Upward collapse process and apparatus for making glass preforms

An apparatus for creating a glass preform from a glass body having a weight, a circumference, at least one free-standing stacked core rod, and a cladding surrounding the at least one core rod and being separated from the core rod by a gap, the apparatus comprising:

• a top collar affixed to the top of the cladding, the top collar having an outside diameter approximately the same as or smaller than the outside diameter of the cladding;
• a bottom collar affixed to the bottom of the cladding, the bottom collar having an outside diameter either smaller than or approximately the same as the outside diameter of the cladding;
• at least one spacer upon which the at least one core rod rests;
• a bottom collar holder and vacuum unit holding and supporting both the bottom collar and the at least one spacer, thereby supporting up to the entire weight of the glass body without contacting the outer surface of the glass body, the bottom collar holder and vacuum unit removing gas from or introducing gas to the apparatus;
• a top collar holder and vacuum unit holding and supporting the top collar, the top collar holder and vacuum unit removing gas from or introducing gas to the apparatus;
• and
• a frame defining a heating zone having a heating element to heat the glass body.