|The Care and Use of Natural Waterstones
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 Japan Woodworker 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 Stones are for initial sharpening and are inexpensive because they are in great supply.
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.
Medium Stones remove the scratches left by the Coarse Stones and are slightly more expensive.
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.
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 is 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
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.
Below is a drawing of a Japanese-style base which is used to hold waterstones steady during sharpening. The base is easy to make, and the user can vary the design to suit his or her taste. Redwood or cedar is typically used. However, any water and warp resistant wood is suitable material.
Revised May 2013