page_title: Hamon (swordsmithing)
hierarchical_section_title: Hamon (swordsmithing)
caption_attribution_description: English: A katana of the kobuse type, made in the traditional Japanese style. The hardened edge is separated from the softer back by a bright, wavy line, called the nioi. The edge of this bright line, called the hamon, marks the boundary between the martensitic portion (the yakiba) from pearlitic center area (the hira). The wavy shape of the hamon is from the manner in which the insulating clay was appllied before quenching. The inset shows a close-up of the nioi, which is made up of niye. The niye are single, bright grains of martensite surrounded by pearlite, which are seen as the speckled zone between the bright yakiba and the darker hira. The wood-grain appearance comes from alternating layers of steel that have different hardenability.
context_page_description: In swordsmithing, hamon is a visual effect created on the blade by the hardening process. The hamon is the outline of the hardened zone which contains the cutting edge. Blades made in this manner are known as differentially hardened, with a harder cutting edge than spine. This difference in hardness results from clay being applied on the blade prior to the cooling process. Less or no clay allows the edge to cool faster, making it harder but more brittle, while more clay allows the center and spine to cool slower, thus retaining its resilience.
  The hamon outlines the transition between the region of harder martensitic steel at the blade's edge and the softer pearlitic steel at the center and back of the sword. This difference in hardness is the objective of the process; the appearance is purely a side effect. However, the aesthetic qualities of the hamon are quite valuable—not only as proof of the differential-hardening treatment but also in its artistic value—and the patterns can be quite complex.
context_section_description: In swordsmithing, hamon (刃文, hamon) (from Japanese, literally "blade pattern") is a visual effect created on the blade by the hardening process. The hamon is the outline of the hardened zone (yakiba) which contains the cutting edge (ha). Blades made in this manner are known as differentially hardened, with a harder cutting edge than spine (mune) (for example: spine 40 HRC vs edge 58 HRC). This difference in hardness results from clay being applied on the blade (tsuchioki) prior to the cooling process (quenching). Less or no clay allows the edge to cool faster, making it harder but more brittle, while more clay allows the center (hira) and spine to cool slower, thus retaining its resilience.
  The hamon outlines the transition between the region of harder martensitic steel at the blade's edge and the softer pearlitic steel at the center and back of the sword. This difference in hardness is the objective of the process; the appearance is purely a side effect. However, the aesthetic qualities of the hamon are quite valuable—not only as proof of the differential-hardening treatment but also in its artistic value—and the patterns can be quite complex.
  Many modern reproductions do not have natural hamon because they are thoroughly hardened monosteel; the appearance of a hamon is reproduced via various processes such as acid etching, sandblasting, or more crude ones such as wire brushing. Some modern reproductions with natural hamons are also subjected to acid etching to enhance their hamons' prominence. A true hamon can be easily discerned by the presence of a "nioi," which is a bright, speckled line a few millimeters wide, following the length of the hamon. The nioi is typically best viewed at long angles, and cannot be faked with etching or other methods. When viewed through a magnifying lens, the nioi appears as a sparkly line, being made up of many bright martensite grains, which are surrounded by darker, softer pearlite.
caption: Katana shown at a long angle to reveal the nioi. Inset: Close-up of the hamon, showing the nioi as the speckled area between the bright yakiba and the darker hira. The speckles are niye, or individual martensite grains surrounded by pearlite, providing a very tough boundary between the harder and softer metals. (A few larger, isolated niye are visible away from the hamon as well.)
exif: {"Image ImageDescription": "", "Image Make": "Canon", "Image Model": "Canon PowerShot S95", "Image DateTime": "2011:05:03 03:31:39", "Image YCbCrPositioning": "Co-sited", "Image Tag 0x1001": "3648", "Image Tag 0x1002": "2736", "Image ExifOffset": "268", "Image SensitivityType": "Standard Output Sensitivity and Recommended Exposure Index", "Image CustomRendered": "Normal", "Image ExposureMode": "Auto Exposure", "Image WhiteBalance": "Auto", "Image DigitalZoomRatio": "1", "Image SceneCaptureType": "Standard", "EXIF ExposureTime": "1/80", "EXIF FNumber": "4", "EXIF ISOSpeedRatings": "80", "EXIF ExifVersion": "0230", "EXIF DateTimeOriginal": "2011:05:03 03:31:39", "EXIF DateTimeDigitized": "2011:05:03 03:31:39", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "3", "EXIF ShutterSpeedValue": "101/16", "EXIF ApertureValue": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "2", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, auto mode", "EXIF FocalLength": "6", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "3648", "EXIF ExifImageLength": "2736", "EXIF FocalPlaneXResolution": "912000/73", "EXIF FocalPlaneYResolution": "912000/73", "EXIF FocalPlaneResolutionUnit": "2", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera"}