Mechanism of surface depression on foam glass

The mechanism of the surface depression of the foam glass was studied. A method of powder sintering with plate glass as the raw material and carbon black as the foaming agent was adopted to investigate the influences of foaming temperature, soaking time, moisture content in the release agent, and flame preheating temperature on the surface depression of a foam glass blank. The results indicated that insufficient cooling rate and rapid foaming process that could not react synergistically with the surface tension and viscosity of the glass melt aroused the mismatching between the glass melt and the expansion or contraction of gas, resulting in upper surface depression of foam glass. Besides, the batch carbon black at high temperature reacted with residual water in advance to generate large amounts of gas and form the air space which could expand inside, leading to lower surface depression of foam glass.