When does 18k gold embraced jewelry tarnish?

18k gold jewelry typically tarnishes less than lower karat gold due to its higher gold content, but it can still tarnish over time. This is often caused by exposure to moisture, chemicals, or certain skin types. Additionally, the alloy metals used in 18k gold, such as copper or silver, can oxidize and lead to tarnishing. Regular cleaning and proper storage can help minimize tarnishing.