Ripple Effect on Mirror Polished Ji?

[Jnuzzo]

Noob to nihonto, and not fully understanding what causes a ripple effect of a mirror polished ji in certain light?

 

I get that the folding could give you waves, but wouldn’t the polishing take that out? … or does differential hardening remain as a slight topological pattern on the ji post-polish?

 

Sorry if it’s a dumb question, I just don’t want to self-educate incorrectly so I thought I’d ask you guys.  
 

Photos aren’t great but should give you an idea of what I’m talking about.  
 

thx, Jeff

[Shugyosha]

Hi Jeff,

They may be caused by a bent blade having been straightened and are called shinae. 

 

https://www.japaneseswordindex.com/kizu.htm

[Jnuzzo]

6 minutes ago, Shugyosha said:

Hi Jeff,

They may be caused by a bent blade having been straightened and are called shinae. 

 

https://www.japaneseswordindex.com/kizu.htm

That makes perfect sense, thank you!  And thanks for the link.  I’m guessing when it’s on both sides of the blade it could stem from the forging or tempering bend in that axis?

[Jnuzzo]

8 minutes ago, Jnuzzo said:

That makes perfect sense, thank you!  And thanks for the link.  I’m guessing when it’s on both sides of the blade it could stem from the forging or tempering bend in that axis?

Knowing the terminology really helps with knowing what to search for, thx again!

Edited Sunday at 09:47 AM by Jnuzzo

[eternal_newbie]

5 minutes ago, Jnuzzo said:

is a good polisher supposed to grind it out for a flawless topology in any light, or do they intentionally leave tiny nuances of forging in a final finish?

 

For a new blade, generally if it's not small enough to be ground out, the smith wouldn't sign the blade and forward it for polishing (especially given that they're only allowed to produce a limited number of blades each month).

 

For older blades being touched up, it depends on how deep the flaw goes - usually the integrity of the blade is prioritized above a flawless topology, especially if you don't know exactly how much surface metal would need to be ground down to erase the flaw(s).

[Shugyosha]

To be honest Jeff, that's a bit technical for me. The logical bit of my brain would say that you would only get shinae on the side of the blade that has been compressed rather than stretched but that might be wrong as this is a flaw that isn't that common and that I've only ever seen in pictures. I don't recall seeing them on both sides of the blade but that isn't conclusive. 

 

I understand that, if minor, they can be ground out but it is a flaw so again, using what passes for my reasoning, they would be removed if possible - I've just seen Rohan's post which probably sums it up pretty well.

 

Some more information on flaws in this thread and the third post has a picture from an old book which might interest you. 

 

 

[Jnuzzo]

3 minutes ago, eternal_newbie said:

 

For a new blade, generally if it's not small enough to be ground out, the smith wouldn't sign the blade and forward it for polishing (especially given that they're only allowed to produce a limited number of blades each month).

 

For older blades being touched up, it depends on how deep the flaw goes - usually the integrity of the blade is prioritized above a flawless topology, especially if you don't know exactly how much surface metal would need to be ground down to erase it.

This is probably a really dumb question, but curiosity hasn’t killed me yet lol … if a shinae developed during forging, and the pattern of the minuscule creasing all ran mostly perpendicular to the cutting edge and curvature of the blade, what structural instability would that cause during a strike?  i.e. how does that flaw progress into failure of the blade?

[eternal_newbie]

Generally shinae themselves aren't considered a structural integrity problem and are unlikely to develop into a bigger problem on their own - but they do indicate that the blade was abused or faced some serious stress in battle, and thus are a warning sign that internal structural weaknesses may have developed as a result.

 

Think of it as seeing a giant dent in a car's side door; the dent itself likely has no bearing on the roadworthiness of the vehicle, but having received a perpendicular hit like that, you'd want to check that the suspension's not shot.

