Glass blowing follows several stages demonstrated in the glassmaking hall of the Verrerie de Biot. First, the glassmaker picks a ball of molten glass from the crucible with his cane (picking) and rolls the glass on the marble to center it (marbling). He then introduces an air bubble into the glass by blowing at the other end of the cane and repeats the blowing operation after successive reheating until reaching the final volume of necessary hollow glass. In case of open-air blowing (photo), the master glassmaker varies the positions of the cane and maintains a constant and regular rotational movement.