18k gold refers to gold that is alloyed with other metals to create a mixture that is 75% pure gold. The "k" stands for karats, which is a measure of the purity of gold. In an 18k gold alloy, 75% of the material is pure gold, and the remaining 25% is composed of other metals. The purpose of adding other metals is to enhance the durability, strength, and color of the gold.
The specific composition of the alloy depends on the type of metal added. Commonly used alloying metals include copper, silver, nickel, and zinc. The choice of alloys can also influence the color of the gold. For example, white gold is often made by alloying gold with metals such as nickel, palladium, or silver.
Compared to higher karat gold (e.g., 24k), 18k gold is less soft and more suitable for crafting durable jewelry. It strikes a balance between the warm, rich color of pure gold and the practicality of added alloys. 18k gold is widely used in the creation of various types of jewelry, including rings, necklaces, bracelets, and earrings.