On the other hand, the surfaces of knives that have been looked after may blacken a little, but this is a different type of iron oxide than ordinary reddish rust. This black oxidation is mainly triiron tetraoxide (Fe3O4). It coats the surface of the metal and prevents ordinary rust from getting in. It will not discolor food and poses no threat to hygiene.
Sharpening is really two processes: Grinding and honing. Grinding is simply the removal of metal. Honing is a precision abrasion process in which a relatively small amount of material is removed from the surface by the means of abrasive stones. Once you have the right shape, usually using a more aggressive grit, you then switch to a finer grit to hone the edge.
Although it is slightly expensive than other tool sharpeners, this one saves you quite some precious time. It is one of the fastest ways to get all your blades sharpened. In addition, you just need to spend a few hours with it, and you will learn its entire operational procedure. Avoid excessive sharpening, since it might leave scratches on the blade’s surface.
The word “Novaculite” is derived from the Latin word “novacula”, which means “razor stone” and is essentially a metamorphic, recrystallized, variety of Chert composed mostly of microcrystalline quartz that is found in the found in the Ouachita Mountains of Arkansas and Oklahoma and in the Marathon Uplift of  Deposited in the Devonian Period and the early Mississippian Subperiod some 410 to 325 million years ago and subjected to uplift and folding during the Ouachita orogeny of the Atokan Epoch (early Pennsylvanian Subperiod), Novaculite is a very tough stone that is resistant to erosion and thus, the various layers of Novaculite stand out as ridges in the Ouachita Mountains. Thus, due to both its availability and its composition, it has been mined since ancient times for use as arrowheads and spear heads as well as in more modern times for use as sharpening stones.
Place an old coffee mug upside down so that the bottom of the mug is exposed to the air. In a pinch, a coffee mug can serve as a surprisingly effective sharpening tool if you don't have any fancy equipment. The ceramic material of a mug is a material coarse enough to get good results. Indeed, some honing rods even use ceramic material to keep a blade homed in between sharpenings.

Fortunately our product review experts have put their noses to the grindstone (so to speak) for you and come up with a comprehensive list of the 14 best knife sharpeners on the market today. They’ve cast a wide net that includes everything from the most elaborate mechanical devices to the simplest sharpening sticks and stones so you’re bound to find one that fits your needs, temperament and budget. Keep in mind that any opinions expressed here are those of our experts.

Sharpening stone/whetstones. Just as there are dozens of different ways to sharpen a knife, there are dozens of different sharpening stones. There are Japanese water stones, stones with diamond encrusted surfaces, and stones with different grades of grit. Again, choosing a stone is a matter of function and preference. Play around with different kinds of stones to find the one that gives you the results you’re looking for.

Authentic Japanese Combination Whetstone which has the finest medium grey #1000 Grit on one side and a lower grade of 240 Grit on the other. It can be used for most type of knife such as cleaver, fruit, and sushi knife. This type of whetstone is recommended by many professional chefs to achieve ultimate sharpness of the knife. Use this whetstone also to sharpen your weaponry collections of Samurai Swords, Kama, etc.

Both Belgian Blue and Vielsalm Coticule are ancient stone layers found in the Belgian Ardenne Mountains with characteristics similar to both Novaculite and Siliciclastic sedimentary stone in that it is a metamorphic stone consisting of both gray and yellow volcanic ash mixed with tiny Spessartite Garnet crystals suspended in a clay matrix. However, due to its geology, both types of stone occur only in vertical seams sandwiched between two thick layers of bluish-purple slate and thus, they must be meticulously extracted mostly by hand. However, this type of extraction process is both very time-consuming and very labor-intensive and, quarrymen can only extract the stone for a few months each year due to inclement weather conditions. Consequently, both Belgium Blue and Coticule whetstones tend to be somewhat expensive.