Traditionally forged Japanese blades are the best in the world. And honyaki blades forged of pure carbon steel are the crème de la crème. It takes a master craftsman to successfully fashion a honyaki blade. Anyone with a mind to purchase such a knife is likely a fanatic due to profession or passion and will take interest in the sub-categories of this elite class of blades, including shiro-ko or ao-ko, white or blue steel, and abura-yaki and mizu-yaki, quenching by oil or water.
Nearly 40 years ago, with a mind to make mizu-honyaki, water quenched pure carbon steel blades, Mukō began purchasing his own materials and took every spare moment to practice. But blade after blade, after hours of shaping and pounding, would break as the hot metal hit cool water. Though he had been successfully quenching blades in oil, the rapid cooling that water afforded, the very condition that creates the coveted strong edge of a mizu-yaki blade, caused them to crack time after time.
Mukō can point to the exact day his luck changed, the day a man named Okishiba, a deity-like master blade smith, briefly rented space at Kobayashi Hamonten. Mukō patiently awaited an opportunity to observe him at work. He was finally granted entry, but says, “He wouldn’t teach me anything! I could watch, but he wouldn’t teach me anything.” However the chance to observe proved pivotal to Mukō’s success.
Fashioning a fine blade is the pursuit of hardness as it pertains to strength and flexibility. Increase hardness and though a blade has greater potential for retaining extreme sharpness, flexibility is sacrificed and it becomes brittle. The ideal blade is flexible at the spine but hard at the cutting edge. Ultimately hardness is the result of quenching and tempering.
Mukō observed Okishiba coating the knife with a stone and clay wash. Acting as insulation, this coating was the key to successful quenching without fracturing the blade. But Okishiba’s lips were sealed when it came to any details on the recipe or application. Mukō would have to figure that out on his own.
Proving that he long ago had, with brush in hand Muko begins painting a stone gray, soupy glaze flecked with grit onto the gyuto blade. Once quenched in water, the edge cools faster than the core and the blade is differentially hardened. While the edge is rendered extremely hard, the spine remains flexible. Demonstrating that he had also learned the lesson of secrecy, he politely clips any further line of questioning regarding the final annealing stage remarking, “I’d rather not say too much.” Like Mukō all those years ago, we could observe but not inquire.
After another interval in the forge, Mukō’s sends the glowing blade immediately into a basin of water. With a sharp hiss a plume of steam is born. In the blink of an eye, the task that Mukō had spent years perfecting is accomplished with hardly any indication of its difficulty. Pulling the blade from the water, it continues to bleed steam. After one more turn in the forge, Mukō’s work is done.