Gold of different colours has been used in jewellery ever since man discovered smelting. The use of coloured gold reached its golden age (no pun intended) in the 18th century, when master goldsmiths produced beautiful and elegant boxes containing up to 5 hues of the metal. It was an art only equalled by Fabergé in Russia. However, in the last few years a strong demand for golds of different colours in jewellery has prevailed, especially rose gold. And Cartier’s Trinity collection, featuring pieces in rose, yellow and white gold continues to be one of their classic bestsellers. One of the most frequently asked questions in my trade is ‘What is the difference between rose, white and yellow gold? Are they natural colours?’
The answer is fairly simple: all gold when it comes out of the ground is a rich, yellow colour. Pure gold- or 24 carat gold- is too soft for jewellery purposes and needs to be alloyed with other metals to give it the necessary durability for day to day wear. The carat number it is given refers to the parts of pure gold the alloy contains- so 18 carat gold (the most commonly used alloy in jewellery) is 18 parts pure gold, 6 parts alloy.
The type of alloy smelted into the gold will determine its distinctive colour. Plain 18 carat yellow gold is alloyed with copper and silver. Pure gold is reddish yellow in colour, the alloyed version being the creamy, warm yellow so familiar to us. Rose- or red- gold contains a much higher proportion of copper- the more copper, the more intense the colour. White gold is achieved with the addition of a silver-palladium alloy or nickel-copper-zinc. White gold is really cream in colour and requires rhodium plating to achieve the brilliant white finish familiar to us. Platinum and white gold are not the same thing at all- they are completely different metals and require different techniques in jewellery making. Platinum is much tougher and is naturally brilliant white, requiring no plating.
Other colours also favoured by master goldsmiths are green and blue- although these are now very rarely seen. These colours are not in fact strong- they are greenish gold and bluish gold. Green is made by adding cadmium and blue by adding indium.
Black gold has also been rising in popularity- it looks marvellous with black diamonds and gives coloured stones, especially greens and reds a luminous quality. However, this is not an alloy but a surface treatment and buyers will need to get their pieces replated if they scratch the surface finish.