Were Japanese swords tempered?

Phillip Patton

Phillip Patton

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I hear a lot of "bragging" about Jap swords being so tough because they had a soft spine and hard edge. But I remember reading somewhere that they left their edges full hard, not tempered. Is this true? If so, I wonder if the blades might not have been as durable if they had instead been through hardened, and well tempered?

Note, I'm not trying to start an argument here, I want to know from someone who knows better than I, if Japanese swords were tempered.

I'm sure the issue of Japanese vs. European swords has been beaten to death many times, I don't really want to get into that.
 
I have the video with Yoshindo Yoshihara forging a sword, In it, after he quenches he leaves the blade wet, then puts it back in the coals until the water steams off then quenches again. Kind of a temper cycle I guess. With the low carbon core I guess all he is trying to do is prevent cracking in the Higher carbon outer/edge.

Shawn
 
I'm talking about the old swords. I think it was in Yoshiharas book that I read that in the old days they didn't temper. Nowadays they do, because they know better...
 
The swords I have read about were interesting examples in bladesmithing.

They were not made of a mono-steel. The idea they had was to wrap a higher carbon steel around a much lower carbon steel.
The idea behind useing two different steels is that the stronger inner steel would be harder to snap than the harder outer layer.
At some areas in history there were some smiths that were useing several type of steel in different positions along the sides of the sword to reach the goal of a final sword that were hard to snap but would hold a sharp edge.

We also have to keep in mind that all their steel was always a mix that was hand made, sometimes by the smith himself.
Many smiths would have their own systems of turning iron-sand into steel that took many steps to reach.

Then when they were layering on the clay, they also would not just add clay to the spine to slow that cooling, but they would also drag some of the thicker clay down into the cutting edge too.

The reason they had thicker clay down in the cutting edge was to bring that form of steel that is harder to snap down into the cutting edge.

This means that although most of the cutting edge would be that martencite, there also would be a mix of other forms of steel every 1/2" or so.

The resulting cutting edge of the Katana was very hard, but also had within it the ability to stop a crack right away should one form in battle.

As for tempering, I also have read that they would place the katana back into the forge after the quench to get rid of some of the stress.
Many times they would go back and forth from coals to quench tank a few times to get just the correct hardness and strength they were seeking in the final blade.
 
If I may speculate from a position of near complete ignorance, I think they must have been tempering at some point, in some manner.

SOMEONE must have figured ot that the steel is tougher when slightly re-heated, It's alot simpler than figuring out how to forge weld high and low carbon steel. Although, low carbon steel doesn't get hard anyhow, so maybe they relied on it's properties alone to confer the durability to the blade?

Heh, I'd like to know the answer to this one too!
I've often wondered if the superiority of the japanese sword may have had more to do with it's shape, rather than it's metallurgical properties. Anyone ever notice that a katana seems to be so much more fast and agile than the larger and heavier blades used in some other cultures? It's much faster than a longsword or broadsword, and with it's narrow cross-section, must be able to pierce armour at least as good, if not better. The weight of a good katana always feels comfortable in the hand, with that perfect mixture of speed and power.

But someone with the actal data can chime in anytime!
 
The Japanese sword reflects the type of war fighting it was used in.

For a lot of their history the Japanese were only fighting against themselves and had no use for a sword that could go up against metal armor as few had any to wear.

However the design of swords in Japan changed very fast when they were attacked from off-island by guys who did wear thick armor when they found that the normal Katana design was unable to cut their foes.

The swords became more thick and more heavy as time went on.
Some of the early swords were very thin and very light as they were only used against flesh or grass armor.
 
it is thought that in the past, some smiths tempered the edge, others did not. It is a fact that mnay/most smiths did temper the blades made during WWII. Today, smiths usually temper the blades as well.
 
Allan Molstad said:
The swords I have read about were interesting examples in bladesmithing.

