Gold, in its natural form, is soft, dense, and inert. It also has a yellow sheen that is rather garish by today’s discreet luxury standards. In the watch industry, gold is often mixed with other metals to make it stronger and more resistant, creating what are called gold alloys. Mixing also changes the colour of gold; depending on the types and amounts of metal added, alloys can range from red-gold to brilliant white.
The measurement unit used for the purity of gold is the karat (k). Gold that is labelled 18k, for instance, is composed of 75% gold and 25% other metals. Gold that is certified 24k is pure gold without any metals added. Note that the higher the karat, the less hardy the gold is, and vice versa.
In general, Swiss manufacturers never use anything lower than 18k gold. This is also the point where gold can start to adopt different colours. In a bid to boost their stature, some manufacturers, like Hublot, have even gone as far as innovating and patenting their own gold variants.
Red Gold/Rose Gold/Pink Gold
Red gold essentially comprises gold and copper. The amount of copper used dictates the colour intensity of the gold.
Although the term "red gold" is sometimes used interchangeably with rose gold or pink gold, the latter two actually contain a hint of zinc, which makes for a more subdued shade. If you’re a wine lover, it is something akin to the difference between a rosé and a red wine.
This colour is achieved by mixing gold with one or more white metals. In fine watchmaking, the metal used is often palladium, a close cousin of platinum. The finished product is usually coated with rhodium to achieve the desired brilliance, as white gold, on its own, actually looks dull and grey.
Ceragold and Sedna Gold
Ceragold was created by Omega for the bezel of the Seamaster Planet Ocean dive watch. Essentially, the process involves rings of zirconium oxide, onto which diving scales have been engraved, being plunged into an electrolytic 18k gold bath. They remain submerged for 48 hours while the gold bonds with the ceramic. Excess gold is then removed to recover the black ceramic surface, leaving solid gold forming the diving scale. The brushed gold makes for a striking contrast against the polished ceramic, but the entire surface is absolutely smooth to the touch.
Another trademarked gold creation by Omega is Sedna gold, which has appeared in its Constellaton watch. This gold alloy is made with a particular percentage of copper and palladium, for a unique rose gold lustre that promises to last for a long time.
Magic Gold and King Gold
As Hublot's philosophy is the Art of Fusion, gold offers the manufacturer a fantastic canvas on which to mix things up. When its Magic Gold was first unveiled, it was hailed as the first 18k gold to be completely scratch-resistant. Created at Hublot's foundry in Nyon, Magic Gold is achieved by injecting boron carbide (a type of ceramic) with molten 24k gold. Hublot claims that Magic Gold is so tough that only a diamond can scratch it!
While Magic Gold has an industrial-looking yellow sheen, King Gold boasts a shade that is more fiery than that of standard 18k 5N red gold. This results from increasing the percentage of copper in the alloy from the usual 20.5%. Platinum is also added to the mix to stabilise the colour for the long run.
One of the best-looking rose golds in the market comes from Rolex. Its brand-exclusive Everose gold has a luxurious pink hue that results from the combination of pure gold with a secret percentage of copper, which gives it its unique warm colour, and a hint of platinum, to ensure that the colour doesn’t fade in years to come.