Crackle and Salt MugsApproximately 4" Tall Bozeman native, Kirk Belding throws some beautiful pots! Unique glazes through a salt firing process produces some incredible color variations in Kirk's pieces. Salt firing is a vapor glazing process where salt (sodium chloride) is introduced into kiln firebox at high temperature. The salt vaporizes, and sodium vapor combines with silica in clay surface, forming extremely hard sodium silicate glaze.