1. Problem: Caking — When a Free-Flowing Powder Becomes a Solid Block Calcium chloride (CaCl₂) and magnesium sulfate (MgSO₄) are among the most aggressively hygroscopic industrial chemicals, absorbing moisture from air at relative humidity as low as 15-20%. During sea freight, even minor moisture ingress through FIBC liners causes surface dissolution of salt particles, followed by re-crystallization during cooler night periods. This dissolution-recrystallization cycle creates