Tungsten tools used in the glass-forming industry undergo complex damage process resulting from cyclic contact with molten glass and atmospheric air and from friction between glass and tungsten. The damage process involving oxide scale growth and wear has been studied on W rods of two different diameters, in contact or not with glass, with different friction velocities. Damage is characterized quantitatively and the contributions of oxidation, borosilicate glass–tungsten reaction, and wear are discussed.