Etching Knife Blades

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Introduction: Etching Knife Blades

About: I fix lasers for a living, love a lot of stuff (see interests I guess). Wish I had more time :D


This instructable covers how to etch a knife blade.
Modern knifes are often made from stainless steel and other corrosion resistant materials. To encourage etching electricity can be used. Don't worry, 9V is enough!

Etching is different from engraving. Engraving is usually scratching fine lines into the surface of the material, whereas etching chemically removes material, possibly until a hole is created! Etching can often go deeper than engraving.

I should mention that I got the information on how to do this from this site , it came up from a google result and gives you the basic info on how to do it. I've added pictures of my experience to help you along the way

Step 1: Materials

You're going to need:
-nail varnish (paint may do instead),
-acetone (nail varnish removed or other cleaning solvent might do),
-cotton buds,
-water,
-salt,
-a 9V battery,
-croc clips,
-a scribe or pin,
-the object to be engraved,
-a dish to do it in.

Step 2: Coat the Blade

I practiced on some cheap snap off blades and found that any uncoated material near the etching area became etched and pitted. So to be on the safe side I entirely painted the blade with nail varnish.

Step 3: While That's Drying...

Get the dish you intend to do this in (not your mum's best cookware, so scrap would be better), add the water and add some salt. You want to make salty water. I'm assuming the saltier the quicker the reaction. This might be an interesting experiment to carry out with varying concentrations of salt and measuring etch depth over a set time.
I just added a bit of salt, don't think I got anywhere near saturating the water, just enough to make it salty - a good electrolyte.

Step 4: Scribe the Pattern

Engraving is quite tricky and unforgiving.
Scribing a pattern in (relatively) soft nail varnish isn't so tough.
You don't need to press so hard you score the metal, just enough to remove the nail varnish in the pattern you want etching.
Its practically like normal writing.
If you go wrong you'll have to repaint and retry or even clean it all off and then repaint and retry.

This knife is a gift for someone who has organised our summer climbing holiday which also coincides as my honeymoon, I'm really grateful he's found us such a great place to go and organised everything so got him this knife as a thank you.

Venasque is the place we're visiting, and the year 2011.

Step 5: Electrification!!

Connect the object to be etched to the positive terminal of a 9V battery.
Apparently a PP3 square battery works fine, I didn't have any on hand but had this beefy old 12V lead acid cell. It worked great.
Connect the other end to the object to be etched. It needs a good electrical connection, don't connect it where you have painted the nail varnish, the hole point in the nail varnish is to insulate the blade and stop the electrical connection.

Step 6: Etch

Connect the cotton bud to the negative side of the battery (cotton buds aren't conductive so make sure to connect to the end you will be using).
Submerge the nail varnished and patterned part of the blade in the salt water and gently rub the cotton bud over the patterned area.
You should see lots of tiny bubbles as the electricity flows through the salt water and corrodes away the blade where you have marked your pattern in the nail varnish. Everything else on the blade should be safely coated in nail varnish and not react.

In my experience less is more. The patterns I hung about on in the water and tried to make deeper ended up messier and ill defined.

Don't reverse the polarity (negative to the blade, positive to the cotton bud). This produces more bubbles but no etching and appears to life the nail varnish which you so carefully scribed.

Step 7: Clean


a bit of acetone will easily remove the nail varnish when you think you've etched deep enough.


Step 8: Voila


the finished item could look something like this...


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    41 Comments

    ... melted wax is a good tip ... sticks perfectly ... can be removed with moderate heat (i.e. hair dryer) and re-used ...

    Before there was nail polish acid etchers used wax. Much easier to scribe trough and remove when done. Is there a reason wax could not be used?

    1 reply

    No I don't think so. I suppose just experiment on some scrap material to see how it performs. If it doesn't adhere to the steel as well as the nail varnish you might get tatty edges but I'd love to see the results. Next time I want to etch something I'll definitely try wax. Thanks for the suggestion

    That works very well if you get a clean transfer of toner.

