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Every time, the "Experts talking" column develops a different case.
The author's aim, as connoisseur and authority about the matter, is to help you to understand the subject by making these informations comprehensible and digestive.
Presently: Material and finishes for watch cases

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- Material and finishes for watch cases

- Watch Professionals I
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- Bevelling and finishes...(VII)
- Bevelling and finishes...(VIII)
- Bevelling and finishes...(IX)
- Bevelling and finishes..(X)
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The author

Expert in communication and marketing, Pierre F. Brenzikofer was for more than 25 years in charge of the Marketing-Services of an important swiss watch group. He had a deep knowledge of watches communication. He was very active in professional basic and further training, and invested a lot of energy in the management of training centers and the setting up of modern didactic instruments.

6. MATERIAL AND FINISHES FOR WATCH CASES

The watch manufacturers make use of many materials in the production of watch cases. We believe the following information about case materials and finishes will be of practical help for the consumer. The case (together with the glass, the bezel and the strap) has two functions : Protection of the movement against impurities, water and shocks and external aspect which gives the watch its own personality.

 


Extract from the trilingual "Lexique du Génie Horloger"


The following presentation shows the characteristics of the main materials used in the production of watch cases.

Stainless steel
Stainless steel on its own or combined with a yellow metal is certainly still the most popular material for the cases of quality watches. Steel is a tough material which does not deteriorate if knocked or scratched. It is an alloy (iron and carbon) that can be given a good polished finish and it does not corrode.

Gold-plated
The cases of gold-plated watches are shaped out of a base metal like brass and then dipped in a bath where a layer of gold is electro-deposited on them. The thickness of the layer of gold on a swiss gold plated quality watch will normally be 10 or 20 microns (10 to 20/1000 of a millimetre). Gold-plating of this thickness should remain in good condition even if it is subject to a certain amount of friction, for instance from a shirt cuff. As perspiration can damage goldplating, the backs of quality gold-plated watches a normally made of stainless steel.

Platinium
Platinium used in watch cases is a fairly hard precious metal with a silvery-white colour and is unexpectedly heavy to those not accustomed to handling objects made form it. It does'nt oxidize by high temperatures.

Gold
Clearly the best known precious metal used in watches cases is gold. In addition to its value, gold has the advantage of keeping its colour and not oxidizing. Gold is a soft metal and has to be alloyed to other materials. Naturally the higher the gold content, the more valuable the case is. The gold content is quoted in carats or "karats", with 24 carats equalling 100% gold. One gold carat means 1/24 gold in the alloy. 18 carats means that that 18/24 of the alloy consists of fine gold. The colour of gold depends on the metals with which it is alloyed (gold, silver, nickel, copper, palladium) : the final colour will be white, yellow or rose gold.

 

 

Silver
Form time to time manufacturers introduce collections of silver watches. Tarnshining is a problem with this precious metal as it needs to be polished regularly to keep its shine. However, forms of surface treatment have been used in an attempt to overcome this. The silver content is quoted in thousandth : in Switzerland, the legal quotes are 925/1000 and 825/1000.

Titanium
Titanium is an exciting space-age noble material. It is particularly prized for its very high strength/weight ratio. Although its price is up to 10 times more expensive than stainless steel and is costly to machine, it offers distinct benefits when used in watch cases : titanium is antimagnetic, it does not cause allergies and is anti-corrosive. It is light, rigid, chemically neutral and non-toxic. Titanium has a velvety pearl-grey colour and texture which changes with the light. The scratches no longer stand after a few days.

Hard metals
In recent years several Swiss quality watch manufacturers have adopted new materials in the form of hard metals made from soft metallic tungsten or titanium carbide powder. Cobalt is added to this powder. The powder is pressed into a shape, sintered and heated up to a very high temperature (1300 to 1500C). The resulting shell is machined and finally polished with diamond tools. The end-result is a very hard and very highly polished case resisting scratches and keeping its fine initial appearence.

Rhodium and chromium-plated
Rhodium is a rare metal, rather hard, highly reflective used to plate lower-priced watches. It looks more or less like platinium. It is harder than the base metal it is used to coat. Chromium is a white metal that is also used to coat lower-priced watch cases so that they resist rut and wear.

Finishes
During the manufacturing process, cases can be given different kinds of finish. For instance, they can be polished to give them a mirror-like shiny surface. They can be given a brushed finish, in which the surface is marked with very thin parallel straight or circular lines or lines in the form of spirals. These all are decorative effects. The latest kind of finish is described as "shot-blasted" or "micro-balled".

The case is held under a very fine jet of minuscule glass balls which bombard the surface and give it a special mat effect.

Other materials
There are of course other materials than these presented above used in the manufacturing of watch cases, such as aluminium, wood, rubber, granite, ceramic, plastic. These cases, mostly fashion oriented, have all their own manufacturing processes and characteristics.


 

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