The Leidenfrost Effect occurs when a liquid droplet contacts a surface far above its boiling point. The droplet instantly vaporizes at the contact surface, forming an insulating vapor cushion that supports the droplet and dramatically slows evaporation. The critical temperature is the
Leidenfrost point (~180°C for water). Below this, the droplet wets the surface and evaporates rapidly; above it, the droplet levitates and can persist for minutes.
Vapor pressure: P_v ∝ exp(-L/RT) | Lift: F = P_v · A | Lifetime ∝ (T - T_Leid)^(1/2)
The vapor layer thickness is typically 10–100 μm. The droplet oscillates due to vapor pressure fluctuations, and surface corrugations can cause it to "skate" across the hot surface.