Abstract: Abrasive grains are removed from a glass substrate for a recording medium by washing with water containing an elevated amount of oxygen atoms. The oxygen atoms may be in the form of monatomic diatomic or triatomic molecules. In one embodiment, the oxygen is formed at the anode of an electrolysis apparatus. A small amount of an electrolyte may be used in the electrolysis apparatus without interfering with the ability to clean the glass substrate without generating latent flaws. The invention also is defined as a substrate cleaned by the disclosed method and a magnetic recording medium made from the substrate.