ef·flo·resce / ˌefləˈres/ • v. 1. [intr.] (of a substance) lose moisture and turn to a fine powder upon exposure to air. ∎  (of salts) come to the surface of brickwork, rock, or other material and crystallize there. ∎  (of a surface) become covered with salt particles.2. reach an optimum stage of development; blossom: simple concepts that effloresce into testable conclusions.DERIVATIVES: ef·flo·res·cence / -ˈresəns/ n.ef·flo·res·cent adj.

effloresce burst forth as in flower; change to fine powder. XVIII. — L. efflōrēscere, f. EF- + flōrēscere (see FLORESCENCE).
So efflorescence XVII, efflorescent XIX.