[eternal_newbie]

There are also some schools where a specific type of shinae - shinae-ware, or small crack-like openings in the horizontal grain - are expected and not considered a flaw at all. In particular, the Hosho school's masame-hada has a tendency to produce these and it's even considered a kantei point for that school.

[Jnuzzo]

14 minutes ago, eternal_newbie said:

Generally shinae themselves aren't considered a structural integrity problem and are unlikely to develop into a bigger problem on their own - but they do indicate that the blade was abused or faced some serious stress in battle, and thus are a warning sign that internal structural weaknesses may have developed as a result.

 

Think of it as seeing a giant dent in a car's side door; the dent itself likely has no bearing on the roadworthiness of the vehicle, but having received a perpendicular hit like that, you'd want to check that the suspension's not shot.

Ah that makes sense.  Is shinae supposed to be able to be blatantly seen with the naked eye or should you have to hunt for it with lighting angles and magnifying lenses etc?  Or just different degrees of it present themselves differently?

[ROKUJURO]

SHINAE are superficial cracks in the steel after a bend on the stretched side of a blade, and of course they are not beneficial to the structural integrity of it.

What we see in Jeff's blade was correctly described as ripples, and they are something quite different. They can develop when the preliminary work in a BOHI left out a stage or two of fine grinding lengthwise which is tedious work. The final polish with a MIGAKI-BO 'compresses' the surface to a very small extent, and using only a pointed MIGAKI-BO can then produce these ripples. With differently dimensioned tools, these can be avoided as you can see on many good swords.

But I will add that some sword construction methods also might provoke the occurrence of these ripples.

I would not consider them negative in technical hindsight at all. 

Looking at this feature with a microscope/high magnification will clear that up easily.

[eternal_newbie]

27 minutes ago, ROKUJURO said:

The final polish with a MIGAKI-BO 'compresses' the surface to a very small extent, and using only a pointed MIGAKI-BO can produce these ripples.

 

Very interesting, thank you for the insight!

[ROKUJURO]

Just for a better understanding I am showing some of my MIGAKI BO. I think they are made from a highly hardenable carbon steel, probably something like ball-bearing or so.
 

[Lewis B]

Always fascinating to see tools used by swordsmiths. I assume a Sen was used, even in ancient times, to shape the blades prior to being passed to the togi-shi. I can certainly see how poor application of this tool could cause such imperfections. 

 

 

From what I can tell from the low Rez images are that some of the 'creases' are convex and others concave. I would say these were the result to reshaping or straightening after sustaining damage. 

[Geraint]

Dear All.

 

To clarify and not to contradict.  Shinae are fine cracks in the blades surface, often appearing together.  However mukade shinae, or giant centipede shinae, are indeed cause by straightening a bent blade, they appear generally at right angles or thereabouts, to the blade edge and sometimes resemble crackled ice.  Rather like a fukure burnishing will not remove these, they are miniature delaminations. According to this link, http://www.ksky.ne.jp/~sumie99/flaws.html they can sometimes be removed by polishing.  You will have to scroll down a little to find this specific fault.

 

As is so often the case applying logic to the terminology used is a waste of effort, just because shinae refers to actual cracks in one case it seems that it does not neccesarily mean cracks in the other.  I cannott see well enough in the pictures of the original blade to be sure but I do suspect that they illustrate mukade shinae.

 

All the best.

 

 

Edited Sunday at 03:01 PM by Geraint

[Natichu]

5 hours ago, eternal_newbie said:

There are also some schools where a specific type of shinae - shinae-ware, or small crack-like openings in the horizontal grain - are expected and not considered a flaw at all. In particular, the Hosho school's masame-hada has a tendency to produce these and it's even considered a kantei point for that school.

My understanding was that shinae and shinae-ware run perpendicular to the blade, whereas the kitae-ware one sees in Hosho run with the masame (as openings in the grain), so parallel to the blade. 

 

Markus Sesko defines as follows:

 

"shinae (しなえ) – Cracks or wrinkles running crosswise through
the ji. Can be caused by poor steel including much of slag or a rough
forging. See also mukade-shinae (百足しなえ)." 

