Naniwa Whetstone #400 Professional Stone P-304

A top-quality coarse stone from Naniwa for fundamental sharpening and blade repair.

- Grit: 400 - Japanese water stone - Dimensions: 21 x 7 x 2 cm - Material: White aluminum oxide - Manufactured at the NANIWA factory in Osaka, Japan

Naniwa Professional Stone Series This is Naniwa’s highest-grade sharpening stone series. There are classic sharpening stones, and then there are stones that become your most valuable tools. The Naniwa Professional is one of those. An experienced sharpener looks for a stone that not only performs well but also works quickly. The Professional series is remarkably consistent and fast, making sharpening a truly enjoyable process.

With dimensions of 21 x 7 x 2 cm, this stone is nearly perfect for most knives and tools. Its single-sided thickness ensures it will last through countless sharpening sessions.

Magnesia Bonding What sets the Professional series apart from other water stones is the bonding agent used between the abrasive grains. This process, called Magnesia Bonding, differs from the resin-based bonding used in the Naniwa Superstone series. One of the key advantages is the higher density and uniformity of the abrasive particles, which gives the stone the fastest sharpening capability across the entire Naniwa range. Experienced users can truly feel the difference.

Soaking the Professional stones is optional. If you choose to soak them, we recommend no more than 15 minutes. After that, the stone is ready for sharpening. We also suggest keeping a spray bottle handy to keep the stone wet while working.

Stone Care Naniwa’s Professional stones require more care than the average sharpening stone. Unlike some water stones, these should not be left soaking in water, as it may affect the bonding structure. When you're finished sharpening, let the stone air-dry naturally. Do not accelerate drying by applying heat — just let it dry evenly in the open air. Store the stone only once it is completely dry.