[Tensho] Natural Whetstone Yamashiro-mei Koppa Stone 224g with Iyo-mei Stone

Locally Sourced, Locally Made – The Power of the Earth!!

Box dimensions are shown above. Weight indicated is the packaged weight. Please refer to this for size comparison.

The grain is clear, making it easy to work with and yielding a high rate of usable material when dividing the stone. We encourage you to actually try dividing and shaping the stone yourself to verify the properties and performance differences.

It includes a variety of types, sizes, and shapes. For blades you intend to sharpen, use a stone with ample size to create a flat surface. Otherwise, divide the stone into smaller pieces and use it similarly to sharpening Japanese swords.

It is composed exclusively of **first-class mineral deposits** from the easternmost part of Kyoto City, Ukyo Ward, along with comparative samples.

The Umegehata whetstone comes only from Mukonouchi-cho in Umegehata, known for Nakayama and Koyama, and extending to Okudono-cho, the origin of Kyoto whetstones, and the renowned Shobudani Valley.

This set features stones that haven’t been bulked up with inferior material; the quality is evident in how they break. The stones were primarily trained by apprentices under the supervision of an instructor with over 15 years of experience in the Yamamoto forging technique. We believe the results are excellent, as shown in the images.

We encourage you to try dividing the stones yourself and observe the significant differences in their properties, including the vibrancy of the colors. (Prepare a flathead screwdriver, mallet, safety glasses, and gloves.)

Having even one soft, reddish-pink stone is a stroke of luck. (Availability varies by lot, we apologize.)

From the genuine stone with a clear grain, a film-like slurry easily emerges.

The abrasive particles are aligned on the flakes, resulting in surprisingly strong sharpening power.

The particle size increases as the flakes break down under reduced water flow.

The sliding between flakes is lubricated by the crushed mud of tenacious feldspar and mica minerals, creating a smooth gliding sensation.

Historically, it’s akin to replacing the konbu (kelp) used to slide heavy stones for Osaka Castle’s walls with crushed flakes.

Excessive pressure when sharpening with too many unbroken flakes can create shallow scratches on softer steels due to the overlapping flakes and the strong abrasive power originating from Yamashiro Province.

Adjusting the pressure, sharpening angle, slurry amount, and water flow will improve your technique and reduce these scratches.

The visible results make it easy to self-assess and improve your skills, making it a recommended approach.

Experienced users of flakes will likely discover that the “konbu attack” – using this technique – is very helpful when dealing with stubborn or hard stones from other regions.

It may rekindle your motivation to re-challenge previously abandoned, difficult-to-sharpen blades. It’s generally the responsibility of a whetstone artisan to remove unruly grain through forging, but…

The market tends towards shortcuts in manufacturing, prioritizing thickness and size for higher profit margins, so there will likely be opportunities to use the soft, reddish-pink slurry.

・Includes one finished 224g whetstone. Size is indicated as the outer dimensions of the box. One whetstone, including the outer box and rough forging stone, weighs 503g total. These are whetstones from Iyū Province and Masuyama/Yamashiro Province, ranging from mid- to high-grade, and feature miner-applied inscriptions to combat counterfeiting and mislabeling. The forging marks shown in the image are sealed within the margin. There are no inscriptions on the raw stone, so please assess its properties by touch. This is geared towards those with a competitive or training-oriented mindset. ・Neutral and rust-resistant whetstones from Tangawa Village, Iyū Province, revived after half a century! https://bit.ly/IyoMIkantsubu The outer dimensions of a 10-stone box of Higo-no-kami (approximately): 15 x 16 x 2.8~5.4 cm. Thickness varies. (It often overflows and bulges.) Total weight including the box is approximately 503g. We’ve eliminated the gacha element – you’ll receive the stones shown in the photos. ・Please polish the forging marks to create a flat surface. If the stone is unstable, apply a wet cloth or secure it with silicone adhesive to a non-deformable base. Mining is done with heavy machinery, and cutting is done with diamond tombstone cutters. We are not involved with imitation products bearing the “Iyū Meito” mark. “Iyū Meito” whetstones produced since around 2007 are made only from sazareshimei whetstones. All inscriptions other than the small ones are handwritten to distinguish them. We cannot respond to inquiries regarding “Iyū Meito” stones selected and manufactured by others. ・Siliceous shale from Umegehata, Kyoto City, Ukyo Ward, Yamashiro Province. #6,000~24,000 grit. Relatively hard, requiring some skill, but with a higher probability of achieving a fine finish. Due to the continuous rounded striations, it’s difficult to achieve a long-lasting edge or a mirror-like finish comparable to artificial whetstones, and it easily reveals differences in forging lines, material, and carbon content. ・The harder the stone and the more rock dust it produces, the finer the finish. Because hard stones have lower self-sharpening ability, you’ll need to perform kumakura-gake (compound application) as needed while sharpening, depending on your purpose and skill level.

【Voltage Compatibility】 When using electrical appliances, please note that they are designed for Japanese voltage specifications (90-110V), so if you use them with a different voltage, it may cause a malfunction.

【Plug Type】 Our products use Japanese plug types (A or B type). Please use a conversion adapter if necessary.

【Important Note on Transformers and Adapters】 A transformer adjusts voltage to match your device's requirements. A conversion adapter only changes the plug shape and does not adjust voltage. Using only a conversion adapter without a transformer may result in damage to the product.

【Liability】 We are not responsible for malfunctions or damages caused by improper use, such as operating the product without a transformer.