Slip trailing
Slip trailing is the Anglo-American folk pottery default. A liquid clay slip (typically Albany or Bristol) is applied to the leather-hard pot through a fine nozzle, in lines, dots, and calligraphic gestures. The slip fires into the body and survives functional use. The Jugtown tradition of freehand slip-trailed decoration — "crawl," "loop," "splash" — is the most recognizable surface in the western NC folk style.
Decals
Ceramic decals are printed images on a water-soluble film, applied to the glazed and fired surface, then re-fired at low temperature to fuse into the glaze. Decals allow photographic and typographic imagery impossible by hand. In the High Country tradition, decals are used most often for the maker's mark. Underfired decals wear off; overfired decals burn out.
Luster
Luster is a metallic overglaze fired in a third, very-low-temperature firing (cone 018 or below). It contains precious-metal salts — gold, platinum, silver — in an oil and resin medium that burns off and leaves a metallic film. Luster is decorative, not functional. Potters reserve it for commemorative work.
Glaze chemistry, briefly
A glaze is a thin glass, melted onto the clay body in the kiln. Every glaze is built from three components: glass formers (silica), stabilizers (alumina, which keeps the glass from running), and fluxes (soda, potash, calcium, boron — the low-melting materials that let silica melt at kiln temperature). The Seger unity formula — RO:Al₂O₃:SiO₂ in molar ratios — is still how a glaze is designed on paper. The wood-fired ash glaze is the simplest: just wood ash, melted onto the pot by the kiln's own heat.