[Tensho] Natural Whetstone Yamashiro-mei Koppa Stone 298g with Iyo-mei Stone

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 verify the properties and performance differences.

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 Umegahata whetstone comes exclusively from Mukonouchi-cho in Umegahata, known for its Nakayama and Koyama deposits, and from Okudono-cho, considered the birthplace of Kyoto whetstones and famed for its菖蒲谷 (Shobudani) area.

This is a set comprised of stones that do not meet mediocrity, but have increased in size. A discerning eye can identify the genuine article by the way it splits. The stone preparation was primarily carried out by trainees 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 colorful assortment of stones, so please check the images.

We encourage you to further divide the stone yourself and observe the significant differences in its properties, including the distinct coloration. (Prepare a flathead screwdriver, mallet, safety glasses, and gloves.)

Having even one soft, reddish-pink piece is a stroke of luck. (Please understand this depends on the lot.)

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

Grinding particles with directionality are arranged on the flakes, resulting in surprisingly strong sharpening power.

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

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

Historically, this is akin to replacing the 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 metals due to the overlapping flakes and the strong grinding power originating from Yamashiro Province.

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

The visible results allow for easy self-assessment and improvement of your technique, making it highly recommended.

Experienced flake users will likely discover that the “kelp attack” – using this technique – is very helpful when dealing with stubborn or overly hard stones that were previously considered unusable.

It may reignite your motivation to re-challenge previously abandoned, difficult-to-sharpen blades. It should be noted that skilled whetstone artisans typically remove unruly grain patterns during the forging process.

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

・Includes one finished 298g stone. Size is based on the outer dimensions of the box. One stone, including the outer box and rough forging stone, weighs 409g. These are stones from Iyū Province and the upper-class mines of Yamashiro Province, with miners hand-writing the name to prevent counterfeiting and mislabeling. The forging marks shown in the image are sealed in the margin. The raw stone does not have a name written on it, so please touch and judge its properties yourself. This is geared towards those with a competitive and 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 Higohō守 (Higohōmori) are approximately: 15 x 16 x 2.8~5.4 cm (thickness varies – they often overflow and bulge). Total weight including the box is approximately 409g. We have eliminated the gambling element that many customers requested. You will receive the stone shown in the picture. ・Please polish and flatten the forging marks. 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. Regarding the “Iyū Meito” whetstones, we are not involved with products that have been falsely branded or have had names added without authorization. “Iyū Meito” whetstones from around 2007 onwards are made only from coarse whetstones. For this distinction, all names other than the small ones are handwritten. We cannot answer inquiries about “Iyū Meito” stones that have been selected and manufactured by others. ・Siliceous shale from Umegahata, Kyoto City, Ukyo Ward, Yamashiro Province. #6,000~24,000 grit. It requires some skill, but it is more likely to produce a fine finish. Due to the continuous rounded striations, it is difficult to achieve a long-lasting edge or a mirror-like finish comparable to artificial whetstones, and it is good at bringing out the contrast due to differences in forging lines, materials, and carbon content. ・The harder the stone and the more refined it is, the more rock juice will be produced. Because hardness reduces self-sharpening, perform 共名倉掛け (Kyōmeikuragake) as needed 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.