What is White Gold?
White gold is an alloy of pure gold and one or more white metals. Commenly jewelers use palladium and nickel to mix with pure gold in order to make white gold. As you can see white gold is an alloy of pure gold and other white metals, so there is no "pure white gold". There are 18K white gold and 14K white gold according to the percentage pure gold the alloy contains. Pure gold is 24K gold, thus 18K white gold means it contains 75% gold and 25% other white metals. While 14K white gold means it contains 58.3% gold and 41.7% other white metals.
Since the original color of gold is yellow, in order to enhance the whiteness, almost all white gold is plated with rhodium. Rhodium is a white shiny metal which is especially hard. The rhodium can be worn off during years of wearing and revealing the original metal color. So usually white gold jewelry need to be re-plated with rhodium to restore the whiteness. Below is the composition alloy of 14K white gold and 18K white gold:
14K White Gold vs 18K White Gold
14K white gold contains 58.3% gold and 18K white gold contains 75% gold. Since gold is soft element, the less gold contained, the harder is the jewelry. So 14K gold is most recommened for jewelry, especially for gemstone jewelry. 14K white gold is resistant to scratches and more durable than the higher karat 18K white gold. For jewelry items for daily wear, like a wedding ring, charm bracelet, 14K gold can be a better choice than 18K gold. However, 18K gold also can be strong enough for daily wear with proper care.