Acid Etching

This will be a basic tutorial on how to acid etch metal with Ferric Chloride.
I won't get into too many details on stenciling and the graphic design side of things as that would be a whole other tutorial!

Etching is a great way to personalize your knife. Maybe with a makers mark or just add some unique design to your boring EDC.

Hopefully this provides you with detailed yet easy to follow instructions on how to acid etch your knife.
I am still new to this whole etching thing and I won't pretend to know everything or have all the processes perfected, so feedback and tips are greatly appreciated.

FAIR WARNING!!! I can not be held responsible for any damages or injuries as a result of trying this process.

(But if you hurt yourself then that means you really screwed it up...)

Step 1: What You'll Need

Supplies

• Ferric Chloride (PCB etch) - Found at electronic part stores and some say Radioshack.
  Link to Ferric Chloride information
• Plastic container
• Distilled water
• Etch resist/Stencil - IE. Nail polish, stickers, vinyl, electrical tape, Sharpie marker
• Acetone
• Cotton swabs and/or Q-tips
• Paperclip and/or dental floss
• Rubber gloves
• High grit wet/dry sandpaper or steelwool

Step 2: Preparation

Preparation is the most important step in this whole process. If you don't prep properly the results will be poor and very frustrating.

• Disassemble the knife.
  You don't want to get any acid on the scales, liners, or washers. Try to remember where all those little screws came from and store them safely in a container or magnetic tray. If you don't feel comfortable taking the knife apart then ensure to mask off any part of the knife you don't want to get the acid on.
  
  
• Clean the blade with acetone. This will provide a clean surface for the etch resist to adhere to. Try not to touch the blade with your bare hands after cleaning. The oil from your fingers will mess with the etch.

Step 3: Create the Etch Resist Pattern

Get creative!

Use anything you can imagine to create a pattern on the steel.

The basic idea is you want to create a barrier so the acid can't reach the steel. This will leave a pattern when the etch resist is removed. Where ever you have exposed metal will be darkened and marked by the acid.

I've experimented with nail polish, sharpie marker, vinyl, stickers, electrical tape and different stenciling materials.

If you want the whole blade to be blacked out then very little etch resist will be necessary. Only the pivot and lock face.

If you only want a little logo then you'll want to protect most of the blade with tape and or nail polish.

SUPER DUPER IMPORTANT!!!

If you are etching a folding knife you will want to protect the pivot, detent and lock face area. You do not want to mess with the tolerances in those areas. You could eat away too much metal and totally ruin your knife.

I choose to use a bright color nail polish so I can see where it has been applied.
If you are etching liners/scales then you'll want to protect the same pivot area and the ball detent.

Step 4: Mix the Etch Acid

Put on your rubber gloves.

I mix the Ferric Chloride 50/50 with distilled water. No need to go full strength to get results. I know the website says not to mix it but we're also not using it to make custom circuit boards
Here is a link to some interesting information regarding concentrations

In your plastic container pour a quantity of water, then add the same quantity of acid to that. Do not fill the container to the top! You need a bit of space to allow for the displacement of your blade.

**Best practice is to always add acid to water. You don't want a dramatic chemical reaction or splashed acid!**

I used an old peanut butter container for my mix. Ideally I would use a container with a better lid, maybe some sort of snap-on lid. The screw lid gets messy when the dried acid crap gets in the threads.

***Label the container "POISON! ACID!"***

DO NOT mix the two together in a metal container. The acid will eat through the metal!

This mixture will last you quite a long time. Of course this depends on which metals you're etching and how much material you're stripping away.

Step 5: Ready, Set, Etch!

Ready?!

Put on your rubber gloves if you haven't already from mixing the acid.
Ensure you are in a well ventilated area. The acid is causing a chemical reaction and there is a vapour byproduct. Do this outside or under a vent/stove hood.

I will outline two processes

1. Acid bath
   I have found that short (10-60 second) dips with quick rinses under the tap gives me the best results. Use the paper clip or dental floss to dip the knife into the acid. Repeat until desired results.
   
   I do short dips because it gives me better control over the end result. This process also preserves any of the laser factory markings on the blade.
   
   My actual timeline is 10 to 60 second bath, 10 seconds in the air, rinse under the tap, 10 seconds in the air, then repeat.
   If this actual process makes any difference to the end result... I don't know. But it seems to be working for me.
   
   I also recommend moving the blade around in the acid. Others have more sophisticated systems with fish tank aerators that bubble and agitate the acid. The movement will help ensure a consistent etch with less pitting.
   Other people do one long bath in the acid. I find this eats away at the metal and it is difficult to see when enough is enough. Long for me is anything more that 10 minutes. I've done 30-40min baths but my results weren't as consistent as short soaks with frequent rinses. Again information on concentrations can be found here
   
   Be careful of fingerprints. When rinsing the blade try not to touch it with your bare fingers You may leave behind a fingerprint mark on the blade.
   
2. Focused etching.
   This works better when you're putting a small mark on the blade or only marking one side of the steel.
   
   Ensure the blade is taped off with electrical tape, vinyl or nail polish to protect the steel! I've ruined a few knives with the odd drip somewhere it wasn't suppose to be. :S
   
   Use a cotton Q-tip to soak up a bit of acid. Apply the acid to the steel in the stencil. Same timeline or just feel
   with the Q-tip for when the acid starts to "bite" the steel. Rub the Q-tip around the stencil, working the acid into the steel. The tip of the Q-tip will start to turn black as the acid removes some metal.

