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Okudo Tomae Stratum Natural Sharpening Stone Class A

Item 162142

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  • Okudo is a semi-active (Higashi Mono) Kyoto whetstone mine that is best known for the most highly coveted Suita in Japan. Higashi Mono means eastern mines of Kyoto. Tomae identifies the Strata that the stone comes from. Nest Plate is the stratum that the stones come from. There are...

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    Okudo is a semi-active (Higashi Mono) Kyoto whetstone mine that is best known for the most highly coveted Suita in Japan. Higashi Mono means eastern mines of Kyoto. Tomae identifies the Strata that the stone comes from. Nest Plate is the stratum that the stones come from. There are several different stratum. We stock Suita, Tomae and Aisa. The Tomae being in the middle section of the quarry. Most of these stones have Su – small holes or pockets created by escaping gas when stones are forming in the earth's crust. These are not are not imperfections, as they do not interfere with the honing process.

    The Tomae stone is a medium hard stone, that has exceptional properties for final honing of kitchen knives and chisels. Not typically hard enough for razors.

    This medium hard stone will create its own slurry with a minimal amount of water. Naguara stones can be used to increase the slurry.

    The Class A stone has very little imperfections.

    You may be curious as to the markings on the stones. The top left indicate the mine (Okudo). The bottom left indicates the Stratum (Tomae). The numbers on the sides are simply for inventory purposes by the mine.

    We have been working with our partners in Japan to get a consistent natural stone. Although Class A and B stones account for less than 10% of all stones mined, we are confident that we can provide these on a consistent basis. All of these stones will be a minimum of 65mm wide and 100mm long. These are a naturally occurring material and cannot be exactly as depicted in the photograph.

    Sharpening stone material has been mined in Japan for nearly 2,000 years. About 1,200 years ago, the best deposits were discovered in the mountainous Narutaki District north of present day Kyoto. Over the centuries, the easily obtainable deposits have been mined out. Today, laborious tunneling and mining techniques are required to obtain natural sharpening stones. All of the natural stones sold by the Woodcraft have been selected following a centuries old grading method. Particular care is taken to ensure that we obtain stones of a more uniform size and quality than those generally available in Japan.

    Basically, there are three categories of natural Japanese waterstones and numerous gradations and quality levels within each category. Coarse, Medium and Finish Stones. We only stock Finish Stones. Many craftsman choose to use synthetic stones to prepare a damaged or very dull tool. Choosing to use the more expensive natural stone for the final sharpening/honing.

    Finish Stones are used for final polishing to produce a razor-sharp edge. Finish Stones are in short supply and can range in price from an amount similar to a synthetic Finishing Stone to over $2,000 for the finest polishing stones used for sword polishing. Finish Stones do not produce a mirror bright finish as do the synthetic stones. Japanese craftsmen believe the mirror finish obscures the surface of the bevel and does not allow as fine a determination of its flatness and sharpness.

    In addition, the Finish Stone brings out all of the beauty of the lamination lines in the soft metal (Jigane) of the better quality plane irons, much as the temper line in the Samurai sword is brought out by polishing.

    As you become familiar with your Finish Stone, you may discover two or three different honing actions related to specific areas on the stones. This is typical of even the most expensive stones. In fact, you may discover you prefer to hone one tool on a certain area of the stone and another tool on yet another area. Our natural finish stones will give a better finish than any artificial stone.

    Preparing Natural Stones for Use

    Before initial use, the sides and bottom of all natural stones should be painted with several coats of weather-resistant lacquer or varnish. This coating is necessary to prevent the natural stone’s layers from fracturing. These layers were formed over millions of years of geologic action that resulted in no two stones being exactly the same. Natural stones may contain hidden faults or spots which may not be as fine as the rest of the stone. In this case, use a nail to scrape the spot or line slightly below the surface of the stone.

    To ensure the Finishing Stone’s incredible polishing action, it may be necessary to use a Nagura Stone to create “mud” or paste on the stone’s edge before honing begins, thus speeding up the polishing process. In addition, the Nagura Stone makes the stone surface slipperier, which keeps the tool from sticking. Simply rub the Nagura Stone in a circular motion on the full surface of a Finish Stone until a paste or “mud” develops. If the stone surface is too dry the Nagura Stone will stick. To alleviate this problem, add a few drops of water. Generally speaking, the more paste, the better the honing action.

    Flattening Your Stones

    The stones stocked by Japan Woodworker are ground flat and prepared with a slight bevel on the edges, but should be checked prior to use to ensure they are ready for use.. Before initial use, all stones should be flattened after soaking for a short period of time in a water bucket. The Medium Stone can be flattened on #220-grit wet/dry sandpaper. The Finish Stone can be flattened on a Coarse Stone which has been previously flattened. Be sure to place a narrow bevel (approximately 1/32" to 1/16" wide) on all edges of your stones by rubbing the edge on the wet/dry sandpaper at a 45° bevel. The reason the edges are beveled is to prevent pressure flaking, which can chip off flakes of material from the sides of the stone.

    After the scratches have been removed by the Medium Stone, the final step is to hone the edge on the Finish Stone until the wire edge disappears and the bevel is well polished. After use, natural stones should be placed on a rack out of the wind and sun and allowed to thoroughly dry out before being stored. With careful use, the more expensive Finishing Stones will last several lifetimes.

    Natural Stones Should Only Be Lubricated With Water!
    Oil or other mineral spirits will destroy the sharpening ability of the stone. Natural stones should not be immersed in water for long periods of time, as this could cause fracturing along naturally occurring fault lines in the stones.

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