The raw materials are fine glass particles in pyroclastic deposits, which are pumice flow or vitric tuff deposits, and supplied into the furnace with air and LPG. The temperature of furnace is kept at about 1,000°C. Shirasu-balloons are collected by a cyclone.

Shirasu-balloons are utilized as fillers for various materials, such as plastics, Portland cement-based concrete, paper clay, putty, paint and so forth. Most of Shirasu-balloons are used as lightweight filler for building materials such as curtain walls for high-rise buildings. In addition, its unique characteristics are well utilized as filler for paper clay, filler for cos-metics, additives for explosives to increase the sensitivity and so forth.

Fig. Manufacturing process of Shirasu-balloons.