[Tensho] Natural Whetstone Yamashiro-Mei Koppa Stone 186g[Tensho] Natural Whetstone Set with Iyo-Mei Stone (10 stones, 444g total)

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

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 experience and verify the differences in the stone’s properties and performance.

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

The Umegehata whetstone comes exclusively 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 they have successfully split, sorted, and created a diverse range of colorful stones, so please check the images.

We recommend further dividing the stones yourself to observe the significant differences in their properties and the striking variations in color. (Prepare a flathead screwdriver, mallet, safety glasses, and gloves.)

Having even one soft, reddish-pink stone is a stroke of luck. (Availability depends on the lot.)

Clear, visible grain in the original stone easily produces a flaky, mud-like slurry.

Sharpening particles with directional properties are arranged on the flakes, resulting in surprisingly strong sharpening power.

The grain size increases as the flakes break down under limited water flow.

The friction between the flakes is lubricated by the crushed slurry of sticky feldspar and mica minerals, creating a smooth gliding sensation.

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

Excessive pressure during sharpening with too many unbroken flakes can create shallow scratches on softer steels due to the overlapping flakes and the strong sharpening 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 flake users will likely appreciate how the “konbu attack” – using the flakes to tackle stubborn, hard stones – can be very helpful as they progress.

It may rekindle your motivation to re-challenge previously abandoned, difficult-to-sharpen blades. Ultimately, removing the thickness and unruly grain through forging is the domain of master whetstone artisans…

The market tends towards shortcuts in manufacturing, prioritizing thickness and size for higher profit margins. This means there’s a good chance you’ll frequently encounter opportunities to use the soft, reddish-pink slurry.

・Includes one finished 186g stone. Size is based on the outer dimensions of the box. One stone, including the outer box and rough forging stone, weighs 444g total. These are stones from Iyū Province and Masuyama/Yamashiro Province, mid-to-high grade whetstones, with miners hand-writing the name to combat counterfeiting and mislabeling. The forging shown in the images is sealed with extra space. The raw stones do not have names written on them, so please assess their properties by touch. This is geared towards those with a competitive or training-focused, avant-garde approach. ・Neutral and rust-resistant whetstones from Tangawa Village, Iyū Province, dating back to the Edo period – revived after half a century!! https://bit.ly/IyoMIkantsubu The outer dimensions of a 10-stone box of Higo-kami (approximately): 12 x 15 x 2.8~5.4 cm. Thickness varies. (It actually overflows and bulges.) Total weight including the box is approximately 444g. No gacha elements – you’ll receive the stones shown in the photos. ・Please polish and flatten the forging. If it doesn’t sit well, 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 products that falsely claim to be “Iyū Meito” whetstones due to unauthorized branding. “Iyū Meito” whetstones from around 2007 onwards are made only from sazaře meito. All markings other than the small ones are handwritten to distinguish them. We cannot answer inquiries about “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. The continuous circular scratches make it difficult to achieve a long-lasting edge or a mirror-like finish comparable to artificial whetstones, instead highlighting the forging line, material differences, and carbon content variations. ・The harder the stone and the more refined the slurry, the more likely it is to be a fine-grained stone. Because hardness reduces self-sharpening, perform regular komakura-gake (compound application) depending on the purpose and skill level while sharpening.

【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.