply. A 10K pot is way too high. Current wants to be in the range of up to 1 amp per square inch, so the current should be in the range of, say, 1/4th amp for small stuff, and 2-3 amps for large panels such as you have.

I would put the work on the bottom, etched side up, and the cathode on top, held by plastic spacers. (if you make cathode larger then work, it could have 4 nylon standoffs at the corners, and rest on the tray bottom like a table). Use no marbles, you need free circulation of the solution. The cathode will fizz with generated hydrogen. If cathode is perforated, the hydrogen will rise through it, staying away from the work below. A quick and dirty way to make test pieces is to use diluted nail polish as a resist, hand-painted on. experiment with the current density until you get things to work right. Current too high, the work will "burn" and the resist may fail. Too low, you will need a century to do the etch, but it should be OK.

excavatoree (author)bpark10002015-03-12

Would changing this circuit to a constant (adjustable) current work better? Use a LM317 or other constant current circuit and set the output current based on the area?

baelza.bubba (author)bpark10002015-03-11

Thanks bpark1000, those are some great suggestions! I'm going to have to do more play with my toys now ;)

declanshanaghy (author)2015-03-10

Why did you end up having to do a chemical etch as opposed to an electrolytic etch?

Hi declanshanaghy, the main reason was that I was running out of time and I had an acid bath handy. I was moving from state to state at the time and I had to make the plate in a different state.

Ahh, ok. I assumed it was a technical reason.

lol ... no ... not technical

sgiane (author)2015-03-10

Very insteresting. I'd have a couple of noobie questions, please:
> Any problems if I use a 18v power source ?
> Does the polarity matter? i.e., positive (+) must be connected to the piece?
Thanks a lot.
Great job.

baelza.bubba (author)sgiane2015-03-10

Hi sgiane, I wouldn't recommend going over 12V. The circuit doesn't have a fuse or a heat sink.

Polarity certainly matters. Check out

The process is, to put in simple terms, pushing the atoms away from the metal workpiece (anode) and pulling them toward the negative current (cathode) through an electrolyte (the salt water bath).

sgiane (author)baelza.bubba2015-03-10

Thanks baelza.bubba! :)

baelza.bubba (author)sgiane2015-03-11

You are welcome, sgiane

mdeblasi1 (author)2015-03-10

Thanks so much for the Instructable,
I have been setting aside some ideas I have for etching, but procrastinating because of the mess with the acids.
I'm not really good at putting images of my work up, but if I get it running in a reasonable time, I will post an 'I made it' as a thank you.

eruger (author)mdeblasi12015-03-10

I have been in exactly the same position. I've been procrastinating because it's so hard to ventilate in my apartment and be sure I won't be gassing a neighbor.

baelza.bubba (author)eruger2015-03-11

Procrastination is putting off today what you don't intend to do tomorrow ;) A perfect circle of never-mind over don't matter.

I am a master of procrastination, it's what you learn most adroitly from years of study.

baelza.bubba (author)mdeblasi12015-03-10

Thanks mdeblasi1 :) I'll look forward to that!

eruger (author)2015-03-10

Btw, your so-called 'crap color' looks fairly well black in the photos, and it looks great!

baelza.bubba (author)eruger2015-03-11

Thank you eruger, you're too kind.

profpat (author)2015-03-10

Good day to all, 10k carbon type potentiometer will burn easily. You may use an ac light dimmer, connect the ac light dimmer to the ac side of the-6.8v adapter, remove the 10k pot and replace it with the light dimmer control, this way you are adjusting the primary voltage of the adapter which will also adjust the 6.8 Volts secondary dc voltage. For faster etching time, I would suggest using 12volts 3amps power soure or a motorcycle battery n

baelza.bubba (author)profpat2015-03-11

Another great bit of info. Yes, the AC dimmer would work well on the AC side of the circuit.

eruger (author)2015-03-10

If I use a small incandescent (flashlight bulb) then I shouldn't need the resister right? (I'm kinda rusty at building circuits).

baelza.bubba (author)eruger2015-03-11

so long as the bulb can handle the load, yes. In the test circuit, I use an 8 ohm incandescent lamp.

rpotts2 (author)2015-03-08

Can't the same circuit be used to deposit metals, like chroming something?

Arx (author)rpotts22015-03-10

The circuit would probably work fine, but you usually need to use some nasty chemicals to get plating that actually sticks.

I've done electroetching of copper, using copper sulphate, and a copper anode. In that case, the copper didn't really build up at all, I just got a fuzz of copper loosely stuck to the cathode where it could be easily scraped off.

eruger (author)Arx2015-03-10

It art school, we cleaned the heck out of the metal to prevent that, first with detergent, then with pickel, then with distilled water rinse. Seemed to do it. However, the instructor never let any us plate anything but copper (yes there are reasons to plate copper over copper) or certain plastics with certain coatings, all of which she supplied, so that could be a factor too.

About This Instructable



Bio: I have been working in IT since the mid 1980's. Most of that has been database and application development. I've been working on ... More »
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