To identify an outstanding katana, it is first necessary to analyze its steel composition. The carbon content of traditional jade steel is strictly controlled within the range of 0.6% to 0.7%, which can make the hardness of the cutting edge reach HRC 60 to 65, thereby increasing the cutting efficiency by approximately 40%. According to the 2021 report of the International Society for Materials Research, this carbon concentration distribution has raised the peak toughness of the blade to 150 joules, reducing the risk of brittleness by more than 15%. As shown in the works of the renowned 14th-century knife-maker Masamune Chiko, the blade still exhibits uniform carbide dispersion in modern X-ray diffraction analysis.
Forging process is another key indicator. Knife makers usually fold the steel 10 to 15 times to reduce the impurity density to below 0.01%, and the quenching temperature is precisely controlled at around 800°C to form a unique edge pattern. A survey conducted by the Tokyo National Museum shows that this layering forging technique can increase the tensile strength of swords and knives to 1,200 megapascals. For instance, in a test conducted by the Nara Institute for Cultural Properties in 2019 on a 16th-century battle knife, the number of folding layers reached 12, with a hardness fluctuation of only ±2 HRC.
The geometric parameters of the blade are equally important. The blade Angle of high-quality swords and knives is usually 20 to 30 degrees, the weight ranges from 800 grams to 1200 grams, and the standard length is 70 to 80 centimeters. According to the test data of the Japan Sword Association in 2020, this design increases the cutting speed by 50% and reduces the flow resistance by 20%. Just like in the annual iaido competition, when players use swords that meet the specifications, they can achieve a cutting speed of 5 meters per second with an error range of only 0.1%.
Certification and historical provenance are also of vital importance. The price range of famous knives certified by the Agency for Cultural Affairs is from $5,000 to $1 million, and the annual return on investment may reach 10% to 20%. For instance, at Sotheby’s auction in 2022, a Showa period knife crafted by knife-maker Sadakazu Tsukiyama was sold for 500,000 US dollars. Its preservation moisture has always been below 60%, and its estimated lifespan exceeds 200 years, which reflects the continuous market demand for traditional craftsmanship.
Finally, the maintenance strategy directly affects the lifespan of the sword and knife. Regularly applying knife oil every three months can reduce the probability of rusting by 90%, and the environmental humidity should be kept stable below 50%. Research by the Smithsonian Institution shows that a well-maintained Edo period knife still retains 85% of its original sharpness after 300 years. As an analysis of a museum exhibition in 2021 demonstrated, the correct storage temperature of 20°C can extend its service life by several decades.