Polymers can be dissolved in certain liquids, so called solvents, and do not dissolve in others. This can be exploited to remove colorants and other additives from plastic. The polymer is first dissolved allowing additives to be filtered out. After filtration, the polymer can be recovered either by vaporizing the solvent or by employing an anti-solvent. An anti-solvent is a liquid that does not dissolve the polymer. Its addition leads to precipitation of the polymer as a solid material, which can be recovered by filtration.