• Sub-Zero Processing and Shiroyama Cutlery's Craftsmanship

  • KIREAJI’s Sub-Zero processing technology rapidly cools steel to below-zero temperatures, significantly enhancing the hardness and durability of the knives. This process, rooted in the craftsmanship and expertise of skilled artisans, results in knives with superior sharpness and lasting performance.

What is Sub-Zero Processing?

  • Typically, knife hardening involves heating the metal to high temperatures and then cooling it to increase its hardness. However, this method does not always achieve uniform hardening.

  • To overcome this, we employ advanced Sub-Zero processing. This technique involves cooling the steel to temperatures below 0°C using liquid nitrogen, ensuring that any unevenly hardened areas become uniformly hardened. Sub-Zero processing ensures consistent hardness throughout the knife, leading to exceptional durability.

  • The Science Behind Sub-Zero Processing

  • Here's a more technical explanation:

  • The quenching process rapidly cools austenite, transforming it into martensite. Martensite is structurally stable and dense, which results in high material hardness. However, not all of the austenite transforms into martensite in a typical quenching process. This untransformed austenite is known as retained austenite, which is unstable and will slowly transform into martensite over time.
    This gradual transformation can cause dimensional changes, leading to warping. Sub-Zero Processing forces this transformation by cooling the material below 0°C, reducing retained austenite to the bare minimum and maximizing martensite formation. This results in an extremely precise material structure.

Benefits of Sub-Zero Processing

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  • Sub-Zero Processing significantly improves knife performance in several ways:

    • Increased wear resistance: Reduces the risk of chipping, maintaining sharpness for longer periods.
    • Dimensional stability: Less prone to deterioration over time.
    • Long-lasting sharpness: Reduces the need for frequent sharpening.

    These advantages allow KIREAJI knives to maintain exceptional sharpness over long periods, enhancing your cooking experience.

Shiroyama Knife Workshop's Commitment

  • Shiroyama Cutlery takes pride in mastering Sub-Zero Processing technology. By carefully selecting materials and applying decades of technical expertise, they ensure the highest levels of sharpness and durability.

  • As a result, Shiroyama Cutlery's knives are renowned for their extraordinary sharpness and durability, highly regarded by professional chefs. You, too, can experience the ultimate precision crafted by these artisans.

Sub-Zero Processed Knives Available at KIREAJI

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  • At KIREAJI, you can find knives treated with Shiroyama Knife Workshop’s Sub-Zero processing. These knives are ideal not only for professional chefs but also for anyone who enjoys cooking. Experience the unparalleled sharpness achieved through advanced Sub-Zero processing—try one for yourself today. Sub-Zero processing is a highly advanced technique that significantly enhances the quality of knives. Shiroyama Cutlery is dedicated to this technology, offering knives with exceptional sharpness and durability.

  • Enhance your culinary experience with a knife that has undergone Sub-Zero processing. Please take this opportunity to try our meticulously crafted products.
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The Origin of Craftsmanship

  • Chasing My Father's Shadow

    From a young age, I grew up watching my father work.
    Seeing him forge iron in the roaring flames, shaping knives with intense focus, was like witnessing an artist at work. His presence was commanding, and his back seemed so strong, so inspiring. It wasn’t just a job—it felt like a sacred ritual, breathing life into each blade.

  • To be honest, I never thought I could master such a skill. There were moments of failure, times when I doubted myself. But every time I felt lost, the image of my father’s back came to mind, and it gave me the strength to stand up again.

  • Now, knowing that the knives I craft find their way into people’s hands, supporting their lives and work, fills me with a deep sense of pride. I started this journey wanting to be "like my father," but over time, I’ve found my own sense of purpose and pride in this craft.

  • When customers tell me, "Using this knife is truly inspiring," it’s the greatest reward I could ask for. It reminds me why I’m here—to preserve and pass on the tradition and techniques that have been entrusted to me.

  • The lessons my father’s back taught me will always be etched into the blades I create. And with every knife I forge, I continue to honor that legacy.
Sakai Traditional Craftsmen Collection

KIREAJI's Three Promises to You

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    1. High-quality Japanese Knive

    We offer knives crafted by craftsmen from Sakai City.

  • Honbazuke

    2. Genuine Sharpness

    To ensure you experience sharpness, we provide a free Honbazuke by our skilled craftsmen.

  • 3. Lifetime Knife Use

    Every knife comes with a free Saya(Sheath) for durability. We also provide paid after-sales services with Sakai City Japanese knife workshop.