Abstract: In a VAD method for making optical fiber preforms, the yield is increased by terminating or significantly reducing the supply of glass raw material to the torch (24) just after glass jacket soot (23, FIG. 4) has been deposited at the bottom end of the glass rod (20). The fuel supply to the torch is maintained, however, and the flame continues to be projected from the torch toward the deposited soot boule (23). The rate of vertical movement of the glass rod is increased until the flame is directed at the bottom end (27') of the soot boule. The flame is then allowed to dwell for a sufficient period to increase significantly the temperature of the bottom end of the soot boule and to consolidate partially the bottom end of the soot boule. This has the effect of containing the soot and countering the effects of gravity on the delicate soot boule that might otherwise cause it to crack.