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The concept of sharpness of a knife is directly related to the concept of the cutting edge, which is formed at the intersection of the two planes of its blades. A well-sharpened knife has both blades polished to such an extent that they form a very thin, sharp edge, which must necessarily have a V-shape. The essence of the sharpening process is to remove excess particles from its blades so that the edge becomes V-shaped. The easiest way to do this is to use a special device for sharpening knives. How to check the sharpness of the knife?

Rather well-known and simple is the tomato test. Try to cut a thin slice of a ripe tomato. If it can be done without pressure on the skin, and the juice stays inside, then the knife is sharp.  You can also use paper to check the sharpness of the knife. Holding a sheet of paper in one hand and the knife in the other, try to cut a thin strip of it all the way through. A blunt knife will cut the paper unevenly or not at all. You can also check the sharpness of the knife on the hair of your hand, though you should do it with caution. Move the knife along the arm along the hair against its growth, without touching the skin. A sharp enough knife will cut through all the hairs in its path in one pass, but to achieve this sharpness you can only use the special sharpening abrasives found on knife sharpening systems such as the Hapstone Pro V5, Shapton Pro and others.

When buying a knife, especially an expensive one, it is worth buying a good sharpener or sharpening set. Do not believe the stories of sellers about self-sharpening or perpetually sharp knives - they are just a marketing ploy to encourage you to buy it. No matter what material the knife is made of, over time its sharpness will disappear. Only collector's knives do not get blunt because they are always on the shelf and the only thing that threatens them is dust. Only the knife that has never been used will always be sharp.

So, any knife sooner or later will have to be sharpened, and it is extremely important to do it correctly. Obviously, no sharpener or even the biggest sharpening set will do all the work for us. It is also true that quality sharpening without a good tool is unlikely, especially if we are talking about a heavily blunted knife made of hard, abrasion-resistant steel. Therefore, if you decide to buy a sharpening stone or a device for sharpening knives, it is worth making sure that the tool you choose is fully consistent with the type of knife and the material from which it is made. Proper knife sharpening is not just a matter of removing excess steel from the blade, but a kind of art worth mastering.

Ceramic grinding stones are most often made of aluminum oxide (corundum) or silicon carbide (carborundum) and a bonding agent. These include Borid stones, Shapton stones, etc. Boride stones are easy to use and care for. Universal set of Boride stones (from 150 to 5000 grit) is made taking into account all stages of sharpening and is suitable for knives of any steel. At the same time they may have defects in the form of saw marks on the working surface or insignificant chips.

Shapton Pro stones represent the fifth generation of professional sharpening materials with the necessary density and high abrasiveness. Properly sized Shapton Pro stones allow them to be used in Hapstone Pro, Apex Edge Pro, and other knife sharpeners. Ceramic abrasives have the advantage of uniform wear and price, although they are best suited for finishing.

Diamond abrasive sharpening stones are made of diamond grit of different grit sizes. Their main advantages are high durability, strength and speed of sharpening. At the same time, they form an aggressive cutting edge, which leads to accelerated wear, formation of microcracks, chipping and, consequently, shortening the life of the knife.

The most popular natural stones for sharpening knives are the Arkansas stone and the American-made Norton sharpening stone, as well as Japanese knife sharpening stones. The Arkansas stone is a special fine-grained quartz consisting of fused crystalline grains 1-6 microns in size. If you decide to buy Arkansas, keep in mind that it does not have the abrasive scales used for synthetic materials. Soft Arkansas is used in the initial stages of sharpening, the Hard Arkansas and Black Arkansas varieties in the later stages. Translucent Arkansas is the finest of the entire line of stones and works very finely.

The Norton sharpening stones, also made of fine quartz, are considered the best for sharpening cutting tools. Norton Soft Arkansas is designed for the basic sharpening of cutting tools, Norton Hard Translucent Arkansas is for finishing sharpening or fine finishing. The main difference of Norton Arkansas Hard Oilstone from Japanese water stones is that no slurry is formed on the surface of the stone, the sharpening takes place on the surface of the stone. Oil is used as a lubricant when working with these stones. Water may also be used, but oil may not be used afterwards. The Norton Hard Translucent stones allow perfect polishing of the edge, although it takes quite a long time.

The most important parameter of sharpening stones is the grit or, simply put, the roughness of their surface. The difficulty is that there are several different grading systems used around the world to estimate the grit level of abrasives. The most common is gradation of grit according to the number of abrasive grains per square centimeter, which is used for synthetic abrasives. In this case, the grit will be a numerical value, for instance 600 grit (rougher) or 1200 grit (less rough). Another method of evaluating the grit of grinding abrasives uses the parameters "Extra Fine" (very fine), "Fine" (fine), "Coarse" (coarse) and "Extra Coarse" (very coarse), but their understanding may differ from manufacturer to manufacturer. Verbal indications of grit size can be supplemented by the parameter of the number of grains per square centimeter, but there is no unified standard ratio for them either. Some manufacturers of knife sharpening tools indicate the grit in microns, which is the most correct method, because the ratio of the grit of steel to the sharpening stone gives an idea of what happens to the structure of the metal during sharpening. There are special comparison tables of the ratio of grit markings in different designation systems.

A variety of designs and tools are used for sharpening knives, ranging from sharpening stones and mousats to complex sharpening systems and machines. Knife sharpening machines can be electric, used in industry, or they can be sleek devices, convenient for use in the home or in restaurant kitchens. The latter, for example, include the apex knife sharpener, the edge knife sharpener, the Hapstone Pro knife sharpener and others.

The main advantage of Hapstone Pro knife sharpener systems is their versatility. They allow you to sharpen knives of all shapes and sizes using abrasives of different grains and types. In addition, they are easy and convenient to use, because they allow you to maintain the desired sharpening angle at all times. With Hapstone knife sharpening systems, you can perform all stages of knife sharpening, bringing the cutting edge to perfect sharpness. Hapstone knife sharpening machines are suitable for professionals and beginners alike, as they are specially designed for home use.

The Hapstone  sharpening system is the latest development from Hapstone, and it compares favorably with its predecessors. Perhaps its main advantage, and a real gift to users, is its ability to be assembled without the use of additional tools - all assembly and installation operations can be done by hand. Also, the Hapston Pro sharpener provides increased sharpening angles (from 11 to 44 degrees). An important advantage of this model is also its reduced weight and increased stability.

We should not forget about such an important accessory for the Hapston Pro sharpening systems as the swivel mechanism, which provides for turning the knife right during sharpening. Using the swivel mechanism allows Hapstone not to remove the knife from the sharpener, thereby providing maximum convenience and reducing sharpening time. Hapstone Pro knife sharpeners are designed specifically for home use and are suitable for beginners and professionals alike.