Gold has been one of the most valued metals since time immemorial. In its pure form, gold is yellow and very soft. As one of the most common and popular use of gold is in the form of jewelry, it has to be made hard by adding other metals. In short, alloys of gold are used to make jewelry, though some people prefer the pure form. The purity of gold is measured in carats, and 24 carat gold is considered the purest. When other metals are added in different quantities, the purity level decreases to 22 (22 parts gold and 2 parts alloy), 18, and 14 carats.
Throughout the centuries, people loved to wear yellow gold only. So yellow gold alloys were used for making jewelry. The metals used for this purpose are copper and silver. While silver can make the gold greenish in color, copper can make it look more reddish. So, usually, a mix of copper and silver in the ratio of 50:50, is added to gold, so that the yellow color is retained. These metals, when added to gold, do not cause any noticeable color change. However, some people experimented with other metals to produce gold alloys in colors, like white, rose, gray, green, and black.
What is White Gold?
As mentioned above, gold alloys were initially meant for making gold more pliable, in order to produce fine jewelry. This was done by adding metals, like silver and copper, so that the traditional yellow color of gold is not altered. White gold alloys are made by mixing at least one white metal to gold. The commonly used white metals are silver, palladium, nickel, and zinc. White gold was introduced in the 1920s, as a replacement for platinum, which was very expensive and popular. Platinum supply became scarce at that time, and white gold was introduced. Since its inception, such gold jewelry became very popular and replaced platinum to some extent.
So, it is the proportion of the metals in the alloys, that changes the color of gold. The atomic structure of the gold alloy is different from that of pure gold. This atomic structure affects the reflectivity of light of different wavelengths, thereby changing the yellow color of gold to white. However, the original color of white gold may have light grayish or yellowish hue. So, white gold is given a rhodium plating, in order to obtain that white hue. It is rhodium, that gives that bright look and the reflective feature to white gold.
While nickel is one of the most popular metals used for making white gold, it can cause skin rash in people with sensitive skin. So, nickel is not considered healthy. It is also said that nickel has carcinogenic properties. So, palladium, platinum, and silver are mostly used for making white gold. However, people often complain of white gold turning yellow. How does it happen?
Why Does White Gold Turn Yellow
Now, we know that most of the white gold jewelry comes with a rhodium plating, which gives the white hue and reflective nature. Most people mistake these properties as that of white gold. Beneath the rhodium plating, lies the white gold alloy, which can be gray or yellowish gray. So, once the rhodium plating wears out, the color of the white gold alloy can be seen. This is the reason behind white gold turning yellow. So, with regular use, the rhodium plating in white gold jewelry wears out, exposing the inner alloy, which is not 'white'. Sometimes, yellow gold jewelry is plated with rhodium, and is sold as white gold. In such cases too, you may experience such color change. In short, white gold is not a metal in itself, as pure gold is yellow in color. White gold is actually gold alloys (mixed with white metals), that have the typical 'white' color due to the rhodium plating. As the plating fades with time, the inner alloy is exposed, and this is the reason for white gold turning yellow.
Essentially, the quality of rhodium plating is more important. Cheap ones can wear out soon, as compared to a good quality plating. Proper handling is also important, as rough usage can affect the plating. So, buy white gold from authentic and trusted jewelers, and handle it with care.