Polishing exists mainly for two reasons. For technical reasons, why we polish pivots for example, and for aesthetic reasons if we polish a corner or a flat surface, even if there could be a technical reason too.

There are also two techniques of polishing, one is called “écrouissage” where we smooth the material with a burnisher. In this technique the material is polished by smoothing it, which means that it is hardened on the surface. This is the technique used to polish, or in other words to roll, the pivots. The second technique is abrasive where we come to polish with an abrasive paste starting with a rough paste and this until very fine diamond pastes called diamondines.

There are also different qualities of polishings. One is called white polish, which means that you look at the white reflection of the result to judge its quality. This is a relatively easy quality to achieve. The highest quality is called black polish, where the polished piece is tilted to get the black reflection. It is in this reflection that we will see almost all the imperfections. When we have an intact black reflection we clearly have the highest quality, which is also used in the mirrors of the highest quality telescopes.

Another technical reason, once important, is that a polished surface oxidizes less quickly than a matte surface when in contact with moisture. Various metals can be polished. Hardened steel is very suitable, but brass, german silver or gold can also be polished.

Polishing mainly appeared at first to reduce the friction in the pivots and also to harden the pivots thanks to the polishing method of work hardening.

This method of polishing by hardening has the advantage of hardening the surface and keeping the core of the part soft and therefore in a way unbreakable. The hardening of the material also improves the longevity of the part.

The polishing also appeared in the idea to slow down the oxidation process at a time when the boxes were not waterproof.

Advantages: Has a very nice aesthetic effect and can reduce the risk of oxidation and for some parts reduce friction.

Disadvantages: Can be complicated to achieve and requires especially a cleanliness during its execution.

Polishing lends itself well to the artisanal method and in fact it is where it is most used for aesthetic reasons. In particular for bevels that we can take the time to do by hand, especially with sharp edges on outgoing and even incoming angles.

Sometimes the whole thing is even refined with the help of dried gentian roots by the generation that preceded its user.

Polishing is also used in the semi-artisanal method. It will be used for technical reasons, to reduce friction in the pivots for example, but also for aesthetic reasons.

That said, this will be a simpler beveling without sharp edges on the in and out corners and will often be done with a milling cutter. However, it is possible to have polished beveling in this intermediate method and also nice renderings.

For the industrial method, a large part of the polishing is done for technical reasons. This is mainly to reduce the friction at the pivots.

It can also have polishing for aesthetic reasons but this polishing is usually white polish and not black polish.