Diglyercol tetranitrate is an energetic nitrate ester plasticizer having no freezing point, making the nitrate ester plasticizer especially suited for use in solid rocket motor propellants that are subjected to low temperature storage and operational environments, which can reach as low as -54°C in temperature. In order to avoid problems associated with fume-off that characterize the conventional synthesis method of making diglycerol tetranitrate, synthesis is performed in a medium including a mixed acid phase and an inert organic phase. The mixed acid phase contains, as ingredients, at least one nitronium ion source and at least one acid having sufficient strength to generate nitronium ions from the nitronium ion source. The nitronium ions in the mixed acid nitrated diglycerol to form diglycerol tetranitrate, which is then received into the organic liquid. The organic liquid, which preferably is a chlorocarbon such as dichloromethane, is insoluble with diglycerol but soluble with diglycerol tetranitrate. The inert organic phase is then treated to neutralize any acid contained in the inert organic phase, and the diglycerol tetranitrate is separated from the inert organic phase.