Which formulation is most likely to clump if stored in a humid place?

• A. EC
• B. SC
• C. F
• D. WP

Answer: (D)

Moisture affects dry powders most directly, and clumping occurs when tiny particles absorb water and stick together. A wettable powder is a dry solid formulation that must be wetted in water to form a suspension. In a humid environment, those powder particles readily absorb moisture, creating liquid bridges between particles that cause them to stick together and form a cake. The other formulations are liquids or already suspensions, so humidity doesn’t cause the same kind of particle-to-particle sticking. Emulsifiable concentrates are liquid blends, flowables are suspensions in liquid, and suspension concentrates are fine solids dispersed in liquid; while they can be affected by moisture, they’re less prone to the kind of caking seen with dry powders.