Watchmakers live in a material world, whether it’s to boost the physical properties of their products or open up new design possibilities. The materials in question can be non-metals (carbon, ceramic, sapphire or resins, appearing over the past twenty years or so) or metals – with or without “precious” credentials, and with more alliances than a season of Game of Thrones. Which is surprising, considering that when it comes to a watch’s habillage – case, dial, bezel, hands and crown – very few metals make the grade: gold, platinum, titanium and steel, sometimes silver and bronze and, very occasionally, tantalum and palladium. Watchmakers know that not every metal has the requisite qualities. “A metal has to resist friction and variations in temperature. It can’t be prone to tarnishing, must be non-corrosive, suitable for machining and, obviously, non-toxic. Arsenic and nickel are out of the question, and we’re seeing less use of lead as an additive to facilitate machining,” notes Andreas Mortensen, who lectures in metallurgy at the Federal Institute of Technology (EPFL) in Lausanne.
Even so, there’s plenty to keep it interesting. “Since the early 2000s, customers in the market for a luxury watch have learned to appreciate the less conventional alloys. At the same time, ongoing research into traditional alloys enhances their properties,” says Dr. Mortensen. New alloys are introduced on a regular basis, such as Omega’s Ceragold, a combination of gold and ceramic, or the Magic Gold that Hublot developed in conjunction with EPFL – just two of the brands concocting their own alloys. Francis Simonnet, director of Les Boîtiers de Genève, a case manufacturer, adds that “new machining technologies are constantly being developed such as laser or new software features. They open up vast possibilities for working with metal and in particular for creating new case shapes.”
Gold's multiple dalliances
All that glitters… gold has more qualities than even the most eligible bachelor and has been prized for thousands of years. For the Ancient Egyptians, who were mining gold 3,000 years before our era, it symbolised the sun. Its advantages in watchmaking are innumerable, which explains why solid gold or gold plating has been used in spring-driven watches and clocks ever since they existed. Gold will not corrode or oxidise. It cannot be altered by acids or bases, and therefore qualifies as a “noble” metal. A watchmaking match made in heaven!
Too malleable to be used pure, gold is combined with silver, copper, zinc or palladium to achieve the necessary hardness. Combining gold with other metals also alters its natural pale yellow colour, becoming a stronger yellow, pink, red, white, green (green gold also occurs naturally), violet, even blue (through oxidation of the iron atoms on its surface after heating). Gold is an endless inspiration for watch brands in the competition to create the most attractive, resistant alloy. The recipe for Rolex’s proprietary pink gold is a jealously guarded secret. Its name, Everose, promises an everlasting sheen.
Component manufacturers also love gold because it melts “like water”, pouring itself into the desired shape. “Perfectly amalgamated molten gold facilitates surface polishing, as does the fact that gold isn’t a hard metal,” explains Francis Simonnet. “On the other hand, heat-deformed gold will try to spring back into its old shape. White gold is the most problematic alloy.” Patek Philippe, which manufactures its own gold cases, appreciates “this very beautiful metal that is much easier to work with than others, such as platinum.”
Sure to stick around
Which brings us to another favourite. Like gold, platinum is a noble metal. White or grey-white in colour, it is highly resistant, dense, virtually inalterable and doesn’t tarnish. A paragon of virtue? Not quite. Platinum is notoriously difficult to machine and polish. “There is no such thing as platinum nuggets,” reveals Francis Simonnet. “Platinum comes from refined earth as a flour-like, explosive substance. Unlike gold, it cannot be perfectly melted. It has a microbead structure which makes it highly abrasive. After melting, it has to be crushed in order to amalgamate the tiny grains. Any air left between them, and polishing becomes even more problematic. Platinum must be polished slowly over a long period so as not to catch these grains, as this would create an unwanted dimpled effect. The hard part isn’t creating a lustre. It’s removing micro-defects from the surface.”
As if this weren’t enough, “because platinum is resistant to oxidation it doesn’t become covered with oxides, hence its metallic atoms are more inclined to ‘stick’ to other materials, as a result of friction during polishing, for example,” says Andreas Mortensen. Patek Philippe confirms platinum’s “uncooperative” side: “Tools become worn faster on platinum because of its abrasiveness and stickiness. We use three times as many tools to manufacture, assemble and finish a platinum case compared with gold.” When working on the Grand Seiko Masterpiece Collection Spring Drive Cal. 9R02, Seiko’s Micro Artist Studio developed “tools from specific materials rotating at specially adapted speeds. Traditional polishing tools are too hard and cannot guarantee the case’s precise dimensions. Polishing by hand also requires perfect control of the amount of pressure applied to the tool.” The result is the original snowflake decoration on the case and dial.
So, gold or platinum, the choice is yours!