White gold is an alloy of gold and some white metals such as silver and palladium. In Australia, the common alloys used are 18ct, 9ct, and sometimes 14ct. 18ct white gold is made by mixing 75% gold (750 parts per thousand) with 25% (250 parts per thousand) other metals such as silver and palladium.
In practical terms, 18ct generally holds up to everyday wear better than 9ct and tends to look better than 9ct as it ages over the years. This is one of the reasons why 18ct is normally preferred for ladies engagement rings rather than 9ct.
When white gold rings are new they are coated with another white metal called Rhodium. Rhodium is a metal very similar to platinum and shares many of the properties of platinum, including its white colour. Traditionally nickel was used in white gold; however, nickel is no longer used in most white gold made today as nickel can cause reactions with some people. We do not use nickel in our white gold.
The rhodium plating is used to make the white gold look whiter. The natural colour of white gold is actually a light grey shade. The Rhodium is very white and very hard, but it does wear away eventually. To keep a white gold ring looking its best it should be re-rhodium plated approximately each twelve to eighteen months, which is not an expensive process.