n A device inserted into a mold force, cavity, or core that delivers Bubble Tube Viscometern One of the bubble viscometers which is used by comparing the speed of a rising air bubble in a liquid of unknown viscosity with that of a liquid of known viscosity, both liquids being in corked glass tubes of identical size, and at the same temperature. Syn: Air Bubble Viscometer. (Patton TC (1979) Paint flow and pigment dispersion: a rheological approach to coating and ink technology. Wiley, New York; Paint and coating testing manual (Gardner-Sward Handbook) (1995) MNL 17, 14th edn. ASTM, Conshohocken).