Please help me better understand nie/nioi deki

[JH Lee]

I have a gendai katana that is currently in the process of being restored.  The polisher sent me this in-progress photo earlier today.  Initially, I was extremely disappointed because I thought the hamon was running off of the edge, which would constitute a fatal flaw.  Then again, the polisher informed me that there is nie/nioi in that area and that it was fine.  So, I started to look into nie/nioi deki hamon and its structural properties... which basically tells me that what I am seeing in this photo is probably not a fatal flaw after all.  Could someone with more knowledge and experience help me to better understand how I should interpret what I am seeing?  Thank you!

[ROKUJURO]

John,

I think the (hopefully Japanese?) polisher should be able to make better photos so you could see what is to see.

[Ken-Hawaii]

As Jean says, you need better photos. Ask him to show the nioiguchi, which should quickly indicate if the hamon has really run off the edge.

[Rivkin]

Conventional way: do you see dots in hamon which sparkle if you apply light from the edge's side. If yes, its nie.

Unconventional way: look at the blade straight down while applying light from a side (not from the edge, but from either nakago or kissaki's direction). If you see bright, well distinguished hamon, its in nie. If its sort of hazy,  its nioi. This method helps a lot when you buy swords based on scanned photographs. If its hazy, its not bad, its just a nioi blade. There are exceptions but they are rare.

 

[JH Lee]

Some more photos from the togi, who admits to not being too good at taking photos (and who I don't want to bother too much by pestering for more/better photos).  I have been told that the white misty appearance is not hadori but just the natural hardened steel.  Is the misty part nioi?  Is it softer than the darker parts of the hamon?  Is it functioning as a kind of massive/irregular ashi?  So many questions!!  

 

Thanks in advance for the enlightenment.

[JH Lee]

I know the pictures aren't great, but I would be grateful for your helpful thoughts/opinions.

[b.hennick]

Nie large crystals, nioi small crystals  Smaller word bigger crystals larger word smaller crystals. 

Think of it this way, granulated dsugar crystals vs icing sugar nie vs nioi. 

Individual nei crystals can be seen easily, nioi cannot - - >  misty

[JH Lee]

Thank you, Barry.  Are parts of the hamon that are nioi-deki softer/harder than nie-deki?  No difference?

[b.hennick]

Every blade had nioi, nei is specially created by the smith. I think that there are many things that determine hardness. You should know that the harder the blade the easier it is to chip. That is it is more brittle.

[JH Lee]

Thank you for being patient with me, Barry.  I am still learning. 

 

So, in the images posted above, where the hamon seems to be primarily nioi....  Are those the spots where the blade is potentially more likely to bend/take a set?  Or am I over (or under) thinking it?

[Jacques]

Worth reading :

 

https://markussesko.com/2015/05/29/kantei-3-hamon-boshi-1 

 

 

 

[16k]

On 2/2/2021 at 8:16 AM, JH Lee said:

Thank you for being patient with me, Barry.  I am still learning. 

 

So, in the images posted above, where the hamon seems to be primarily nioi....  Are those the spots where the blade is potentially more likely to bend/take a set?  Or am I over (or under) thinking it?

Actually, the nioi/ nie line is the transitional area where the hardened steel meet the less hard steel. So ashi relieve stress on the blade and supposedly makes them less brittle in those areas

[JH Lee]

1 hour ago, 16k said:

Actually, the nioi/ nie line is the transitional area where the hardened steel meet the less hard steel. So ashi relieve stress on the blade and supposedly makes them less brittle in those areas

 

Right.  But you see in the pictures I posted, what looks to be ashi has become almost a wider "zone" of nioi.  So, less brittle and softer shock absorbers of sorts; which is really cool engineering.  I was wondering what the trade-off would be.  For example, more prone to bending at those places or less able to hold an edge?

[16k]

I would think the trade off to be minimal. Ashi were mainly used to avoid the blade to crack during yakiire. I think a swordsmith (there are some on this board) would be better able to answer your questions. Besides, sharpness is a relative thing, a blade with more niku would be less sharp that a blade with no niku, yet better suited against an armor while a very sharp, no niku blade would probably develop more hakobore or even break in the same circumstance. Envision the whole process as different means to different ends.