Here is the answer to the question based on the provided reference:
Blackening white gold can be achieved through oxidation, a technique involving applying an acid to the metal's surface.
One method for blackening gold, including white gold which typically has a karatage below 24K, is through a process called oxidation.
- The Process: This technique involves applying an acid to the gold's surface, causing it to oxidize and darken.
- Karatage Requirement: This method is effective because white gold is an alloy, meaning it's not pure 24K gold. As the reference states, "Because pure gold doesn't react with oxygen, oxidation requires a gold with karatage under 24 karat — meaning 22K, 18K, 14K, 12K, or 10K gold." Since white gold is commonly found in 18K, 14K, or 10K, it meets the necessary condition for oxidation to occur.
By applying an acid to the surface of a white gold item, the metal alloys within the gold (which are under 24K) react and oxidize, resulting in a darkened or black finish.
