Tag Archives: apple cider

Acid Etching With Ferric Chloride and Apple Cider Vinegar – Wicked Results on High Carbon Steel

I recently did two posts about building a new heated tank out of PVC pipe and a digitally controlled heating element that is both effective and affordable. This also marked my first batch of blades where I moved from my traditional hot apple cider etching to using a mix of 70% ferric chloride and 30% apple cider vinegar heated to 90-94F.

The Chemicals

Let me give you a quick overview of the two chemicals I used to make my blade etching solution:

The primary ingredient is liquid ferric chloride from MG Chemicals. It’s available in quarts and gallons and is about 38-42% ferric chloride by volume. The MG Chemicals product is well regarded and that played a big factor in my selecting it. I purchased mine from Amazon and it arrived quickly and well packed.

The second chemical is regular apple cider vinegar from the grocery store. They tend to be normalized around 5% acetic acid by volume. The brand I used was at 5% and there were other brands at 4% that I passed over – go for 5% because you need the acetic acid. I literally bought this at my local grocery store – nothing special.

The solution I made was 70% of the ferric chloride and 30% apple cider vinegar. I wore lab goggles, nitrile gloves, old clothes and am in a well ventilated area when I slowly add the ferric chloride to the relatively weaker apple cider vinegar.

The ratio was based on looking at the end results from other blade smiths and talking about what they learned. In my case, I can tell you that this combination makes for a very nice dark etch.

The Process

  1. Heat the etching solution up to 90-94F before I put in the first blade. MG Chemicals recommends the operating range from 94F to 131F and not to exeed 131F. [Click here for their technical data sheet and MSDS]
  2. The blades need to be at least 70F prior to dunking in the solution. The warmer the solution and blade, the better chemical reaction you are going to have.
  3. Clean the blade with brake cleaner throughly
  4. Abrasive blast the blade – I am using Black Beauty these days. It is a coarse coal slag based product. Note, not all guys blast their blades – some just clean them very carefully.
  5. From this point on, wear nitrile gloves when handling the blades to avoid any oils and contaminants from your skin
  6. I again use brake cleaner to do a final cleaning and make sure it fully evaporates. Some guys rub down with acetone – do what works for you but it must not leave a residue
  7. Fully submerged the blade in the heated etching solution for 10 minutes
  8. Remove the blade and wipe off the remaining solution with a paper towel [as a reminder, you must be wearing gloves to not contaminate the blade]
  9. Used clean/bare 0000 steel wool to buff the surface of the blade and remove any loose particles. Note, this 0000 steel wool is bare wool – no cleaners or anything. You find these in woodworking / hardware sections of stores – not in the kitchen area.
  10. Submerge the blade for another 5 minutes and again wiped and rubbed the blade down with steel wool. I think I repeated this process three times per blade but experiment and see what works for you.
  11. Soak the blade in warm water with baking soda to neutralize the acid
  12. Spray the blade down with WD-40 to displace the water
  13. Apply finish – I like to use a 50-50 mix of boiled linseed oil and turpentine to apply severa thin coats. This gives my blades the worn post-apocalypse look. Many guys just coat the acid etched surface with oil to inhibit rust.
Here’s a small 5″ khukuri where all steel surfaces have been blasted.
Here’s the finished khukuri just before I mailed it to its new owner.
Here’s a look at the solution in the tank.
Here is one of the etched damascus blades. The beads on the blade are oil.
Here’s an even closer look at the finished blade.

Summary

I’m definitely very happy with the results and will be using this solution going forward.


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Acid Etching Steel With Apple Cider Vinegar

Some folks have asked how I get the dull grey look on khukuris that I used to work on.  The answer is simple – apple cider vinegar straight from the grocery.  I’ve also experimented with various ratios of Prep-and-Etch, which contains Phosphoric Acid, and gotten a darker color but apple cider works remarkably well.  Apple cider vinegar contains 5-10% acetic acid (CH3COOH) depending on how it is made.  For example, I read that Heinz is about 5%.  My local store carries Spartan brand, which is their store brand, and it works just fine – again, this is apple cider vinegar from the grocery store.  

This process only works with steels that can rust.  For example a mild steel or high carbon.  It will not work on stainless, aluminum, etc.

