Why Midare Hamon?

[Carlo Giuseppe Tacchini]

having natural selection in mind and considering the varieties of existing hamon styles, I came to the conclusion that it obviously makes no big difference which hamon a blade should have to kill people...

 

Indeed. A sword in not just an Ha.

[Randy McCall]

A while ago we had a similar discussion about statistics of broken blades. If i am not mistaken, it was based on research made by SUISHINSHI MASAHIDE. If memory still serves, very wide 'fancy' HAMON of SHINTO blades had indeed a higher risk of breaking, but as there were no longer occasions to use blades in military actions, weaknesses showed up mainly in TAMESHIGIRI. The problem is that we do not know much about the 'inner' construction of these blades, so that we cannot compare the testing results scientifically with, say, KOTO blades.

It's interesting to see the translator of Masahide's notes mentions that some blades had a wide hamon, and some a narrow, but that Masahide considered such features of relatively minor importance, as a good smith would engineer other features into a blade to render it less likely to fracture or break:

 

"It is true that there are many Saijo Wazamono smiths that made a hade style hamon. Kiyomaru, Kotetsu, Tatara Nagayuki etc..... Koyama Munetsugu should be mentioned as a maker of a very functional choji hamon in Shin-shinto times. (A nioi deki hamon is not as brittle as nie deki) Also, with koto there are a great many famous cutters with a wide hamon. The core steel of the blade has much to do with its ductile properties, thus its durability. A very skilled smith could overcome the brittle nature of a widely tempered nie deki blade by introducing other durability promoting elements into the construction of the blade. Masahide's observations are hard to put into context but none the less, they are enlightening."

http://www.nihontocraft.com/Suishinshi_Masahide.html

[Hoshi]

Now if we start introducing more variables... 

 

Skin to core steel ratio in cross-section is interesting. A lot of soft core steel would offset the brittleness of a wider hamon. I think I read in one of Darcy's post that the RAI school has very little skin steel compared to its Yamashiro predecessor. Possibly giving their blades both an economic edge in terms of production cost and a reduced risk of breaking. I can imagine that core steel showing up after a few chip repair wouldn't cause screech of horrors in the samourai of old as it does to the modern collector as long as the blade remained with a viable hamon thickness.   

 

Then there is of course the hardness of the core steel and skin steel itself and the hardness of the hamon quenching process. I read somewhere that Koto Bizen used a relatively soft steel that had the good ductile properties even for the skin, compared to centrally-produced/imported shinto steel which was much harder. From there we can assume that for the same hamon thickness and irregularity, the shinto blade was far more brittle compared to the koto bizen sword.

 

I think when the Soshu tradition emerged they didn't have access to the quality raw materials of bizen and hence had to adapt their style out of necessity due to the new iron deposits they were using. It just didn't work and hence they had to change the formula towards thicker swords to survive the more intense quench resulting in harder hamons that would chip more easily. How their steel differed from the yamashiro and Bizen deposits I'd like to know. I'm also curious if the nie-deki was a necessity to make this steel work or just the byproduct of their experimentation as they tried to adapt to the new deposits. 

[PNSSHOGUN]

Again I bring up the Koa Isshin Mantetsu swords. They were designed via thorough research and testing of all periods of blades to ascertain what was the optimal and most effective construction for the Japanese sword in combat.

 

Very hard edge of 70+ rockwell, like the koto masters, suguha hamon, scientifically designed construction of softer rod inserted into hard shingane pipe for precise distribution of core and outer steel.

[ROKUJURO]

John,

is there any evidence of the hardness you mention? Carbon steel goes normally up to max. HRc 66 if it has about 1.5% of C. 

[PNSSHOGUN]

The info is from ohmura study, here's the full link. I thought it was quite interesting how hard those Koto masters swords were. I'm assuming this table is in Rockwells but no actual system was noted.

 

http://ohmura-study.net/998.html

[ROKUJURO]

John,

I have looked that up to be sure. The 'normal' hardness scale of Rockwell C ends at 68 for low alloy carbon steel. OMURA's data are not Vickers or Brinell either, so I have my doubts about his figures. My knowledge is that a hardness (Rockwell C) of 60 to 62 in the edge of a blade combined with a body hardness (measured at the MUNE) of 48 to 52 was measured in KOTO as well as in later blades. OMURA's text suffers a lot from translation problems, so I don't know for sure in some parts what his sources were and what he meant to express.   

[Dave R]

John,

 

I have looked that up to be sure. The 'normal' hardness scale of Rockwell C ends at 68 for low alloy carbon steel. OMURA's data are not Vickers or Brinell either, so I have my doubts about his figures. My knowledge is that a hardness (Rockwell C) of 60 to 62 in the edge of a blade combined with a body hardness (measured at the MUNE) of 48 to 52 was measured in KOTO as well as in later blades. OMURA's text suffers a lot from translation problems, so I don't know for sure in some parts what his sources were and what he meant to express.   

 Koa-Isshin are not low alloy carbon steel.......

[Carlo Giuseppe Tacchini]

 Koa-Isshin are not low alloy carbon steel.......

 

But Koto ones should be.So what used ohmura as scale ?   

[PNSSHOGUN]

I'm thinking it could be a unique system used by Dr. Tawara for swords.

[Carlo Giuseppe Tacchini]

So not academically accepted...

[ROKUJURO]

 Koa-Isshin are not low alloy carbon steel.......

Dave,

 

I think they are, following the data from OMURA:

 

          The chemical components of a Kōa-Issin sword

 

                    Carbon     Manganese     Silicon          Phosphorus        Sulphur 　

Skin steel      0.57            0.05               0.17                0.018              0.003 　

Core steel     0.23            0.15               0.21                0.020              0.008

 

In his article he mentions even the absence of titanium, so this steel seems to be quite 'pure' which corresponds to low-alloy. High-alloy steel with considerable amounts of alloying components to enhance the properties would not allow quenching in water.

 

The meaning of low-alloy carbon steel can be found here: http://www.totalmateria.com/articles/Art62.htm

 

[PNSSHOGUN]

So not academically accepted...

Probably not. I wouldn't throw the baby out with the bathwater on it though. 

[seattle1]

Hello All: 

 This has been a very interesting thread indeed, branching and swirling as it has, however the underlying rationale for it was the issue of the robustness of midare hamon. On July 24 above I suggested that useful inference might be drawn on the vulnerability of midare hamon from the decline in the Ichimonji group after the Mongol invasions of 1274 and 1281. More recently Darcy, whose contributions are always interesting, informative and often innovating wrote: "The Ichimonji smiths did not fall because of the Mongol invasions."

 My suggestion had been that the issue has been addressed in an interesting way by Saulius V. Ploplys, in the Mar. - April, 2017 issue of the Newsletter of the JSS/US, pp.6-22. The data presented is longitudinal data, not experimental data, related to smith numbers present in certain schools both before and after the invasions. The decline of the Ichimonji was not dramatic, it was not by edict, it was, according to Ploplys, the usual story of product change as we have know it through history, namely the maladaptation of one product in the face of a superior product for the use at hand. Needless to say the process, or at least partial substitution, took decades, and of course midare hamon have always been with us. It is an interesting aside to note that the strongest resurgence of midare hamon occurred during late Early Edo years through the Shinto era when the likelihood of actual sword use in practice was at an historical low. The less wide and less varied hamon patterns of the Osafune and Kosori groups after the Mogul threats was not a fashion change, it was beneficial adaptation.

 There can be other inferences that could be pointed to as contributory, but in my opinion Saul's contribution is a major step forward in our understanding.

 Arnold F.

[Dave R]

Suddenly realised my post was not really relevant to this thread.