White gold is a gold alloy. This means it is a mixture of gold and another metal, which is usually a white metal such as nickel, silver or palladium. The ideal white gold is made out of palladium and gold and is both hard and strong. Most white gold jewellery is only slightly white and is therefore covered with a rhodium coating to make it look bright white. The quality of white gold is given in carats.
Look on the white gold to determine the carat count. The carat count will normally be stamped on an inconspicuous part of the white gold, such as the inside rim of a ring or the back of a pair of earrings. 18-carat white gold is the most pure, but it is also the most soft and generally the most yellow of the white gold variety. 14-carat white gold is stronger than 18-carat white gold and will appear whiter. If your white gold is delicate and will not be worn often, the softer 14 to 16-carat white golds are recommended. If it is a ring you should look for 10 to 14-carat white gold, which will be stronger and whiter.
Determine if the white gold is rhodium plated by examining its colour. Rhodium plated white gold will have a brilliant silver colour, while uncoated white gold will appear slightly yellow or grey. If the white gold is rhodium plated, the rhodium will wear off and the item will need to be recoated. While most white gold today is rhodium plated, very high quality white gold is not, and it will appear slightly grey. Poor quality white gold will appear more yellow than higher quality white gold and will need to be recoated more often.
If you determine that the ring is rhodium coated, examine it to see through the coating to the colour underneath. This will help you determine what the item will look like when the coating wears thin in the areas where it touches the skin. High quality white gold, which is less yellow and more silver, will contrast less with the rhodium coating and will make it less noticeable when the coating wears. Poor quality white gold will show very yellow colour through the rhodium coating as it wears.
Avoid purchasing white gold that is mixed with nickel. The nickel will make the white gold softer, more vulnerable to scrapes and bangs and can cause an allergic reaction. In some cases, the nickel will cause a red rash where the white gold comes touches the skin. Ask the dealer if the white gold is nickel free.