Step 6: Stonewashing, Sanding and Cleanup

Time to finish the knife.

The matte finish on the blade may be boring or just not quite what you were expecting.

Depending on what you're aiming for there are a ton of options from here.

• Stonewashing the blade gives it a great textured look. This is good to cover up any uneven acid etching. If you are stonewashing I recommend leaving the nail polish on the pivot and lock face. The polish will help protect these areas from any unnecessary wear.

• Others will sand down the etch to reveal a worn and distressed look to the blade. I personally use 1500, 2000, and 2500 grit wet/dry sand paper. I'm guessing 000 or 0000 steelwool would also give you a good result.

After you've gotten the results you were hoping for it's time to use the acetone and cotton swabs to remove the etch resist. This will remove any sharpie marker or nail polish that you applied to the blade, pivot and lock face areas.

Reassemble your knife and admire your handy work!

***Store your acid in the same plastic container you've been etching in***

If you're not looking to keep the acid I recommend taking it to a hazardous waste disposal facility or at least neutralizing it with baking soda. I would still recommend taking to a hazardous waste disposal facility after neutralizing as the solution has a concentration of metals that could prove harmful to the environment.

Step 7: Final Results

Hopefully this tutorial has helped guide you through the etching process.
Let me know if you have any questions :)

Your best bet is to experiment with cheap knives before you move into $500 customs.
No one wants to see a bad etch job on a custom knife!

A few last things to keep in mind.

1. The concentration of acid will change the etch
2. The temperature of the acid will change the etch
3. Different steels react differently to the acid.
4. Acid is dangerous so close attention must be given at all times
5. Drips of acid into your stainless steel sink will leave marks... don't ask
6. The acid is dark orange and will stain your skin and clothing.

Good luck and let me know how your project goes!

Comments

[Colin0750]

I've been working on restoring a wusthof kitchen knife, and I was wondering if using this method of acid etching would be a good way the bring the color back to the factory marking? If so how detailed would the resist have to be around the logo? Any help is appreciated, thanks!

[danielekellyzen]

I am etching 1080 high carbon steel, using ferric chloride, but my results are usually a medium grey, and not black. I even left one test in the acid overnight hoping time would let it work, but it still was a light grey. What am I doing wrong?

[pglazaridis]

Thank you for the detailed article.
Are all permanent markers suitable or only Sharpie?

[R_Newtron]

Thanks!
Any item that will prevent the acid from touching the blade will work.
A permanent maker should work.
I've also used vinyl stickers, nail polish, wax pencil/candle, ect.

[wyattmooring]

Your work is beautiful! (Maybe not the right word for a knife....) I am messing around with a D2 steel blade and the ferric acid seems to just turn it light gray not dark almost black like yours. Any advice?

[R_Newtron]

Thanks!
Different steels react differently to the acid. I do many (10 to 15) short baths and rinse cycles. I'll also use an old toothbrish to scrub off the slag.

[nedious]

what acid do you use and where can it be bought?

[Akinventor]

Cheap at home depot, used for concrete staining, I think.

[R_Newtron]

I don't believe that is the same thing. I think you're referring to Iron Sulfate.

[Akinventor]

It is muriatic acid and can easily be used

[R_Newtron]

Yup, Muriatic acid is another product that can be used to etch. I prefer to use Ferric Chloride because I don't want to be mixing Hydrochloric acid and Hydrogen peroxide.

[AnselmoF1]

Nice Instructable. Is there any associated dangers about mixing Hydrochloric acid and Hydrogen peroxide that we must be afraid? Mixing 3.5% Hydrogen peroxide with diluted Hydrochloric acid is very common to perform some processes (including etching).

[MacCaskill]

"Step 1: What you'll need. Supplies -- Ferric Chloride"

It's the first thing listed in the very first step.

Fry's Electronics carries it. I picked up a gallon a while back for about $20 which should last you a long, long time.

FeCl3 will etch darn near any metal including Iron and Nickel-based alloys, Stainless Steel, Copper, Brass and Zinc, to list a few.

Don't be sloppy, it'll stain just about everything brown including your skin and clothing.

[R_Newtron]

:D
All good tips

[ltnemo2000]

Ferric chloride is. Because the Fe is essentially stripped of its electrons by the Cl atoms attatched to it, the Fe becomes pretty strongly positive. So while Fe(III)Cl has no protons to donate, it can strip electrons off molecules and act as a lewis acid.

I know you can get it on eBay and Amazon. As for brick-and-mortar shops...maybe try Fry's electronics or a science surplus store? I've never seen it on a shelf.

[R_Newtron]

What Itnemo said. That is a very detailed explanation of what happens, Thanks for that!

[TaleaJ]

Dumb question; after cleanup and finishing, would this knife be safe to use with food?

[R_Newtron]

Thanks for the question. I do a light sanding to remove some of the oxidation where the acid has eaten away at the metal. I have used it for food but sometime it's leaves a... Metallic taste on the food.
You have better luck with an electro etch.

[6StringSamurai]

Hi- great information! I was wondering if this would work with chrome-plated brass. Also, if you're etching something you can't dip, can this be brushed on?

[R_Newtron]

Thank you. I don't know about chrome. I have a feeling the chrome will resist the acid.
There are a few options for applying the acid when the item can't be dipped. The item can be masked off and the acid applied with a Qtip. I've also seen some people gel the acid and apply it that way.
Check out my other tutorial on stencil etching and that may help out some ideas.
https://www.instructables.com/id/Detailed-Acid-Etching-With-a-Stencil/