After your mug is completely bone dry, it is time to convert it from clay to ceramic in the bisque firing. Once bisqued, glaze it with food-safe glazes. The interior glaze should be glossy and the glaze on the rim should be thick enough to give a gently rounded, comfortable surface when the mug is used.
For my demo mug, I used a reddish brown gloss glaze on the interior and a thinly-applied transparent glaze on the exterior. The mug was fired to cone 7 in an oxidation atmosphere.