Presented is a new gravity method for separating low-density plastics. Analogous to dense media separation, in this new low-density gravity separation process, instead of the suspension being water + high-density solids, it is water + law-density solids. Using water with suspended cork particles, one may create a medium with a density as low as 0.75 g/ml. Employing the same equipment as used for dense media separation, but with the low-density slurry, two or more materials with densities below 1 g/ml may be economically separated. One can separate the widely used commercial plastics PMP (0.83 g/ml) from HPDE (0.95 g/ml).