For water-in-oil emulsions, a lower HLB value is typically suitable.

• A. True
• B. False
• C. Not applicable
• D. Depends on the emulsifier

Answer: (A)

Water-in-oil emulsions are stabilized best by surfactants that are more lipophilic, which means they have a low hydrophilic-lipophilic balance. The HLB value indicates whether a surfactant is more hydrophilic or lipophilic: low numbers are oil-loving and favor stabilizing water droplets dispersed in oil, while high numbers are water-loving and favor oil droplets dispersed in water. So, for W/O systems, a lower HLB is typically suitable to create and maintain the dispersed water droplets within the oil phase. In practice, emulsifiers around the low end of the HLB scale (often with blends to hit a specific effective HLB) are commonly used for W/O formulations. If a high-HLB emulsifier were used, it would more likely produce an oil-in-water emulsion. This is why the statement is true.