Hello dear Stemians,

today I want to talk about hamon (刃文).

You've probably seen it on some of my knives, and a lot of people have asked me what it is and how it's done so here it goes.

Basically, hamon is a visual effect of a differential heat treatment, where the blade is quenched in such a way that the edge is hardened and the spine is left relatively soft.

The hamon outlines the transition between the region of harder martensitic steel at the blade's edge and the softer pearlitic steel at the center and back of the sword.
Source

It can be done in three ways (that I know of):

1. with the application of some kind of a heat-sink, usually clay or refractory cement
2. by partially quenching the blade, where one only dips the very edge into the quenchant
3. by fully hardening the whole blade and then isolating the edge and extremely tempering the spine

I have done the first two, with the first one being my process of choice.

Aside of the different techniques of quenching, there are also different approaches of bringing the hamon out.

There's not really the official or the best one, most of the knifemakers have some kind of a secret and/or prefered recipe.
You can bring the hamon out by polishing with stones, sanding paper, buffing and by applying some kind of an acid.
The traditional one is done by (natural) sanding stones, and most of the purist consider the application of acid a blasphemy. I like my hamon to be really pronounced, so I use strong ferric chloride acid, and let me tell you what I think about tradition.

Tradition is stupidity on purpose

As with most of the cool stuff in steel processing the hamon was introduced in Japan, around 8 century.
The legend being that the inventor was Amakuni.

The idea behind the differential treatment is that by leaving the spine soft, the blade (sword) will become flexible while the edge is kept hard and therefore sharp for a long time.
Since I don't make swords or choppers I mostly do differential treatment for the visual effect - even though it does bring a bit of a dynamic to the blade.

DocSmith Secret Hamon Procedure

I. After I profile the blade I apply the refractory cement in the desired pattern



II. I do, what is commonly referred to as, interrupted quench, where I do a quick dip into a brine, pull it out and then submerge the blade into oil

III. Then I grind the blade and hand sand it to 800 grit, where the hamon starts to pop out ![IMG_20180110_165240_707.jpg]()
IV. I etch the blade in a strong acid V. After the etch I remove the oxides with metal polishing paste

And that's it!

And here's a pic of what it looks like when it's finished

Thanks for stopping by, and if you have any Qs, well you know what to do.

Check out my previous posts on handmade knives:

1. Handmade Knives (custom) 101 #1 – Are You Bipolar?
2. Knives (handmade) 101 #2 – What’s Wrong With My $10 Supermarket Knife?
3. Knives (handmade) 101 #3 What to Think About When Buying a Knife
4. Knives (handmade) 101 #4 Full Custom Build
5. Knives (handmade) 101 #5 If I Spend a Few 100 $ On a Knife Will It Be Sharp Forever
6. Knives (handmade) 101 #6 Design - How to Get the Knife Out of Your Head
7. Knives (handmade) 101 #7 Knife Handle
8. Knives (handmade) 101 #8 How to Spot a Real Deal?
9. Knives (handmade) 101 #9 Making Knives is Not a Clean Hobby
10. Knives (handmade) 101 #10 Little WorkShop of Horrors
11. Knives (handmade) 101 # WIPs April 2018
12. Knives (handmade) 101 #11 You Can Only Get Good By Admitting You've Fu*#$ed UP