We found some papers with new recipes to foam glass. The first paper was written at the Iran University of Science and Technology in Teheran, which seems also to step into cellular glass.  Hereunder, you will find the abstract:

Foam glasses are encountered as one of the most promising solutions for waste glasses recycling issues. Homogeneous pores distribution and high mechanical strength are two main characteristics of these products which many investigations have been done for their optimization. High flexural strength glass foams were fabricated by usage of oxidant agents like Fe2O3 and Co3O4 besides soda lime glass wastes and SiC as a
foaming agent. Glass foams containing 4 wt % SiC and foamed at 850°C for 1 h had 90% porosity and bending strength of 0.75 MPa. Bending strength of specimens using increased to 6.82 MPa and porosity was decreased to 80% by addition of 1.2 wt % Co3O4. Moreover, the effects of Fe2O3 and Co3O4 on porosity, microstructure and mechanical properties of foam glasses were studied. Based on the results, the finest porosities with the highest size distribution homogeneity were observed in foam glasses contained Fe2O3 and Co3O4. Furthermore, Co3O4 addition produced slightly narrower pores size distribution in comparison with Fe2O3.

The same university also did some foaming of Cathode Ray Tube glass from old televisons. This is given in the following paper with abstract:

In the present study, the effect of temperature and oxidising agents such as Fe2O3 and Co3O4 on physical and mechanical properties of glass foam is investigated. The glass foam is made of panel glass from dismantled cathode ray tubes and SiC as a foaming agent. In the process, powdered waste glass (mean particle size below 63 mm) in addition to 4 wt-% SiC powder (mean particle size below 45 mm) are combined with Fe2O3 and Co3O4 (0?4, 0?8 and 1?2 wt-%) have been sintered at 950 and 1050uC. The glass foamed containing 1?2 wt-% Co3O4 has good physical properties, with porosity more than 80% and bending strength more than 1?57¡0?12 MPa. However, by adding different amounts of Fe2O3 in comparison with samples without iron oxide, little changes in porosity and strength are obtained.

Another paper  was written in Turkey at the Izmir Institute of Technology with abstract:

The foaming behavior of a powder residue/waste of a soda-lime window glass polishing facility was investigated at the temperatures between 700 and 950 C. The results showed that the foaming of the glass powders tarted at a characteristic temperature between 670
and 680 C.  The maximum volume expansions of the glass powder and the density of the foams varied between 600% and 750% and 0.206 and 0.378 gcm3, respectively. The expansion of the studied glass powder residue resulted from the decomposition of the organic compounds on the surface of the glass powder particles, derived from an oil-based coolant used in the polishing. The collapse stress of the foams ranged between 1 and 4MP aand the thermal conductivity between 0.048 and 0.079WK1 m1. Both the collapse stress and thermal conductivity increased with increasing the foam density. The foams showed the characteristics of the compression deformation of the open cell brittle foams, which was attributed to the relatively thick cell edges.

In the last paper, the foaming agent is the coolant used for the polishing of the glass. That is an interesting observation.