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About Natural Whetstones

Whether sharpening a knife, razor, or tool using a whetstone to get the process done is a time-honored tradition. To accomplish this task, many people prefer to use synthetic whetstones with clear grit ratings and consistent results. Others prefer using natural whetstones as has been done for thousands of years. There is no reason someone cannot use both, each require different proficiencies and skills to use well. I am documenting the information I have learned as I explore these topics on this website. My goals are to help others grow their own knowledge and explore a hobby I am passionate about.

Overtime, I hope to explore many different stones from all over the world and have the opportunity to use them and report on my experiences. I hope you find the following information enlightening. Should have you have any information to add or input about the items presented, please never hesitate to contact me.

How a Natural Whetstone Works

A whetstone at first glance is a fairly simple object. An abrasive brick you run the blade on to remove metal. In many ways this is correct. However, it is missing some of the microscopic workings of the whetstone which affect how the metal is removed from the blades edge. With either natural or synthetic whetstones – what will likely do most of the cutting is the slurry the stone creates. This mixture of water, binder, and abrasive has many names such as slurry, togidoro, or mud. Regardless of name, it is formed when the stone begins to break down and releases particles of the binding agent and abrasive which mix into the water. As the blade moves through this mixture, the abrasive particles are rapidly moved around through the disturbance of the water. This action is what will remove metal from the blade’s edge.

Some whetstones are coarse enough or soft enough to use without generating a slurry. This is not ideal though. Someone sharping in this manner alone will not get a refined durable edge from their blade. We will elaborate on some complexities with the slurry in the next section.

Synthetic vs Natural Whetstones

There are many differences between natural and synthetic whetstones. These topics include price, grit, grit type, binder type, and more. We will start with the makeup difference between the two. Natural whetstones suitable to be whetstones are formed by geological changes within the earth’s crust over millions of years. These whetstones are primarily comprised of a clay-like binder with a natural abrasive pressed together within it. This claylike binder can comprise of many different substances and take many shapes. Japanese whetstones for instance look like platelets or flakes. Others such as Cretan whetstones can have oblong or round shapes to the clay binder. These shapes are naturally made, so difference in size is expected even when they share a common shape. This is part of what gives natural whetstones their unique properties. While the abrasive within the binder does the majority of the cutting, the binder plays a huge role in how the abrasive rubs against the surface of the blade and impacts how it cuts/polishes.

Synthetic whetstones are manmade with a synthetic abrasive suspended in a synthetic binding agent. The abrasive is going to take the form of a grit which is highly uniform and will be easily released from the binding agent. This quick release is one of the first distinct differences between the natural and synthetic whetstones. Synthetic whetstones will break down much quicker than natural whetstones but will also create their slurry much easier.

The abrasive in natural and synthetic stones are different in composition and hardness. Natural stones are using a form of silicone dioxide (silica) which only a bit harder than the hardened steel you are sharpening/polishing. Often you will hear people claim that natural stone slurry breakdown as you use them. There is no evidence this is true, there is evidence though that the silicon dioxide is getting smoothed out as you sharpen due to the similar hardness. This smoothing results in the slurry acting as a higher grit and feeling broken down more. A synthetic stone typically uses silicon carbide or aluminum oxide. Both of these substances are a lot harder than silicon dioxide, which is one of the reasons synthetic stones cut so much faster and do not have the range that natural stones do.

Why use Natural Whetones?

The sharpening particles of natural stones are uneven in their size due to being created naturally. When used for sharpening a blade’s edge, this will result in the microscopic teeth left over – jagged edges on the blade – being uneven. These uneven teeth wear at different rates which allows the knife to stay sharper for longer than the uniform teeth created by synthetic stones.

Additionally, the binder in natural stones is compressed and much stronger than those of synthetic stones. A natural stone will last much longer and dish out slower. A nice quality bench sized natural stone should last the average user a lifetime if not be passed along for multiple lifetimes. A natural stone will also allow for more options regarding blade polishing whereas synthetics are often a poor choice for such work unless you are working up to a mirror finish.

There is also something to be said for the history of using natural stones. If you are someone who appreciates traditional methods and how it connects us to our collective pasts, natural stones have a special place. The smell of earth they release, the traditions and methods associated with them can be a very fulfilling experience. It is a personal choice though and not for everyone, but if it intrigues you, I suggest you try one out and have a chance to experience it.

Why are Japanese Natural Stones so prolific?

When starting to look at the natural stone spectrum, it is quickly established that Japanese Natural Stones are some of the most common and desirable stones. Even looking at the spread of information on this site corresponds with that reality. Japan is home to a large portion of easily accessible stone suitable for whetstone production. This plays one of the factors in its popularity, a lot of it is available. However, and maybe more important, is the catalogued and studied nature of stones in Japan. Unlike other areas of the world which may be known for a single stone (Belgian Coticule, German Thuringian, etc.) Japan has a storied history of testing and orally passing down the knowledge of different whetstones and their properties. England is probably second inline conceptually, but still nowhere near the plentiful number of options and knowledge which stem from Japan regarding their natural whetstones.

It could also be argued that Japan has some of the finest natural whetstones available, requiring no oil (and often being incompatible with it) to achieve keen edges which other stones (Arkansas, Coticule, etc.) require oil to achieve. Combine the water-only abilities with ease of use (softer but still very fine) along with variety/stock available and it becomes clear why they are such a large part of the natural whetstone world.

Further Information

The below sections lead to additional information regarding different natural stones, blades, razors, and honing methods. This entire website is a work in progress as a hobby and not a job for me. Please excuse its incomplete nature as it is a living document, forever expanding!