Katana Obsidian Wave Oroshigane Kobuse Blade Kuronami Koshirae 黑浪

Folded Oroshigane Steel Shinken (真剣) | Obsidian Wave Katana: TangGu (湯谷) Oroshigane (卸し金) Kobuse Blade (甲伏造) + TangGu (湯谷) Kuronami Koshirae (黒波拵)

This uchigatana (打刀) has a blade forged from in-house refined Oroshigane (卸し金) steel in Kobuse-zukuri (甲伏造) construction, with a hardened outer steel shell around a softer core — the same method used in tamahagane blades to achieve both strength and resilience. Traditional folding produces a mixed Mokume-hada and Masame-hada (杢目肌・柾目肌交じり) grain, while polishing reveals a gently undulating notare hamon (湾れ刃文) created through clay tempering (覆土焼入れ). The saya (鞘) is finished in black raden-style lacquer (螺鈿塗) with luminous reflective particles. Kojiri, koiguchi, and kurigata are made of buffalo horn. A green silk sageo (下緒) is tightly woven. The tsuka (柄) is wrapped in green silk ito over aged yellow samegawa (鮫皮), reinforced with hishigami (菱紙). The menuki (目貫) depict sword dragons (剣龍) in blackened white copper. The fuchi and kashira (縁頭) are white copper with engraved wave (海浪) motifs, finished with blackened patina. The tsuba (鍔) is a round brass guard hand-carved with a wave (海浪) design using katakiribori technique, and finished with blackened patina (煮黒仕上げ).

TangGu (湯谷) Oroshigane Kobuse Blade

This blade is hand-forged (Tezukuri / 手作り) from in-house refined Oroshigane (卸し金) steel, smelted from satetsu (砂鉄) and repeatedly folded (orikaeshi-tanren / 折り返し鍛錬). Forged in Kobuse-zukuri (甲伏造) construction, this Oroshigane shares the same forging lineage as traditional Tamahagane (玉鋼), achieving comparable performance and structure while allowing the smith to refine the steel’s properties by hand.

Blade Forging Details

• Blade Name: TangGu Folded Oroshigane Kobuse Blade (甲伏造)
  

• Forging Method: This blade is forged in Kobuse-zukuri（甲伏造）style, with a hardened outer layer over a softer iron core. It is differentially hardened using clay tempering（覆土焼入れ）, producing a sharp edge, resilient spine, and a visible hamon（刃文).

• Materials: Oroshigane (卸し金) steel smelted from satetsu (砂鉄), refined in-house using traditional methods（伝統的手法による自家製鋼材）

• Purpose: Designed for Iaido (non-sharpened), Kenjutsu, and Tameshigiri (test cutting) practice, as well as for collection, display, and appreciation by enthusiasts and connoisseurs.

Blade Specifications

• Blade Length (Nagasa刃長): Approx 71 cm
• Tang Length (Nakago 茎長): Approx. 24 cm
• Width at Base (Motohaba 元幅): Approx. 31 mm
• Thickness at Base (Motokasane 元重): Approx. 6 mm
• Width at Tip (Sakihaba 先幅): Approx. 22 mm
• Thickness at Tip (Sakikasane先重): Approx. 4 mm
• Kissaki Length (Tip 切先長): Approx. 37 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): Mokume-hada mixed with Masame-hada（杢目肌・柾目肌交じり）— a composite pattern showing wood-grain swirls with straight grain elements, created through repeated folding and layering.
• Temper Line (Hamon 刃文): Curved Notare (湾れ刃文) — a gently undulating wave-like temper line formed through clay tempering (覆土焼入れ).

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 is forged from in-house refined Oroshigane (卸し金) steel using Kobuse (甲伏) construction — a hard outer steel shell around a softer core. Traditional folding produces a mixed Mokume-hada and Masame-hada (杢目肌・柾目肌交じり) grain, while polishing reveals a curved Notare Hamon (湾れ刃文) formed through clay tempering (覆土焼入れ), along with a clearly defined ridge line (Hōmi / 峰).

Fittings and Mountings

Blade Fittings

• Tsuba (Handguard 鍔): Round brass tsuba, hand-carved with wave (海浪) motif using katakiribori technique, finished with blackened patina (煮黒仕上げ).
• Fuchi-Kashira (縁頭): White copper fittings with engraved wave (海浪) motifs, finished with blackened patina.
• Menuki (目貫): White copper menuki depicting sword dragons (剣龍), finished with blackened patina.
• Habaki (鎺): Hand-forged brass with an aged finish.
• Samegawa (Ray Skin 柄鮫): Genuine ray skin aged to a soft yellow hue.
• Handle Wrapping (Tsuka-maki 柄巻): Green silk ito, tightly wrapped with hishigami support.

Saya and Accessories

• Saya (Scabbard 鞘): Traditional-style design reinforced with water buffalo horn at the koiguchi (mouth), kojiri (end), and kurigata (cord knob).
• Saya Lacquer (鞘塗): Raden-style lacquer (螺鈿塗), glossy black surface with subtle reflective particles.
• Sageo (Cord 下緒): Green silk sageo, woven in traditional style.

Measurements

• Blade Weight: Approx. 0.65 kg
• Sword Weight (without Saya): Approx. 1.0 kg
• Total Weight: Approx. 1.35 kg
• Overall Length: Approx. 100 mm