Abstract: An effective abrasive composition is provided for polishing a plastic article, particularly a plastic lens, to give a mirror surface thereto. This abrasive composition comprises water, an aluminous abrasive and at least one polishing accelerator selected from the group consisting of aluminum oxalate and aluminum lactate, optionally with at least one sedimentation preventing agent selected from the group consisting of crystalline cellulose and colloidal alumnia.

Abstract: An abrasive composition comprising: an aluminous abrasive, preferably having an average particle size of 0.5-10 .mu.m and a concentration of 1 to 25% by weight; nickel sulfamate and/or sulfate, preferably having a concentration of 0.5 to 10% by weight; magnesium nitrate, preferably having a concentration of 0.1 to 12% by weight and water, the composition preferably having a pH of 4 to 7. This abrasive composition produces a superior effect, particularly a reduction of protrusions and pits and deep scratches when used for polishing an aluminum-based substrate for a magnetic recording disc.

Abstract: An abrasive composition particularly suitable for polishing an aluminum-based substrate for a magnetic recording disc, the composition comprising: an alumineous abrasive, preferably in an amount of 3 to 25% by weight; a polishing accelerator of gluconic and/or lactic acid, preferably in an amount of 0.1 to 3% by weight; optionally with sodium gluconate and/or sodium lactate in an amount of 0.1 to 3% by weight; colloidal alumina, preferably in an amount of 0.1 to 5% by weight; and water, the composition typically having a pH of 3 to 5.