As a knifemaker, I like to etch my logo into my knives. I have a pretty fancy machine to do this, however others have asked about etching and marking so I came up with a fairly straight-forward device that one can make for around $20.

But first a little background. A lot of folks etch with DC power supplies and batteries. The current flows in a circuit through an electrolyte such as salt water. The etching process removes metal from the surface of the knife and makes valley where ever the Direct Current (DC) is allowed to flow. If we apply a little Alternating Current (AC) after we etch, we blacken the etched area. This is called marking.

So the secret to an etching and marking power supply is to have both DC (etching) and AC (marking) capabilities.

Before we proceed:

A little know-how is required to complete this project. You will needs some basic tools and a soldering iron.

Please be advised that the information provided is for educational purposes only. I will not be liable for use or misuse, damages, injuries or death resulting from this information. You must also be aware that the modifications shown here will render any product approvals e.g. UL/CSA invalid.

I originally published a long form of this build on my knifemaking blog: D.Comeau Custom Knives

Best wishes,


Step 1: What You Need

With the legal stuff out of the way, lets take a look at what we need to get started.


  • Hacksaw
  • Wire stripper
  • Crimper
  • Adjustable wrench
  • Screwdriver
  • Scissors
  • Multimeter
  • Soldering iron


  • "Old style" 5 to 12 VDC adapter
  • DPDT toggle switch
  • Scrap wire
  • Alligator clip
  • Crimp type ring terminals(3)
  • Epoxy
  • Piece of plastic or polycarbonate
  • 8-32 machine screws (2)
  • 8-32 hex nut (4)
  • Small piece of stainless steel
  • Flat-head stainless steel machine screw
  • Hex nut for the stainless steel machine screw
  • Small block of wood
I made it too, thanxx to your instructables, but the blackening appears to be dark greyish.i used 9v 2amp.Tea mark in10 sec and coffee in 5 sec, n coffee i got ome patches Please suggest how to achieve perfect ink black mark and minimise duration.any change in electrolyte or technique?sendin you the snap.<br>Thanks again
I use an electrolyte solution intended for stainless steel. Also, the preparation of the surface is important, clean of any grease, fingerprints, scale etc. My timing on stainless steel is 15 seconds on ETCH, wait a few seconds, then 10 seconds on MARK.
<p>Where did you get the Electroyte solution?</p>
<p>I got my electrolyte solution from a knifemaker supply store. </p>
Hi i used salt solution along with 1.5% nitric acid,doing great ,now i got a sample of solution from outsource it taste like same but results very good means ink black on my 12v ac adaptor,it smells like a little touch of alchol.my own solution gives thick darkest brown touch not jet black.if i remove nitric acid its patchy n rough.but with same current outsorce solution doing much better.pls tell me what should i add to salt solution <br>To get fine jet black patchless results.Thanks<br>Regards:Amit
<p>Thank you for great instructions! The mark turned out very well for me using the AC/DC switch.</p>
<p>Sorry forgot to include in previous post - the mark turned out nice and dark.</p>
My adapter is not plug in and is reading cd or ac voltage :( I'm lost right now ?
<p>Ive seen that on some meters. This is usually because the manufacturer left the reference connection floating (not tied to + or - or ground)<br>If you touch your meters probes together your reading should drop to Zero</p>
<p>Wow, I have never seen that before. I'd check the batteries in the meter.</p><p>Dan</p>
In ac I'm reading Dc and in ac I'm getting DC why ?
<p>You may have the poles on your switch wired backwards. Just flip your labels and you should be fine</p>
<p>hi can i use this type of adapter ???</p>
<p>That looks like the right kind.</p>
<p>is this the right place (showing by the pencil)??? because i solder the wires to the big dots of soldering ( on the back of the transformer ) </p>
Thanks! I will try and make it
I was using this adaptor in this part that I just engrave I will make another one so that the image be black
<p>How'd you make the stencil for that one? Was it too a DIY project or did you have one made for you?</p>
<p>i have a vinyl cutter,thanks !</p>
