A scratch on a mirror can destroy the mirror's illusion of depth and can also interfere with its purposes. Though it's not cost-effective to re-silver the back or grind the front of the mirror yourself, you can take steps to remove the scratches and repair the mirror. Read on to learn how to remove scratches from a mirror.
Remove the mirror from the wall or other hanging or holding surface. Lay it face down on top of a soft cloth to expose the silvering.
Spread some white toothpaste (not gel) onto the scratch and rub it in. Let it dry, then polish with a soft cloth. This makes the scratch less noticeable.
Mix a paste of dry mustard and white vinegar, using one part of each. Rub the paste into the scratch with a cloth, then buff with a dry, soft cloth. This is as effective as toothpaste, but some mirrors repair better with mustard paste.
Take the mirror to a professional to have it re-silvered if the scratch is too distracting. Most multipurpose glass shops do re-silvering, or you can ship your mirror to a specialty shop like Reflections Again. The entire mirror needs to be re-silvered for the best repair results.
Realize that re-silvering magnifies surface scratches and blemishes, especially in an old or antique mirror. In an antique, though, these blemishes give additional character.
Sand or buff out small surface scratches with a superfine polishing disc attached to a Dremel or similar tool, or polish by hand. Though this method can make scratches nearly invisible, it also creates distortion in the mirror. Decide whether surface perfection or mirror clarity is more important to you before taking this repair step.