Hamon - What is it?

It's that wavy line on the cutting edge of a katana. Traditionally, this wavy effect is achieved by covering the cutting edge with a thin coat of a specialized clay, and the spine with a thick coat of another, then fired to differentially temper the cutting edge, and quenched (rapid cooled) to harden the edge. The cloudy effect is the result of nie crystals forming in the metal which also increases the hardness of the steel.

The spine of the blade is cooled less rapidly due to the thick layer of clay around it and, thus, results in a softer steel. (said to be "shock absorbing"). For all intents and purpose, although it is during the hardening (quenching) process that the martensitic crystalline structure is formed, we'll refer to this overall clay-temper-quench process as "tempering". (Since you can temper (heat) a blade without hardening it, but you cannot harden (quench) a blade without first tempering it).

The important part of this process is the hardening of the razor thin cutting edge of a relatively soft steel sword so that the edge won't roll or dull as quickly during cutting. The white haze that we recognize as hamon is merely a nice visual side effect.

The visible hamon

There is no doubt that a hamon adds to the beauty of a katana. However, it is also often used to mislead and raise the price of an otherwise lower quality sword. A sword is not guaranteed to be better with the presence of a visible hamon nor is it less functional if it does not have a visible hamon. More often than not, a seller uses a fake hamon represented as real to increase the price of a sword.

Modern katanas can be constructed of a through hardened monosteel or a sandwiched steel with a hardened core so that differential tempering is redundant if not undesirable. It is more important to recognize the steel construction of a blade and understand if differential tempering is necessary than to blindly look for a visible hamon.

Additionally, a differentially tempered blade may or may not show a visible hamon depending on how it is polished. The visual appearance of a true hamon has a great deal to do with the level of polish on a sword.

If you have your heart set on a sword with a hamon, you should learn how to distinguish the different types of etched and fake hamon so that you are not mislead into paying more for a blade than what it is worth. (You can still get a sword with a cosmetically applied hamon... you just don't want to pay more for it).

Differentiating a real, fake (cosmetic), and etched hamon

A hamon is considered fake when it is cosmetically applied on a non-differentially tempered blade to increase its visual appeal. This is a little different from a chemically etched hamon applied to a differentially tempered and quenched sword to make the temper line more visible.

True differentially tempered and hardened blades with real visible hamon is not common in production blades, but not all production blades uses fake hamon. Production labor costs increases drastically when we use a real hand clayed temper. You can reasonably expect a true hand clayed, differentially tempered blade to go beyond the $200 to $300 range.

However, nearly ALL fake hamons on Internet auction sites are represented as real hamon. This problem is so rampant because very few people can recognize the difference between a real hamon and a well made fake... many sellers on Internet auction sites do not know if what they are selling are real or fake themselves.

You don't need to frown upon all fake or etched hamon... it does, afterall, make your sword more attractive. Just learn to be able to recognize it for what it is.

So how do you tell the difference?

The best way to learn how to distinguish between a fake and a real hamon (without using a microscope to look for nie crystals) is to get used to comparing real and fake hamons over time. The following are several images of fake and etched hamon for you to reference:

It is quite fun and enjoyable to look at the various tempered and etched hamon. There is an almost limitless variety of both real and etched hamon styles.

Learn to distinguish and appreciate both for what they are. Some people make it a hobby to painstakingly hand etch their project blades using chemicals on q-tips and can create some amazing results.