How long should a properly-stored emulsion remain stable?

• A. One year
• B. Two years
• C. Three years
• D. Five years

Answer: (C)

A properly-stored emulsion should remain stable for approximately three years. This timeframe is based on the chemical stability and integrity of the ingredients used in emulsions, which are mixtures of oil and water stabilized by emulsifying agents. Over time, emulsions can be susceptible to separation, microbial growth, and degradation, which reduces their effectiveness and safety.

The three-year stability period allows sufficient time for the product to maintain its intended consistency and efficacy under proper storage conditions, which typically involve keeping the product in a cool, dry place and ensuring it is tightly sealed to prevent contamination. While there are products with preservatives that can extend their shelf life, three years is a general guideline for many cosmetic emulsions that balance efficacy and safety.