Gold is naturally yellow in color; however other colors can be created by alloying gold with different metals. You can also “mask” the natural color by adding metals that have a “whitening” effect on the gold color, thereby giving you white gold. White gold alloys were developed in the 1920’s as an alternative to platinum, which was a much more expensive metal. The most successful white golds contain nickel or palladium, each of which have a strong whitening effect. As you can see in the alloy triangle below, silver can be used to produce a whitening effect, however only in very low karatages that are not desirable and do not give good mechanical properties for working the metal into jewelry. You usually don’t see white gold above 18k because will not be enough of the white metal present to overcome the natural yellow color of the gold. Remember that 18k gold is 75% pure gold.
Nickel white gold is made by alloying gold with nickel, copper and a small amount of zinc. The zinc is added to help stabilize the copper which is a very reactive metal and can cause tarnishing. Because of the reactivity of the alloying metals, white gold is often plated with rhodium, a naturally white platinum group metal, in order to improve the white appearance and protect the skin. The plating must be reapplied over time as it will wear off depending on the use and care of the jewelry item as well as the body chemistry of the wearer. Nickel adds a high degree of springiness to the gold, so it’s a great addition for bracelet clasps or hinge pins. Nickel has its problems however as it can cause allergic reactions in 10-15% of the population. In fact, use of nickel in jewelry is severely restricted in the EU.
Palladium white gold alloys are mostly gold, silver and palladium. Palladium is a platinum group metal, and these tend to be more of a greyish-white vs the bright white that is obtained by using a nickel white gold alloy and rhodium plating. Palladium white gold is not intended to need rhodium plating, although that also comes down to personal preference. Palladium white gold alloys are usually more expensive than nickel white gold, so the prices of jewelry using palladium alloys will reflect that. As I’ve mentioned before on this blog, alloy composition is often proprietary and the information mentioned here is only to be used as a guide. Alloy suppliers have been working to refine nickel white gold alloy recipes to reduce the allergic reactions that consumers can experience wearing white gold. A lot of this is because the United States really seems to prefer the bright white look that comes from the combination of nickel white gold and rhodium plating. For those consumers that are interested in sustainability and want to make a more mindful jewelry purchase, there are environmental effects to also consider when purchasing nickel white gold. Adrienne Krieger, owner of Everling Jewelry shared a journal post with contributions from an experienced environmental engineer which gives insight into the impacts that nickel mining has on the environment. You can read that post here. Another point to consider when deciding which metal may be right for you. If you would like to learn more about precious metals and their physical and chemical properties, a great reference book is Introduction to Precious Metals by Mark Grimwade. As always, please contact us with any questions and please subscribe below to be notified of new blog posts.
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