    Nice one, that looks really smart

    On the knife that says "Velasquez" it looks like the etching is darker than the one that says "Alice". How did you achieve that?

    1 reply

    Left it in/applied electricity for longer, that and perhaps the salty mixture was fresher. Like I said though, less is more. You get a cleaner better defined etch from less time in there. You can see the q and the e in Venasque have bled a little where the resist (nail varnish) has come off. I guess if it was a very simple design or you didn't mind the edges becoming tatty you could leave it in for longer but for fine text I definitely preferred the neater shallower etch on "Alice". The photo doesn't really do it justice.

    Regulated 12v power supply 13.8V 2.5A, Salt and red wine vinegar solution, Qtip, Nail polish,Aluminum toothpick, to draw designin nail polish, 20 sec per area that head of qtip covered

    awessome idea i'm gonna do it right now!!!
    do you have to apply that voltage or you could do that with a car 12v battery? can u use more or less current? and what are the results os changing the voltage?
    thx

    How long did you rub the cotton bud over the etching area, 30 seconds, 1 minute, 10 minutes?

    3 replies

    I did it for a minute or two maximum, as I said in the instructable, the best result were from less time. Less is more. Doing it for longer meant the nail varnish degraded round the edges a bit and the whole thing got tattier and ugly. Less time gave a sharper image, though not as deep.
    I'm afraid you really need to experiment for your self as I haven't specified amount of water to amount of salt ratio, nor do I know which battery your using I can't be more specific. All this will affect how long you need to do it for.
    It certainly shouldn't take as long as 10 mins.

    So etching out say thin intricate designs completely from the metal is very unlikely?

    I take it your referring to eating right through the metal?
    I guess you could but I think you'd have poor resolution. If you can imagine the nail varnish resist only work on the surface. Once you've eaten in to the metal a little, the side walls of the trench you're etching aren't protected by the resist. This would allow the edges to eat away, possibly even undercutting the initial design.
    If you're trying to do it to something very thin it might not be a problem but I suspect anything over about 0.1mm is going to show noticeable pattern degradation. Experiment I guess.
    Also don't forget the middle will drop out of characters like a, e, o, p, d, 0 etc.
    You'd have to have supports like when you stencil

    Tried this last night and I was very impressed. However I used a an old FRS radio wall wart (7.5v, don't remember the amps) instead of a battery.

    Very cool. Thanks!

    3 replies

    Let me clarify a few things here. I am very weary of the danger here and, as such, took a few precations. I never touched the water. Also, I insulated the metal being etched and the cotton swab with electrical tape where I was holding them. I have no desire to be shocked. :)

    I'll check on the amps when I get home tonight and let you know.

    worried about the "danger" from a 9V battery? really?!

    I'm a little late to this discussion but just recently came across this thread and thought I would add my 2 cents.

    Typically the ESD (electrostatic discharge aka ‘Static Electricity’) 'human body model' testing is 8,000V touch and 15,000V air gap. This is used to test electronics for susceptibility to ESD. You rub your feet on the rug and zap a sibling... that's a very respectable amount of voltage that you just generated.... but there is essentially no current and "Current Kills"... It only takes something like 6-20mA (don’t recall the actual amount) through the heart to kill. Wall warts typically supply 250mA to 2A. Batteries will source all the current that they can. As long as there is minimal resistance along the path of electricity and you send 20mA through the heart... DANGER is possible. Using an electrolyte rich fluid (like salt water) and placing your hands in a bad way, it could very well put you at risk. Granted your skin will act as impedance... but it all comes down to Ohm’s law.

    What I think ‘_soapy_’ and ‘laserage’ are discussing further down is if a bad setup is there and the cheap little wall wart is past its nominal operation… it could have problems and source more power than a battery could. Given how cheap those things are, that is definitely a possibility.

    Like I said, my 2 cents... ehh maybe my 1.5 cents. =)