Abstract: The present invention provides a ring mold for shaping heat-softenable sheet material. The mold includes peripheral wall members enclosing a central cavity having an open upper end. The wall members have an upper sheet shaping surface with a peripheral shape and elevational contour that generally corresponds to a desired peripheral shape and elevational contour of a sheet to be shaped. A first set of slots are positioned along and extend through portions of one of the wall members and a second set of slots are positioned along and extend through portions of an opposing wall member. Each of the slots in the second set is generally horizontally aligned with a corresponding slot in the first set.

Abstract: A process of making cellulated glass beads by forming a mixture comprising glass particles and cellulating agent into nodules, heat treating the nodules to cause fusion of glass and evolution of gas from the cellulating agent to form cellulated glass beads, and cooling the cellulated glass beads to a rigid condition. The cellulating agent utilized has the characteristic of creating expansion forces due to the evolution of gas during heat treatment which are generated wholly or mainly while the glass viscosity is within the range 10.sup.6.5 to 10.sup.8.5 poises. The heat treatment is carried out with a quantity of cellulating agent at a maximum cellulation temperature which is not above the temperature corresponding with a glass viscosity of 10.sup.5.5 poises and for a time such that the beads immediately following the heat treatment are populated with cells, and after cooling have a bulk density of not more than 0.5 g/cm.sup.