White kizu on Koto blade?

[Lewis B]

I've heard these white kizu pits and along the forging folds are due to the smith overheating the blade during yaki-ire. But I think its more likely to be over use of uchiko which becomes embedded in kitae-ware and rust spots. Anyone shed any more light on these unattractive features?

 

 

 

[Tcat]

Shed light is an interesting turn of phrase, because features which appear white in photographs can be caused by reflections along high points, or appear as artifacts of scattered light. Uchiko can be the culprit, but over use is not necessarily the case when normal use will cause small openings to fill with powder also. User error here would be failure to correctly remove the uchiko after it is applied. A good clean with isopropol alcohol and a microfibre cloth would remove any uchiko, were that to be the cause.

 

The examples in these photos seem to be kitae-ware and a small rust pit, or perhaps what was once a tiny fukure now opened by the most recent polish. In the case of the kitae-ware, it looks like light reflecting off the walls of the canyon or ridgeline. Where the other flaw is concerned, it looks to be the same basic cause, light reflecting off the inner surfaces.

[ROKUJURO]

On 5/23/2026 at 9:56 PM, Lewis B said:

.....kizu pits and along the forging folds are due to the smith overheating the blade during yaki-ire....

Hi Lewis,

it is just the opposite. The long KITAE WARE are incomplete welding spots, mostly caused by insufficient temperature in the folding/fire-welding stages. They are often seen on the MUNE as results of the composite construction