Ignorant question about Katana

[wuyeah]

Hello, Newby's ignorant question of the day is:

The traditional Japanese Katana blade has "wave" patterns that across the blade body in half. Was the pattern a type of damascus effect or that "wave" is actually something else?

 

[Stormdrane]

I think you're referring to the 'hamon' on the blade. It's the wavy line of the tempered edge where the blade is quenched. I'm sure someone will be able to give a much better explanation of the process and origins of it.

 

[Thomas Linton]

I understood that clay is applied to the already-quenched blade before tempering in order to produce the hamon - temper line.

Have you considered www.swordforums.com?

 

[Cougar Allen]

 

[knife saber]

The hamon is created during the quench - it's an artifact of the hardening process, rather than of any post-heat-treat tempering steps. In fact, if I recall correctly, historically, Japanese swords were not always tempered after hardening. The wavy line you see is the boundary zone between different formations of steel caused by the clay altering the rate of cooling in different areas of the blade during the quench.

 

[wuyeah]

Does hamon provide a difference in performance? or it was function pure decorative? Is it hard for knife smith to create and control hamon?

Personally I like hamon, they are nice. Sometimes i feel damascus is too much in decoration and took away the beauty of simplicity. I haven't see hamon on folders, or modern tactic, dagger etc. Is there a reason behind?

 

[knife saber]

Hamon allow for a hard edge and a soft spine. This is critical in sword-length blades because a hard blade would be relatively brittle, and a soft blade wouldn't hold an edge. Everything about the steel in swords is done for a purpose - their aesthetic benefits/drawbacks are, in my opinion, purely coincidental. Western swords dealt with this problem by using spring tempers, which were harder than the softest part of a Japanese sword, but possibly softer than the hardest part of a nihonto. Both are time-tested solutions, and both have beauty, if you ask me.

Swords and knives are different things, so performance in one can be aesthetics in another... Hamon in general are not things that mass-producers can hope to achieve in numbers and at costs conducive to a profit. Hanwei makes a variety of swords and tanto with true hamon, and they are by most accounts high quality items. Also, many blades are made of stainless steels, and I've never seen a stainless blade with a hamon. There are differentially tempered blades, which are different from clay-hardened blades - they don't show a hamon, but have the same properties of a harder edge and a softer back. So the practical benefit is there, but without the aesthetic side-effects. I've heard that differentially tempered blades are tougher than through-hardened pieces, and therefore better suited to situations (like splitting wood, batoning, etc.), but I have no first-hand experience with situations that would confirm or deny that statement.

Long story short, hamons do have a function, but the functionality they represent is perhaps not particularly critical in short blades.

I'd also say that you should examine an old nihonto up close before assuming that they're simple - the folding process Japanese smiths of old used to purify and homogenize their steels led to a very subtle, but very complex pattern within the steel - looking up close, these patterns can be every bit as complex as those in pattern-welded steel, but with a subtlety that defies the casual or uninterested observer.

 

[wuyeah]

Hi Knife Saber, have to say, very impressive information. You open the door now i wish to know more about blade/sword production. Thanks.

Tomorrow is gonna be a library day.

 

[infamous]

In adding on to "knife saber's" response, the "hamon" definately does have a function, and to describe it very simplistic, so it may be easy to comprehend, would be that the hamon is like a line through the middle of the blade, separating the edge which is the harder side, and the spine being the softer side. This is important so that when an object is struck, the harder tempered edge will contact the object and make the cut, whilst the softer spine will flex and absorb the impact. Without tempering the blade in this way, as knife saber mentioned, it would be too brittle, and simply snap on impact, whereas by differentially tempering a blade using clay to produce a hamon, it is possible to make the rear half of the blade softer than the edge, so that the entire blade won't be as brittle, and therefore won't snap, and will last longer, cut more efficiently, and effectively.

So whilst the "hamon" is visually pleasing to the eye, it is definately a functional element, and crucial for that matter, in that every quality, functional katana should be differentially tempered, therefore having a hamon.

In Ancient Japan, the pattern of the hamon could often be used to identify the swordsmith whom created that particular katana, in terms of the number of "ripples", the flow/pattern and so forth. Nowadays, the quality katana's are traiditionally tempered to produce a hamon, however the lower quality katana's are simply acid-etched to bring out a hamon, however if you compare the two, the inferior quality hamon will in no way be as stunning as the traditionally clay-tempered hamon.

 

[Rich S]

Might want to look at this site. Lots of good info and over 2 hundred links to
other Japanese sword sites.

http://www.geocities.com/alchemyst/nihonto.htm

Rich S

 

[knife saber]

Yes, I should have suggested it myself. Dr. Stein's index is probably the best available internet resource for Japanese swords - no weird myths, no outlandish claims, simply a wealth of historical and factual information about Japanese swords and swordsmithing.

The sugata evolution section is always worth a visit or two or three...

 

[hank_rearden]

differential tempering (or differential hardening in the case of japanese swords) is not typical in the sword-warring west. over there, high carbon blades were given a uniform spring temper to make them tougher and survive edge-to-edge clashing. you rarely ever see japanese blades clash (except in the highlander series).

 

[knife saber]

That's not strictly true - if you listen to smiths, you'll find that with European swords, the use of shallow-hardening simple steels and basic heat treating yielded a sword that wasn't differentially hardened in the same way as a Japanese blade, but still had a hardness gradient from edge to spine.

Both European and Japanese swords were capable of surviving edge to edge impacts. Neither would come up completely unscathed.

 

[Will P.]

Knife saber's information is dead on.

Spring tempering is a much more recent process. From a mechanical prespective it can produce superior swords. Just a mech engineering student, not trying to antagonize hamon fanatics! *drops and finds cover*

 

[knife saber]

Hey, a MechE! I'm a fake engineer (BSci.Eng.), but a lot of my friends are MEs.

Hamons are cool, but performance should always be the goal. Then again, smiths nowadays are combining the best of stiff but springy spines and hard but resilient edges.

 

[David Schott]

Many makers such as myself love working with hamons. Typically, you need a carbon steel that has a steep hardening vurve such as 1095, 1085, 1070, etc. Clay is applied to the spine in a pattern, or in many cases, the blade is brought to critical then edge quenched. Some amazing things can be shown in a hamon. Mainly, what you are seeing is the transition line from pearlite along the spine to martinsite on the edge. These two different metal structures polish and etch differently, which allows makers to bring them out using differing finishing methods. Here are a few recent hamon pics from my shop:

 

[senoBDEC]

Spring tempering was never a recent process..... it's been around a LONG time. Certainly almost as long as European swords made of quality steel (imported from India/SE Asia or native, etc) were produced. And yeah, I recall at least a couple extant swords made of wootz, but while neat looking, there seems to be nothing amazingly impressive about its performance especially when quality steel began to become more common (regardless of the hype). Pattern welding and lamination on the other hand (like wootz crucible steel) can enhance performance from less than perfect steel sources.

As to the hamon.... there is a lot of variation... for instance, I just learned about the hitasura hamon type, which has a stiffer spine, but retains a hardened edge (obviously): example: http://www.nihontoantiques.com/fss140.htm