Air bubbles collect and explode at the surface of many viscous liquids, as observed with polymer foams, in glass furnaces, and during volcanic eruptions, The liquid film separating the bubble from bulk air can have a long lifetime (if it is viscous) even if it is not protected by a surfactant, These "bare" films display unusual dynamic behaviors in drainage and rupture, Two different model systems were studied : a polymer melt (silicone oil) and a molten (borosilicate) glass of comparable viscosity, Although the two systems differ greatly in their relaxation time, they are described by the same set of laws, which can be understood from a relatively simple hydrodynamic model.