Thirteen samples of an efflorescence collected from the surface of beeswax seals or from beeswax used for their restoration were analysed in detail. The samples were of different origin, age and storage history. The composition and the incidence of the efflorescence was correlated with a chemical composition of historical and recent beeswax samples. The composition of the crystalline layer was found to be very similar in all the samples. Linear monounsaturated alkenes containing 31 and 33 carbon atoms, more precisely (Z)-hentriacont-10-ene and (Z)-tritriacont-10-ene, were identified as main components. The analyses of beeswax have revealed that all compounds identified in “wax bloom” naturally occur in recent beeswax. However, the historical beeswaxes contained only traces of unsaturated hydrocarbons, if anything. The efflorescence was observed primarily on the surfaces of those samples which contained larger proportion of alkenes. The presented results could be of particular importance not only for better understanding of the described phenomenon, but also for the development of new beeswax-based materials, which would be “bloom resistant” and useful for conservation purposes.