When is white gold not white gold?

When a consumer walks into a shop to buy an item of gold jewellery, if it is yellow or red then by checking the hallmark (if buying in the UK) they can tell at a glance, with the aid of a loupe, if it is 9K or 18K for example - the colour is fairly obvious. White gold is another story. Yes they can check the caratage just as easily, but what about the colour? Are they looking at the actual gold alloy or is a thin plating of Rhodium disguising the metal beneath?

First a few facts.

24 carat gold is yellow.

White gold is produced by adding a careful selection of white metals that bleach yellow gold. Strong bleaching metals are palladium, nickel and platinum. Moderate bleaching white metals are silver and zinc. This tends to historically produce two classes of white gold, nickel alloys and palladium alloys. Because of the price of palladium, the palladium whites are the most expensive and whiter alloys.

Many low grade commercial white gold alloys do not produce an acceptable level of whiteness to the consumer, therefore it has become common practice for manufacturers to rhodium plate items of jewellery to give the nice