Lexicon
Bloom
A fine, whitish crystalline film on long-aged cigars — harmless and a sign of maturation.
Bloom, also called plume, forms when oils migrate to the surface during long box ageing and crystallise there; the dusty film can be removed with a soft brush. The risk of confusion is with mould: mould is bluish-green, grows in patches, and adheres to the wrapper. When in doubt, the affected cigar should be discarded and the climate in the humidor checked.