Abstract: A method of manufacturing a sheet of glass comprises: (a) forming a vertically oriented ribbon of glass that moves downward as a function of time, the ribbon of glass having a first primary surface and a second primary surface that face in generally opposite directions and a core disposed between the first and second primary surfaces; (b) as the ribbon of glass moves downward, passing the ribbon of glass adjacent to a first raised temperature zone liquefies the first primary surface while a temperature of the core remains below a softening temperature; and (c) after the ribbon of glass moves below the first raised temperature zone, separating a sheet of glass from the ribbon of glass. Passing the ribbon of glass adjacent the first raised temperature zone reduces total thickness variation, surface roughness, and other surface defects of the ribbon of glass.