Katana Koi Stone Maru Blade Suiboku Koshirae 锦石

Clay Tempered Chōji Hamon Shinken (真剣) | Koi Stone Katana: TangGu (湯谷) Maru Blade (丸造)+ TangGu (湯谷) Suiboku Koshirae (水墨拵)

This katana is forged in Maru-zukuri (丸造) construction from hand-forged high-carbon steel (高炭素鋼). The edge displays a distinctive chōji (丁子) hamon formed through clay tempering (覆土焼入れ / Fukutsuchi Yakiire). The blade is made in shinogi-zukuri (鎬造) geometry with an iori-mune (庵棟) spine and a chū-kissaki (中切先, medium-sized tip). The koshirae (拵) features a round steel tsuba (丸形鍔) carved with a motif of swimming carp (錦鯉図), finished with a black patina (煮黒 / Nuriguro). The fuchi and kashira (縁頭) are also steel with black patina, decorated with matching carp designs to complement the guard. The tsuka (柄) is wrapped in brown cotton ito (茶色木綿柄糸) with hishigami (菱紙) over natural samegawa (本鮫皮) ray skin, forming a precise hishi-gumi (菱組) diamond pattern. The saya (鞘) is finished in brown ishime lacquer (茶石目塗), giving it a textured, stone-like appearance. The koiguchi (鞘口), kojiri (鞘尻), and kurigata (栗形) are reinforced with water buffalo horn (牛角). A brown cotton sageo (茶色木綿下緒) is tightly woven and tied to the kurigata, completing the dignified mounting.

TangGu (湯谷) Maru Blade

This blade is hand-forged (Tezukuri / 手作り) from high-carbon modern steel (高炭素現代鋼) in a monosteel construction called Maru-zukuri (丸造).

Blade Forging Details

• Blade Name: TangGu Traditionally Forged Maru Blade (丸造)
• Forging Method: This blade is forged in the Maru-zukuri (丸造) style from a single piece of modern high-carbon steel. It is clay-tempered (yaki-ire / 焼入れ) to produce a hardened edge with a visible hamon (刃文).
• Materials: Modern high-carbon steel (kōtanso gendai-kō / 高炭素現代鋼)
• Purpose: Designed for Iaido (non-sharpened), Kenjutsu, and Tameshigiri (test cutting) practice

Blade Specifications

• Blade Length (Nagasa刃長): Approx 73 cm
• Tang Length (Nakago 茎長): Approx. 26 cm
• Width at Base (Motohaba 元幅): Approx. 32 mm
• Thickness at Base (Motokasane 元重): Approx. 6 mm
• Width at Tip (Sakihaba 先幅): Approx. 24 mm
• Thickness at Tip (Sakikasane先重): Approx. 4 mm
• Kissaki Length (Tip 切先長): Approx. 36 mm
• Mekugi-ana (Peg Hole 目釘穴): 1

Blade Characteristics

• Shape: Shinogi-zukuri (ridged blade 鎬造), Iori-mune (flat ridged spine 庵棟), Chū-kissaki (Medium-sized tip 中切先)
• Forging Pattern (Hada 鍛肌): None (Modern monosteel; no visible hada)
• Temper Line (Hamon 刃文): Clay-tempered chōji-style (丁子刃文) hamon – The blade is differentially hardened (yaki-ire / 焼入れ) through clay tempering (覆土焼入れ) to create a functional and distinctive temper line.

Special Features and Workmanship

Hi (Groove) Engraving

• Type: Hi-Nashi (樋なし)
• Processing Range: None (No bohi) – Solid blade for added weight and strength

Polishing Work

• TangGu Polishing Levels:
  • Highest-grade shaping polish 最上・成形研磨 
  • Superior rough polish 最上・下研ぎ 
  • Detailed final polish 最上・仕上げ研ぎ 
• Key Features:
  • The blade features a chōji-style hamon (丁子刃文) formed through clay tempering (覆土焼入れ / Fukutsuchi Yakiire). The shinogi (鋒身筋) ridge is mirror polished.

Fittings and Mountings

Blade Fittings

• Tsuba (Handguard 鍔): Maru-gata (丸形) tsuba made of steel (鋼), finished with black patina (煮黒 / Nuriguro). The surface is carved with a swimming carp motif (錦鯉図) among flowing waves.
• Fuchi-Kashira (縁頭): Steel (鋼) with black patina (煮黒 / Nuriguro), carved with carp designs matching the tsuba.
• Menuki (目貫): Set of menuki placed beneath the brown tsuka-ito (柄糸).
• Habaki (鎺): Shakudō（赤銅 / purple copper）habaki, polished.
• Samegawa (Ray Skin 柄鮫): Natural unbleached ray skin（本鮫皮）under the wrap.
• Handle Wrapping (Tsuka-maki 柄巻): Brown cotton ito wrapped with hishigami (菱紙) in a precise diamond pattern.

Saya and Accessories

• Saya (Scabbard 鞘): Traditional-style saya (拵風鞘), reinforced with water buffalo horn at the koiguchi (mouth), kojiri (end), and kurigata (cord knob).
• Saya Lacquer (鞘塗): Brown ishime lacquer (茶石目塗), creating a textured, stone-like matte finish.
• Sageo (Cord 下緒): Brown cotton sageo, tied in traditional style.

Measurements

• Blade Weight: Approx. 0.7 kg
• Sword Weight (without Saya): Approx. 1.0 kg
• Total Weight: Approx. 1.2 kg
• Overall Length: Approx. 103 mm