Abstract: Silicate-based composition particles are rapidly and completely expanded to form an expanded, cellular particulate aggregate of maximum density in short periods of time at particle temperatures which are comparatively low, that is, 100.degree. C., compared to existing systems by the utilization of infrared heat sources, either gas or electric, to heat the silicate particles. The use of infrared energy operates in a surprisingly advantageous fashion when the expansion process is carried out on or in the presence of a surface having the capacity to act as a thermal mirror or absorber-reflector of the infrared radiation to make maximum utilization of the radiant energy by the creation of a radiation trap. Carbonaceous materials are preferred for producing such entrapment. A further significant aspect is the discovery of a time-radiation dependency.