Resulting glass foams can be described as a composite with a matrix consisting of glass and with reinforcing
particles consisting of the unreacted remaining part of the foaming agent(s). In fact, in that
process, only 20 to 30 % of the pre-introduced foaming agent react and are involved, by decomposition
and subsequent gas development, in the expansion process [2]. The unreacted part of the powder particles
(C, AlN, SiC) remains dispersed in the glassy walls of the cell material. For specific glass compositions
(lead glass), a reduction of the modifier cations occurs and leads to metallic droplets precipitation