When gold comes to mind, people most often think of yellow gold. However, many types of gold are used in the watch industry, such as white, pink, and red gold . There are also in-house alloys made by manufacturers like Omega's Sedna gold and Rolex's Everose, both red gold alloys. A unique alloy is Hublot's Magic Gold, which combines yellow gold and ceramic, making it extremely scratch resistant.
Technically, a timepiece can only be considered a gold watch if the case is made of solid gold . However, you can count watches in a lower price range as well, as their cases are made of stainless steel which is then coated in gold.
A gold watch is almost always produced from an metal alloy. Pure gold, which you find in the form of coins or bars available for purchase, is used to plate the surfaces of cases made of a different material. As it's relatively soft, some manufacturers mix it with other metals in-house in order to make it harder and more scratch resistant or to give it another hue.
A value of one karat means that the material is composed of 1/24th gold. Pure gold is thus 24 karat. Watch cases with the highest percentage of gold are 18-karat cases , a value equal to 750 gold. The 750 represents the percentage of pure gold out of 1,000. In a 750 alloy, 75% of the material is pure gold, while the rest consists of other metals. Silver and copper are mixed together with yellow gold. The amount varies, however, in order to slightly change the tone of the yellow gold.
Red and pink gold have a much larger percentage of copper than silver, which gives the gold its reddish-pinkish hue. White gold, on the other hand, has more silver than copper. Particularly valuable 18-karat white gold watches are made with an alloy containing platinum or palladium.
Cases made of 14-karat gold (585 gold) can also be found, although most manufacturers offer 18-karat gold watches today. This applies to watches in both mid and upper price ranges, such as those from Longines, Maurice Lacroix, and Tissot.
Some manufacturers use gold-colored coatings that resemble gold, but are actually something else entirely. The most common of these methods uses a PVD (physical vapor deposition) coating. During this process, the coating is applied via vacuum deposition. PVD coatings can also be made of gold and are regarded as very scratch resistant.
An alternative is electroplating gold on stainless steel cases. The gold layer is very thin; 20 microns is the norm. One micron is 1/1,000th of a millimeter. The gold plating is either 18 or 24-karat gold and prone to scratches, but can be redone if necessary. The PVD method has grown in popularity in recent years, so you will most frequently encounter electroplated watches in the vintage market.
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