The first difference between white gold and platinum is the most basic and is the foundation of all the other differences. White gold and platinum are different metals. White gold starts out as gold. Gold is yellow. Platinum is itself a white metal. White gold and platinum have their own properties that make them unique.
How is white gold made? White gold is an alloy of gold and some white metals such as silver, nickel or palladium. The white color is achieved by a careful choice of the alloying metals, which bleach the deep yellow of pure gold. The amount of alloy mixed with gold is called its karat. The key to understanding gold karat is the karat value over 24. An example is a 14-karat gold wedding ring. It is14/24, which equals 58.3% gold and 41.7% alloy. The white color is achieved by a careful choice of the alloying metals, which bleach the yellow of pure gold.
Platinum is a naturally white metal. It doses not need to be alloyed for color. Jewelry platinum is typically an alloy containing 90% to 95% platinum and the balance alloy. Iridium or ruthenium are used as a hardener alloy. Platinum is usually marked with .900 or .950 to mark its fineness. Some manufacturers state what alloy they are using like 90% platinum 10% iridium.
How white gold and platinum start out is one of the key differences. White gold even in the best mixture has a hint of yellow. Platinum is a gray white and will keep its color true. One big problem for white gold is the poor mixtures. Some manufactures of white gold look light yellow and never achieve the white look. It does not sound like a big problem because if you don’t like the light yellow look, of a specific manufacture then don’t buy it. New white gold rings are usually coated with a hard protective finish of rhodium, a silver-white metal like platinum. The rhodium plating is used to make the white gold look more white. The Rhodium is very white and very hard, but it does wear away eventually. When the rhodium wears away the quality of the white gold is seen for the first time.
Yes, you can recoat the white gold with rhodium every time it looks yellowish, but is that what you want. If you want a pure white ring, then platinum will keep it whiteness. If the light yellow look doesn’t bother you or it looks better to you then white gold is a great option.
Editorial note: the preceding two paragraphs were true at the time they were written, but recent technological advances have produced an alloy of white gold that is pure white, and does not need to be rhodium plated. This new alloy is called Star White Gold. It is still not widely available, so these paragraphs still apply to most jewelry, but Star White is different. Learn more...
White gold is an alloy of gold and some white metals...the white color is achieved by a careful choice of the alloying metals, which bleach the deep yellow of pure gold.
Alloying also effects the second issue. Both pure gold and pure platinum are soft metals. In fact both 24 karat gold and .999 platinum can be scratched and dented with a fingernail. Nether gold or platinum in their pure state will hold a shine for long. All white gold jewelry and most platinum jewelry are alloyed. The alloying is also a hardening process for both metals. The hardeners used in platinum is either 10% or 5% of the mix. 14 karat white gold has 42% and 18 karat has 25% alloy used to whiten and harden. The more alloy makes white gold a harder metal then alloyed platinum.
The hardness issue is important when considering the brightness of the finish. The harder the metal, the more shine the finish will show and hold. White gold is harder then platinum therefore it holds its shine longer. Platinum does not wear away. Like all precious metals, platinum scratches. However, the scratch on a platinum piece is merely a displacement of the metal and none of its volume is lost. Platinum achieves a satin finish and maintains it a lifetime.
Another minor difference is the weight. Platinum is heavier (specific gravity: 21.4) than gold (specific gravity: 19.3). When you alloy white gold the difference is even greater. The difference on a small ring is small but on a large piece, it is very noticeable. Both metals are price per gram, so this adds to the higher price of platinum.
Price is a big difference between platinum and white gold. Platinum cost 2.5 to 5 times more then white gold. Why? Platinum is a purer noble metal percentage in jewelry. Platinum costs about 2 time more in the market at this time (gold $425; platinum $880 per troy ounce). Platinum is harder to work with then white gold. The higher melting temperature makes it more difficult to cast. The platinum solders are also at higher temperature. These and other reason make platinum more expensive to work with then white gold. So the labor cost of platinum jewelry is more also.