A foam reduction agent consisting of dibasic esters is shown and a process using a liquid contact with polystyrene foam wherein the higher boiling temperature of the dibasic esters and contact with the liquid provides a volume reduction process and less evaporation loss as well as safer transportation of the chemicals and the polystyrene in its reduced state. The resulting reduced sludge is also recyclable to superior quality raw polystyrene foam beads and the reduction agents are recoverable for future use. The resulting sludge also has unexpected beneficial uses hereto for unknown as a waterproofing agent.