The glaze on this jug, is by some called Volcanic Glaze, which is a type of glaze where the proper use of certain ingredients can cause controlled (somewhat) gaseous explosions in the glaze, producing holes of different types. One of the best known creators of volcanic glazes is Otto Natzler, who fled to US from Austria in 1938, but it was only in the early 1960’s that volcanic glaze and the fat lava glaze became popular. Both West Germany pottery and the potters in French Vallauris embraced this unpredictable glaze, that fitted very well into the freeform and experimental new wave in ceramics around that time.