A laboratory device, in particular a rotary evaporator, serves for evaporating a substance, preferably under reduced pressure, and comprises an evaporation flask for receiving the substance to be evaporated, a condenser for condensing the evaporated substance and a vapor passage for passing through the evaporated substance, which vapor passage is arranged in a vapor path between the evaporation flask and the condenser. The laboratory device further comprises a detection unit for foam detection, which detection unit is provided outside of the vapor passage and/or the evaporation flask.