They were not made of a mono-steel. The idea they had was to wrap a higher carbon steel around a much lower carbon steel.
The idea behind useing two different steels is that the stronger inner steel would be harder to snap than the harder outer layer.
At some areas in history there were some smiths that were useing several type of steel in different positions along the sides of the sword to reach the goal of a final sword that were hard to snap but would hold a sharp edge.

We also have to keep in mind that all their steel was always a mix that was hand made, sometimes by the smith himself.
Many smiths would have their own systems of turning iron-sand into steel that took many steps to reach.

Then when they were layering on the clay, they also would not just add clay to the spine to slow that cooling, but they would also drag some of the thicker clay down into the cutting edge too.

The reason they had thicker clay down in the cutting edge was to bring that form of steel that is harder to snap down into the cutting edge.

This means that although most of the cutting edge would be that martencite, there also would be a mix of other forms of steel every 1/2" or so.

The resulting cutting edge of the Katana was very hard, but also had within it the ability to stop a crack right away should one form in battle.

As for tempering, I also have read that they would place the katana back into the forge after the quench to get rid of some of the stress.
Many times they would go back and forth from coals to quench tank a few times to get just the correct hardness and strength they were seeking in the final blade.
Click to expand...

I don't mean to nitpick, but when you say "stronger" I think what you mean is "tougher". Hard steel is stronger than soft steel, but soft steel is tougher than hard steel.

I understand the how and why of Japanese swordsmithing pretty well. My question is, did they in fact temper the hardened edge?



If I may speculate from a position of near complete ignorance, I think they must have been tempering at some point, in some manner.

SOMEONE must have figured ot that the steel is tougher when slightly re-heated, It's alot simpler than figuring out how to forge weld high and low carbon steel. Although, low carbon steel doesn't get hard anyhow, so maybe they relied on it's properties alone to confer the durability to the blade?

Heh, I'd like to know the answer to this one too!
I've often wondered if the superiority of the japanese sword may have had more to do with it's shape, rather than it's metallurgical properties. Anyone ever notice that a katana seems to be so much more fast and agile than the larger and heavier blades used in some other cultures? It's much faster than a longsword or broadsword, and with it's narrow cross-section, must be able to pierce armour at least as good, if not better. The weight of a good katana always feels comfortable in the hand, with that perfect mixture of speed and power.

But someone with the actal data can chime in anytime!
Click to expand...


There's plenty of people who would question the superiority of the Japanese sword in the first place. ;)

I think it was in one of Jim Hrisoulas's books that I read about the edge being full hard (not tempered), and prone to chipping.
 
Again, I'm not interested in how they do it now, I want to know whether they tempered their blades 500+ years ago, because those are the blades that have become invincible in many peoples minds...
 
Allan Molstad said:
That may mean that to you, however I use the term in my own different way to reflect how I use the term in my thinking...
Click to expand...

That's not "what it means to me". I'm using the terms that metallurgical science uses to describe these things. I think it's wise use their terms, simply to avoid confusion, and make sure we're all on the same page....
 
One of the reasons we even know about the Japanese katana is the place the sword had in the Japanese world.
There was just a type of magic that people viewed that sword had.
The smiths really did protect the secrets of how each sword was made...
It would be like asking how do we make a Stealth Plane today.
There is much they kept secret and is lost to history because secrets were passed on in person and never writen down.

I do believe that some of the swords made now are far better than anything made in history.
However the image we have of the power of the katana in history is hard to beat.
 
flatgrinder said:
Depends on the smith and specific time in history, as well as different schools and different methods of heat treating.

Here's some info:

http://en.wikipedia.org/wiki/Katana
Click to expand...

I didn't read the whole thing; I skimmed over the section on forging and heat treating, and I didn't see anything about tempering, but that could could just be an oversight. Wikipedia is not infallible...
 
Phillip Patton said:
I didn't read the whole thing; I skimmed over the section on forging and heat treating, and I didn't see anything about tempering, but that could could just be an oversight. Wikipedia is not infallible...
Click to expand...