[Jnuzzo]

On subject blade it’s not cracks at all, but the mukade-shinae wrinkles could be a culprit, though I’m having a tough time finding clear photo examples for comparisons.  
 

I’m finding some areas that have a rounded / circular pattern of it as well, and it looks to be somewhat present throughout the Ji on both sides of blade to varying degrees.  
 

It’s hard to clearly see even with a magnifying glass (and my eyesight lol), but I’ll get some better magnification and keep inspecting it / reading about it.  
 

Couple photos of the circular ones just  for the heck of it as well as a non-magnified shot.  

 

 

Edited Sunday at 08:53 PM by Jnuzzo

[ROKUJURO]

Jeff,

now it is clear that the phenomena are not cracks or SHINAE.

I have a question to another feature: Is there a real HAMON? Even in your magnified photos I don't see traces of NIOI or NIE.
What kind of blade is this? Can we see the NAKAGO please (oriented vertically tip-upwards without HABAKI).

So in case this was a machine-made blade, we could suspect the SHINOGI-JI was mirror-polished with a machine which would explain the above pictured phenomena.

[Jnuzzo]

6 hours ago, ROKUJURO said:

Jeff,

now it is clear that the phenomena are not cracks or SHINAE.

I have a question to another feature: Is there a real HAMON? Even in your magnified photos I don't see traces of NIOI or NIE.
What kind of blade is this? Can we see the NAKAGO please (oriented vertically tip-upwards without HABAKI).

So in case this was a machine-made blade, we could suspect the SHINOGI-JI was mirror-polished with a machine which would explain the above pictured phenomena.

It looks like a real and active hamon to me, and looks like a hand polish as the polisher marks are there under habaki.  It’s definitely a hand made blade though.  
 

The light n focus angles I had to use to try to get the shinogi-ji texture might have muddled the hamon a bit.  
 

Looks edo to me, and is an Okimasa gimei.  Large and meaty, with a 29 1/4” nagasa and 1 3/8” width. 
 

I mainly grabbed it because the size was pretty cool and it had a full set of nice Kikuchi Tsunekatsu fittings with interesting properties.  Really pretty mottled lacquer saya as well.  
 

WW2 trophy and pretty clean / well-kept, so I thought it would be a nice piece to learn more on (my others aren’t that great and not in good enough polish to really see the things I want to learn about).  
 

I’ll take some pics when home later tonight.  Thank you for the guidance.  

 

Edited yesterday at 05:13 AM by Jnuzzo

[Jnuzzo]

5 hours ago, ROKUJURO said:

Jeff,

now it is clear that the phenomena are not cracks or SHINAE.

I have a question to another feature: Is there a real HAMON? Even in your magnified photos I don't see traces of NIOI or NIE.
What kind of blade is this? Can we see the NAKAGO please (oriented vertically tip-upwards without HABAKI).

So in case this was a machine-made blade, we could suspect the SHINOGI-JI was mirror-polished with a machine which would explain the above pictured phenomena.

Photos.  I’ll get better at capturing hamon in time lol.  I haven’t learned enough to know what I’m talking about with hamon yet, but it looks at least true to me …

[ROKUJURO]

Hi Jeff,

correct, it is there. The photos are mostly bad, but they show a NIOI-based HAMON. 

[jeremy]

On 2/22/2026 at 8:25 PM, Shugyosha said:

Hi Jeff,

They may be caused by a bent blade having been straightened and are called shinae. 

 

https://www.japaneseswordindex.com/kizu.htm

I agree . Ive used so many swords for tameshigiri in Japan and here in Australia and have bent more swords than id like to think about. Some of the bent and re-straightened swords had exactly this ripple shinae in the shinogi-ji. I think it depends on the severity of the bend too. 

[ROKUJURO]

As explained above, these ripples are not stress cracks, so not SHINAE.