This is a question I am asked almost everyday. Particularly since today the white metals are very popular. No only has white gold become the metal of choice for the younger generation, but there has been a resurgence in platinum and silver. Palladium jewelery has become relatively common too. I am even seeing esoteric blends such as P4 a patented alloy, which is consists of silver, palladium, gold and platinum. Without question though, white gold is the metal asked for the most. But why does it yellow after a while?
All gold when mined is yellow. There is no naturally occurring “white gold”. Gold after refining is 24K or pure gold which is a orange-yellow metal. In this country jewelry manufacturers do not use pure gold but “alloy” or mix it with other metals. This process changes the purity of the metal, thus 14K (the most common fineness used in the U.S.) is 14 parts gold and 10 parts of alloy. It is the alloy that gives gold jewelry the color you see. White gold has an alloy mixture that contains nickel and other metals. More nickel in the mix, the whiter the gold will appear. Conversely the higher the gold content (for example 18K) the more yellow, white gold will appear. Gold jewelery is available in several different colors, white (with nickel alloy), yellow (with brass alloy), rose (with copper alloy) and green (with silver alloy).
Different manufacturers will alloy gold with different blends of other metals. There is no hard and fast rule as to the exact mix of materials that can be used. This is done for various reasons, strength, wearability, malleableness, or appearance. It is now common to alloy gold to be able to cast metal directly around stones held in a mold so that there is no labor to set them unfortunately resulting in a more yellow tinted white gold.
Nickel is also a “heavy metal”. It is really one of the very few true heavy metals used in jewelry. Besides other properties, a heavy metal is a metal that is poisonous in its natural state. Because the alloys of gold commonly used in the jewelry industry are mixtures and not compounds the individual metals retain their inherent properties. Some people may have a skin irritation from wearing white gold. I’ve seen a mild rash to a very bad case of excema. Many manufacturers are therefore using less nickel and more brass in their white gold resulting in a more yellow looking metal.
It is standard practice to “rhodium” plate white gold jewelry after the manufacturing process to make the item appear much whiter. Unfortunately when a piece of jewelry is re-worked, such as during a ring sizing or chain soldering the rhodium may be removed during the heating process or the polishing afterward, thus showing the actual color of the particular white gold the manufacturer used in the production of your item. Simply wearing your white gold jewelry will make it look yellow over time by removing the rhodium plating. The patina that is acquired over time is simply the surface being scratched and worn away atom by atom.
Additionally, many chemicals we all normally come in contact with each and every day will react with the various metals in the alloys causing white gold to look more yellow. Many of these chemicals are quite benign such as hard water, salts, soaps, hair dyes and makeup. Other chemicals such as bromine and chorine (used in pools, hot tubs, or in the laundry) actually break down the nickel in white gold and can cause failure or weakness resulting in broken prongs, lost stones, cracks or pitting.
Unfortunately because of the volatility and high price of rhodium not all repair persons re-rhodium jewelry items after repair. For example in June of 2008 rhodium hit an all time high of $10,010 per Troy ounce! But by November of that same year it had dropped to $760 per ounce. Currently it is at $2330. This volatility is attributed to supply and demand, political instability at some of the sources, and complexity in refining.
The simple solution is to refinish your item and re-rhodium the white gold. This is a process you may need to have done regularly depending on your individual life style. First, the item must be completely refinished to a high luster, and throughly cleaned especially removing any oily residues. The item can then be electroplated in a bath of rhodium salts. Any charges involved in this process are reflected by the high cost of rhodium and the time required to clean and polish your item.