White gold, a popular choice for fine jewelry, is not a naturally occurring metal. Its crisp, silvery appearance results from a specialized manufacturing process that transforms gold’s inherent yellow color. This metal is created through a combination of various elements and a final coating to achieve the bright, icy white hue consumers desire. Understanding white gold requires looking at how gold’s purity is measured and what non-gold materials are mixed in to change its fundamental shade.
Understanding Gold Purity and Karats
Gold purity is measured using the karat system, which is based on 24 parts. Pure gold (24k) is 99.9% gold content, but it is too soft for everyday jewelry. To increase durability and change the color, other metals are added to form an alloy, which reduces the percentage of pure gold.
For example, 18k gold is 18 parts gold and 6 parts other metals, meaning it is 75% pure gold. A 14k gold alloy contains 14 parts gold and 10 parts alloys, resulting in 58.3% purity. The non-gold percentage allows for the manipulation of color and grants the necessary hardness for daily wear. The amount of non-gold metal is the specific variable that enables the development of white gold’s unique coloring.
The Role of Alloying Metals in Color Change
The transformation of yellow gold into white gold begins with the addition of specific “bleaching” metals. These alloying metals are combined with pure gold to counteract its intense yellow pigment. The most common white metals used are palladium and nickel, sometimes supplemented with zinc or silver.
Nickel alloys create a hard and strong material, suitable for prongs and rings, while gold-palladium alloys are softer and more pliable. These white metals dilute and neutralize the yellow color, but they do not produce a true white. The resulting alloy is typically a pale yellow, grayish, or slightly tinted off-white color.
Manufacturers must balance the alloy mixture to achieve the best combination of color neutralization, durability, and workability. For instance, in 18k white gold, the 25% of other metals must be selected to bleach the 75% pure gold content. Despite efforts to neutralize the color, the inherent yellowness of gold means the alloy alone is not the brilliant white consumers expect.
Achieving the Brilliant White Finish: Rhodium Plating
The final, brilliant white color of white gold is achieved through rhodium plating. Rhodium is a rare, hard, naturally white metal belonging to the platinum group. It is applied to the jewelry surface using an electrical current in a technique known as electroplating.
This ultra-thin layer of rhodium serves two primary purposes. It completely masks the underlying pale yellow or grayish hue of the gold alloy, giving the piece a desirable mirror-like finish. The plating also adds a layer of protection, increasing the jewelry’s resistance to minor scratches and tarnish.
Why White Gold Requires Periodic Maintenance
The rhodium plating that provides the bright finish is not a permanent layer. This coating is microscopically thin, often measuring less than one micron in thickness.
Over time, the plating gradually wears down due to friction, chemical exposure, and daily use. Jewelry worn constantly, such as engagement rings, experiences the fastest wear, particularly on the bottom of the band or high-contact edges.
As the rhodium layer thins, the underlying, slightly yellowed or grayish white gold alloy begins to show through. To restore the jewelry’s original white appearance, professional re-plating, often called “rhodium dipping,” is required every one to three years.