How to create a mirror edge on a knife?

The mirror edge on the blade for many knife fans is the main criterion for high-quality sharpening and great sharpness. Although in reality, there is no direct correlation between the mirror edge and the maximum sharpness. Besides, the matte edge achieved on most excellent abrasives, such as Boride synthetic stones of the PC series, cuts as well as the perfect mirror edge. Nevertheless, for many, the ideal mirror continues to be the standard and the main task when sharpening. With the help of what abrasives can you achieve a great mirror edge?

1. Diamond bars

One of the best ways to create a mirror edge as a result of sharpening is to use diamond bars on various bonds. In particular, diamond bars on a galvanic bond can give a fairly smooth mirror surface. But they lack the softness for the highest-quality finish and fail to completely get rid of the sharpening marks. This problem is solved by using bars on an organic bond, which consists of formaldehyde resin and works much softer. For example, in the case of the use of Venev diamond stones, the best mirror is given by the bars on the upgraded OSB bond. The basis of this bond is not a standard diamond grinding powder, but a micro-powder of the ACM brand, made of synthetic diamonds of normal abrasive ability. Also in its composition, there is no boron carbide and in the manufacture of the bar, the abrasive layer on it is not sintered but glued to the body of the metal plate. All these factors, taken together, allow you to get the maximum softness of the bond. These bars are ideal for the hardest steels, primarily powder steels, and allow you to get an excellent mirror edge, almost devoid of sharpening marks on the secondary bevel. Moreover, it should be noted that you can achieve a mirror edge already on the bar 20/14 – 7/5, and the bar with a gritness of 3/2-1/0 gives the bevel a perfect finished look. Of course, as in any other cases of polishing the blade, you will need to spend the maximum time on sharpening to achieve the maximum result. But the effect of a gorgeous mirror is worth it.

2. CBN sharpening stones

An analog of diamond bars that allow you to get a mirror edge are bars of boron nitride (CBN). Cubic boron nitride is a synthetic material that is close to diamond in hardness but has higher heat resistance. It is a chemical compound of two elements — boron (43.6%) and nitrogen (56.4%), and has a crystal lattice with almost the same structure and parameters as diamond. CBN bars are produced on metal bonds, which are based on copper and tin compounds, as well as on an organic bond (bakelite) based on phenol-formaldehyde resin. At the same time, it should be noted that CBN bars on a metal bond, despite their hardness, are able to give the secondary bevel a clean mirror surface. However, as with diamond polishing, this will take quite a long time. The 3/2 bar already gives excellent results, and the 2/1 bar guarantees a clean and even mirror.

3. Naniwa stones

One of the best abrasives that allow you to get a mirror feed is Japanese Naniwa stones, primarily in their premium series - Professional Stone (Chosera).  These are synthetic stones made on the basis of aluminum oxide. Thanks to the unique manufacturing technology, these stones are characterized by high productivity, and due to their structure can be used for any steel with a hardness of up to 68 units on the Rockwell scale. Naniwa combines the softness of the bond, excellent quality of the raw material, and very fast grain renewal in the process. The main factor determining this efficiency is the unique magnesia bond of the abrasive. This bond is a magnesian cement formed by mixing caustic magnesite and a solution of magnesium chloride, and solidifies in air, at ambient temperature, without baking. One of the main features of this bond is the high density and consistency of fine abrasive particles. This gives the stone the highest sharpening efficiency among water stones. The mirror surface is achieved when working with a stone of 5000 grit (according to JIS system), but a stone of 10,000 grit (according to JIS system) gives an even greater purity to the mirror surface.

4. Dialux polishing compound with leather on the blank

A good gloss and mirror finish can be achieved by polishing on a board with leather or leather on a blank, using special pastes. The best choice, in this case, is Dialux paste, made of aluminum oxide on an oil basis. For knives, Dialux Blanc paste with a microparticle size of 20 microns is used. The paste is applied to the leather in a thin layer and during the polishing process, the abrasive particles are destroyed and the grain size of the paste is reduced to 2 microns. Polishing with paste on a leather blank using TSPROF sharpeners requires quite a long time of work and concentration. The leather blank should only lightly touch the surface of the bevel and move strictly along its plane. Do not allow the cutting edge to deform and create a lenticular surface. If these rules are followed, the mirror after the skin with the paste turns out to be smooth and shiny. 

5. Diamond compound on an oak blank

Another way to obtain a mirror edge is the use of diamond polishing pastes, for example, pastes of the Venevsky Industrial Diamonds. The paste is made on the basis of synthetic diamond powder, a binding fat base, and surfactants. It has a thin ointment-like consistency, so it is easily distributed over the entire surface to be treated. When working, it has not only a mechanical but also a chemical effect on the material. The surfactants that make up the paste remove the slags and chips formed during the polishing process from the processing zone, and facilitate washing. For use in TSPROF sharpeners, the paste is applied to a blank with a firm and even surface, we recommend the use of an oak blank. The effect of a mirror cutting edge occurs already when using a paste of 7/5 HOM, the maximum effect is given by pastes of 3/2 HOM and 1/0 HOM. The compound almost completely removes the sharpening marks.

In addition to the methods described above for obtaining a mirror edge, there are others. To achieve a good result, you can also use natural sharpening stones, such as Belgian shale. However, due to the extraneous inclusions and heterogeneity of such stones, achieving the perfect mirror requires a very large effort.