What is Aranie in Japanese Katana terminology?

The term "Aranie" (荒沸) refers to a specific pattern that can be observed on the blade of a Japanese sword. This pattern is created during the process of quenching, where the temperature of the blade is rapidly reduced. This sudden change in temperature causes the composition of the iron to form into particles. Among these particles, those that are large enough to be seen with the naked eye are particularly referred to as "Aranie". These particles are scattered in a way that resembles sand, hence the name "Aranie", which can be translated as "rough boiling" or "coarse boiling".

When these particles are concentrated in certain areas of the blade, it creates a distinct pattern that is often referred to as ""Nanako-nie"" (数の子沸), which can be translated as ""roe boiling"". This term is derived from the visual resemblance of this pattern to fish roe.

This pattern is one of the many unique characteristics that can be observed on the blade of a Japanese sword, and it is often used as a criterion for evaluating the quality and craftsmanship of the sword.