Yeah, I know. I didn't read the whole thing either, just thought it may be helpful. :)

Usually, Japanese smiths group "heat treating and tempering" into one step (ie. simply "heat treating"), so what I was trying to say was that different schools have different methods. There isn't one way to do things, it's like us, many different knifemakers, making knives in different ways. Some people do a single quench, some triple quench, some double temper, some triple temper, etc. Even the "clay" which is used to coat the blade is made differently in different schools, eg. more charcoal in the mix from one smith to another.

As for tempering, I believe they did. However, the extent by which they did it would vary by school. They tested their swords on convicts and by cutting bamboo, and the Japanese being inquisitive perfectionists, more than likely refined their "recipe" over time. If a sword chipped, believe me, they would have figured out tempering. Plus, Katanas have a reputation for being very sharp, ever try sharpening a fully hardened piece of 1080? It'll chip and have a crappy edge. Now try chopping bamboo with it.

Maybe contact Don Fogg for more info. I know he has studied this for a very long time.

Hope this info helps!
 
Allan Molstad said:
The Japanese sword reflects the type of war fighting it was used in.

For a lot of their history the Japanese were only fighting against themselves and had no use for a sword that could go up against metal armor as few had any to wear.

However the design of swords in Japan changed very fast when they were attacked from off-island by guys who did wear thick armor when they found that the normal Katana design was unable to cut their foes.

The swords became more thick and more heavy as time went on.
Some of the early swords were very thin and very light as they were only used against flesh or grass armor.
Click to expand...

You have this backwards. Samurai swords were thicker to begin with. The period leading to the shogunate was all out fief war at times. During this time all serious armies wore full armor. If you dont believe me go look at the swords and arrows from the fuedal period of japans history. During this time the hevier longer Tachi was preffered to the Katana. The Japanese hadnt worn grass armor since they met the chinese and that was long before samurai swords of any kind.

When the shogun united Japan he knew he only had a chance of control over the daimyo (provincial warlords of the edo period) and that was to seperate them from there fief and the life long rivalries and infighting. He summoned all Samurai to edo to acomplish this.

This is the period of armorless samurai. They became bored and etiquete and duels became the martial part of there life. The code of conduct was so strict that the wrong gesture towards a man with 2 swords would, due to social expectations, lead to a duel. Swords in this time period are what we now think of as sumurai swords. This period of Japanese history has no foriegners. For 300 years the Japanese lived in isolation. It was not until metal warships showed up in there harbor that they had to deal with anyone else at all. At that point the country was forced into the Mejing Restoration period. Samurai and there offspring were forced to cut off the top knots and stop ritual suicide and other facets of samurai life. After this they never fought anyone with swords unless you count the use of Toyama Ryu during WWII and the events leading up to it.

Nakamura sensei cut with several well maintained edo period swords and I can say that they seemed to be tempered. It may be that the quench in clay didnt leave the cutting edge to hard in the first place requiring no temper. Not shure though. I think it deppends mostly on the year and the smith. Flatgrinder is correct about testing blades on people. I have seen a marking indicating that the shinken had chopped through 3 people in a slice. I dont think a fully hardened blade would sever that many bones without chipping.
 
Shakudo said:
You can't harden mild steel or iron unless you consider a rockwell hardness of 30 hard.

info link.

http://www.royalarmouries.org/extsite/view.jsp?sectionId=3003
Click to expand...

The samurai swords of the edo period had nothing to do with mild steel in the sense that thats what they were made of. The iron was extracted from the sand or smelted from viens and carbon was added by the smiths. I have held many swords from the japanese smiths and none are mild steel. All blacksmiths everywhere had to figure out how to forge crappy steel into something workable. Even early japanese learned how to make steel from iron from the chinese. If not they could not make laminates such as the one you link. Also the quality and techniques of smiths varied greatly just as they do today. The best made swords of that era are still around and can be easily examined and even cut with if you so wish. The link you provided points out that this ios just one of many ways used to create such swords and many smiths used alot more steel than that.

taken from your link "This is just one way in which Japanese swordsmiths welded iron and steel together within the blade, but the steel always forms the cutting edge."
 
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