There were just too many similar elements in Mr. Chihuly's "Flori" series for individually-blown glass to be an economically justifiable option. Instead this outer mold was used, which through the use of inserts made of the same ceramic composition as was chosen for the Space Shuttle's reentry heat shield, allowed unique pieces with the same basic shape to be made very quickly out of molten glass.
Ok, that's not true: I'm no longer in the Dale Chihuly Garden and Glass Museum, and am now in the nearby Experience Music Project. This is one of the on-stage cannon used in AC/DC's 1981 "For Those About to Rock" world tour.
Related YouTube Video: http://www.youtube.com/watch?v=trVcO02nwAE