Any ideas what this is?

[Maff]

Hey folks, hope everyone’s doing great. I’m looking at a line running from the shinogi into the hamon and running a bit within it - hopefully these pics will come out ok. Any advice on what this might be? Thanks!

[George KN]

Is it in the steel, or kind of on it? Its shape makes me think it might have been lying on a cloth or pillow (that may have had grease or something acidic on?).

[Maff]

16 minutes ago, George KN said:

Is it in the steel, or kind of on it? Its shape makes me think it might have been lying on a cloth or pillow (that may have had grease or something acidic on?).

Hi George, yes it’s in the steel. I oiled the blade earlier and it really popped out so to speak

[Robert S]

It does look a bit like a slightly acidic liquid may have gotten on the blade at some time.  Don't think it's a forging (deep) issue.

[Rawa]

Especially if there is no mark of it in shinogi ji part.

[Maff]

9 hours ago, George KN said:

Is it in the steel, or kind of on it? Its shape makes me think it might have been lying on a cloth or pillow (that may have had grease or something acidic on?).

Hi George, yes it’s in the steel. I oiled the blade earlier and it really popped out so to speak

[Maff]

Thanks guys! I’ll try and upload some better photos. Appreciate your time in taking a look