How did the sword pattern come from?

The grain resistance of the sword body is formed by grinding and quenching, and the grain resistance of the sword body urine is formed by adding special chemicals in this process and after a series of treatments.

Specifically, when making the sword body, the swordsman will add some chemicals, such as urine, plant juice, etc., at a specific position, and then heat the sword body to a suitable temperature and quench it, so that these chemicals form different oxide precipitates on the surface of the sword body, thus forming a unique reverse pattern.

It is worth noting that anti-sword urine tattoo is a very old technology. Modern swordsmen usually do not use this method, but use other more reliable methods to build high-quality swords. In addition, because the urine contains some harmful substances, the urine of the sword body is unsanitary, so such treatment is not recommended.