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Presently: Bevelling and finishes in top-of-the-range watchmaking (IV)

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The author

Having acquired an educational background in economics and literature, Caroline Sermier fell in love with watchmaking right from her arrival at Renaud & Papi.
Her current responsibilities as head of the communication department allows her to blend a taste for writing with her fascination for complicated watches, and particularly for the finishing and decorative details on top-of-the-range luxury watches.

15. Bevelling and finishes in top-of-the-range watchmaking (IV): flat polishing



Flat polishing or specular polishing

Preamble :
A number of articles have been dedicated to the fundamental notions of high-end finishes. Above and beyond the complication of the movement and its technical reliability, it is the level of finish that makes all the difference.
As explained previously, a complicated watch is not necessarily a top-of-the-range watch. In order to achieve perfection in a watch, each detail is taken into account so as to achieve the finest result in terms of quality of finish and aesthetics.
We have listed the various types of high-end finish (graining, polishing, milling, matt appearance, bevelling). Nonetheless, we should specify that some elements play a determining role in terms of aesthetics and enable us to distinguish between the various degrees of high-end finish.
According to the state of the surface achieved, an expert eye will be able to define the working method used, sometimes constituting a genuine quality label for the finish. In order to provide more concrete information, we will deal in more detail with certain issues and types of decoration which might appear superfluous or even insignificant to the layperson, but prove extremely important for the connoisseur.
Nota bene : ... by black polish or specular polish, which is the final decorative touch but is particularly spectacular in aesthetic terms (see opposite).


Flat or black polishing
Polishing and smoothing consist in reducing the roughness of the surface of the matter with the help of various tools and materials.
By means of these procedures, the crystal tips of the surface of metals are partly removed and partly squashed down into the hollows.
These finishing techniques give the treated surfaces a smooth appearance, which may result in the specular or black polish.
At the top of the range, for certain parts such as repeater hammers, indexes, endpieces or tourbillon bridges, the visible surface must have this specular polish.
This is a particularly spectacular type of decoration. The luminous reflections give more depth to the entire movement .


The use of specular or black polish :
Specular polish or black polish serves first of all the practical purpose of reducing the risk of oxidation, but this extreme form of polishing plays a primarily aesthetic role.
This procedure can achieve fascinating and indeed unique optical effects.
Once the parts are assembled, the way the watch is turned towards the light can result in reflections that are white*(photo 4),grey *(photo 5) or black * (photo 6), creating kaleidoscopic luminous effects.


Flat polish or black polish : the method
The polishing operation enabling one to achieve this state of surface, giving a mirror-like appearance to parts, is called flat polishing or black polishing.
Flat polishing or black polishing is part of the decorations that are particularly representative of the top of the range and require dexterity, patience and tremendous cleanliness.
There are various tricks of the trade and ways of doing things, but we will mention only the main ones :
- the modern method
- the high-end method

1)The modern method :
In this case, rigid abrasive papers are used (such as aluminium oxide) resulting in a part that is shiny but not transcendent in optical terms, since the surface is not perfectly smooth (not black polished).
This method takes only between 10 to 20 minutes.

2)The high-end method :
a) Preparation

First of all, the goal is to achieve a perfectly smooth surface by using rough abrasives to rub down down a part stuck to a base resting on three points of support * (photoA and photo B).
b) Polishing
The next stage is to strive for perfection in polishing by rubbing the part with a very fine abrasive (diamond paste) on a zinc plaque that has been carefully straightened flat and rid of all impurities that might embed themselves in the matter and scratch the part *(photo C).
This method calls for two to five hours of work and a great deal of care.
The aim of the operation is to make the surface of the part extremely smooth and polished in order to achieve a luminous reflection virtually perpendicular to the face, hence the black zones which are not only very difficult to achieve but also exceptionally beautiful.
At the opposite end of the spectrum, the modern method does not create any emotions, since the parts are shiny but with no highlights due to the rounded angles and the lack of levelness of the surface (the reflections point out in all directions).


Conclusion :
A specular or black polish calls for a great deal of time and care, and the cost of parts is thus considerable higher than polishing on paper. For all these reasons, companies often choose the modern polishing method, considering it to be satisfactory but above all fast and less expensive.

See: Bevelling and finishes...(III)




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