Safety Notes:

I would recommend doing this outside or some place very well ventilated or else if the acetic acid condenses on metal surfaces in your shop/garage, it will cause rust.

Wear safety glasses and don’t goof around with the stuff.  I’ve never had a problem but probably need to say some kind of warning here.

Process:

  1. Clean the part and remove all oil and grease.  Either hose it down really well with brake cleaner or soak it in acetone.  Any oil, even from your skin, will mess you up.  
  2. Abrasive blast the part – I use “The Original Black Beauty” media that I get at my local farm supply store.  It’s made from coal slag and is fairly environmentally friendly.  It does break down quick so if you use your blast cabinet a lot, be prepared to clean it out and add new media when performance starts to suffer.  Blasting will get you a really nice uniform surface color.  I suppose you could try sanding or wire brushing but blasting has worked the best for me and is all I do now.  My only recommendation is not to use sand because as it breaks down it creates a fine dust that will never come out of your lungs – read that as “bad”.  I do use a blast cabinet with a vacuum to get rid of dust, you could do this outside with a hand blaster or tank blaster and dust mask if you needed to.  I wear a hood when blasting outside as the media goes everywhere.  Just protect yourself is the bottom line.
  3. Wear rubber gloves and clean the part again – the gloves are to keep oils from your skin from contaminating the part and preventing etching.  Cleanliness is critical.
  4. Put the part in cider that is at least 70 degrees.  I like 100-150.  If it is too cold the reaction slows waaaaay down.  I don’t like to get it super hot or boil it as you lose a ton of cider with no real benefit.  I have done this in everything from stainless steel containers to plastic containers and even plastic trays used for wallpaper with halogen lights warming it up.  In general the colder the cider the slower the etching and the hotter the cider the faster the etching bearing in mind you will have the cider evaporating faster.
    Note:  If you do not see bubbles coming off the part then either the solution is too cold (especially on cold days under 70F), the part is not clean or ready (so clean and blast it) or the cider too weak.  I’ve never had an issue with weak cider – always the first two.
  5. Submerge the part in the acid and let it sit for 15-30 minutes.  It’s not a strong acid so there’s no rush.  Just check the part and stop at the color you want.
  6. Rinse with hot water
  7. Rub down with WD40 and steel wool to get the loose particles off
  8. Then I like to seal it with boiled linseed oil (BLO).  Some of you may know BLO for woodworking but it is an old school rust inhibitor.  If you don’t want BLO, then thoroughly oil your part.

I like the results.  No real harmful chemicals are used, it’s cheap and looks great.

3/4/2020 Update: I recently did some blog posts on building a cost effective digitally controlled heat tank from PVC pipe that is perfect for acid etching – click here for that one. I’m also using a ferric chloride and apple cider etching solution now – click here for that one.

Photos:

The light brown solution is just apple cider.  If it is darker, it was 25-50% Prep-and-Etch + the vinegar.


You can usually get a coal slag blast media very, very cheap from farm stores.  Check there first because off Amazon you are paying a pretty penny for shipping whether they bury it in the item’s price or call it out separate.  I think I pay $7-9 per 25# bag at Family Farm and Home.

This is the actual product I use:  http://www.blackbeautyabrasives.com/products/black-beauty-original-abrasives.php

Now for the blasting, you have tons of options – hand blaster for small work, siphon blaster, pressurized tank or cabinets.  It all depends on how much blasting you plan to do.  I started out with a siphon blaster – dirt cheap but very slow.  I then got a tank and it was very fast and portable but media went everywhere.  I still have that for working on cars and big parts.  However, for my grips, gun parts and knives, I use my blast cabinet.  I have a Cyclone brand large bench unit and am relatively happy.  If I had it to do over, I would have gotten a free standing unit with a bigger and deeper hopper so I’m not constantly hitting the side or moving media around by hand.  I have a foot control pedal and that really helps plus it gets a the pneumatics out of the cabinet where they would normally be subject to abrasive dust and wear.

Cyclone Manufacturing
http://www.cycloneblasters.com/

My pressurized tank blaster is a Harbor Freight unit.  It’s held up relatively fine other than my constantly wearing out valves and tips.  The tank itself is just fine.
http://www.harborfreight.com/40-lb-pressurized-abrasive-blaster-68992.html


If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at info@roninsgrips.com.


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