Surfactants sometimes produce emulsions that are unstable, so a secondary emulsifier/stabilizer can be added to the emulsion.

• A. False
• B. Not Sure
• C. True
• D. Sometimes

Answer: (C)

Surfactants lower interfacial tension and form a film around droplets, which helps stabilize an emulsion, but that film isn’t always enough to prevent instability. When droplets coalesce, cream, or drift due to insufficient film strength, adding a secondary emulsifier or stabilizer can significantly improve stability. This can happen by creating a stronger or more robust interfacial layer (for example, using a second emulsifier with complementary properties), increasing the system’s viscosity to slow drainage and droplet movement, or providing steric/electrostatic barriers that keep droplets apart. In practice, formulators may blend emulsifiers with different HLBS, or add polymers or particles to bolster stability. So, it is true that a secondary emulsifier/stabilizer can be added to address instability in emulsions.