<p>Fun little project.</p><p>Used a 7.5v DC charger with 0.7A. For some reason when I measured it turned up as 11.3vDC and 9.8vAC.</p><p>It worked though.<br>Would recommend getting something with a bit higher voltages.<br>Etched horisontal liter measurements and numbers next to them on a steel pot I use for homebrewing.<br>Took the better part of 5 minutes for etching and marking every piece.<br>Luckily the pad I used was so wide that it could cover two stencils at the same time, so I saved some time there.<br><br>It turned out ok. Some spillage where the water somehow managed to get under the tape I used to lock the stencils in place.<br>The marking was a different story though.<br>I did 4x 10seconds, with 5 seconds pauses. Barely made a mark.<br>Then I did 2x 30 seconds on top of that with a 5 seconds pause (only for the numbers though).<br>Most of the numbers turned out ok, but some were uneven.<br>Some of the horisontal lines lost all the markings after rinsing them.<br>Not entirely sure what happened there. They were all given the same treatment.<br><br>For stencils I used black electrical tape for the lines.</p><p>For the numbers I bought a pack of cardboard stencils at a hobby store, then transfered those to a map/book plastic coating (the kind you pull off a back paper and stick the transparent plastic to your book as extra protection), then cut out the letters using a very sharp fruit knife (Yes, fruit :P - it was sharper than my carpenters knife &gt;&lt;)</p><p><br>Great project though. Was fun to dabble with :)</p>
<p>Thanks for this easy and useful tool idea!</p><p>Mine wasn't as fancy as some people's here, but it sure got the job done.</p><p>It works a bit slower in brass, but I got etches deep enough in steel to add solder inlays.</p>
This is the reading I'm getting
<p>That looks great!</p>
Thank you !
<p>It should be noted that with a toggle switch, the internal contacts are opposite the lever. So when the lever is down the center and top contacts are closed. This isn't a problem as you can either label the switch based on the output (AC or DC) or you can simply rotate the switch in the hole 180&deg; to match your labelling. </p><p>Good luck!</p>
reading ac dc
Ok I notice some errors in you diagram the ac Is the (blue wires ) and the black ( dc) but in your picture of the multimeter when you are testing the blue wires you have the switch up and is reading (AC)? In the second picture you have the switch down to the black wires and is reading (DC ) ? Can you please help me I'm trying to make one but I'm lost rigth now
Great stuff thanks!
<p>done with 3d printed box and laser cut/engraved panel :)<br><br>12V, 1.2A, DC/AC switch using a relay, 3.6mm round pad</p>
<p>ops, i mean 36mm, not 3.6 </p>
Thanks for your instructables,i made that too i used salt solution,working good ,now i got a sample of solution from outsource it taste like same but results very good means ink black on my 12v ac adaptor,it smells like a little touch of alchol.my own solution gives thick darkest brown touch not jet black.if i remove nitric acid its patchy n rough.but with same current outsorce solution doing much better.pls tell me what should i add to salt solution to get fine jet black patchless results.Thanks again pls reply<br>Regards:Amit
I need to build a pad to complete the device....<br>will try it this weekend
<p>works fine</p>
<p>I apologize if this has already been covered (I didn't see it if it was), but what's more important here, voltage or amperage? I have a battery charger that is 120v AC in 2.4v DC out(I think) and 1.4 amps. Will it work?</p>
<p>My guess is that 2.4 volts is the bottom end of the useful voltage scale. It should etch but it will take longer than say 8 or 12 volts with a given electrolyte. You will want to experiment with the concentration of your electrolyte, for example adding more salt. If the electrolyte offers higher resistance (too little salt) it will required more voltage to etch properly. Also saturate your pad and tamp off the excess. The 1.4 amperes is the capacity of the charger. The current will be limited by your electrolyte. Less is cooler. Too much heat will destroy your mask or stencil.</p>
<p>So it sounds like voltage is more important, I'll just find an adapter that is better suited for the job, thank you.</p>
<p>Hi</p><p>Thankh you for the instructable, here is mine version.</p><p>As you can see I placed the switch a litle different. And it works great!</p><p>As you can see I placed the switch a litlit</p>
<p>He's that's a good idea. Now you have the switch in your hand instead of back at the transformer. Smart.</p>
<p>Thanks, and I think it was easyer in a way.<br></p>
Just tried this out. Worked great! Awesome instructable!
Thanks mate!
I made one as well. I also labeled the switch wrong. Issue I'm having is in AC mode I get huge sparks, small flame, and the stencil blows apart.. Any ideas or suggestions would be appreciated! Btw, DC, you rock man.. Love the blog
<p>That is not good. It is possible you have your mains (primary of transformer) going to the switch and not the secondary lower AC voltage. Be sure to check the output in both modes with a voltmeter before touching anything to anything. Including your body. There should be no sparking at all.</p>
Is that image of your logo done by this machine, or by the fancy one you mentioned earlier in your post? If it's made by your other machine, how can I get info on it?
<p>Yes, my logo etched in the photos above is made by this etcher as built in this Instructable. </p>
Excellent, appreciate you taking the time to respond to us. Thanks again!

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