How gold is gold?
Getting technical... alloys which are mixed 14 parts gold to 10 parts alloy create 14-karat gold, 18 parts gold to 6 parts alloy creates 18 karat, and so on. This is often expressed as the result of the ratio, i.e.: 14/24 equals 0.585 and 18/24 is 0.750.
The more gold in the alloy, the more yellowish it will appear in color. The karat grade will always indicate the amount of gold in the alloy. For example, 18K = 75% pure gold. So for 18K, this only leaves 25% of the alloy for other metals to make it whiter. This is why 18K white gold is more yellowish than 14K white gold.