Ways to repair spots on bathroom mirrors include resilvering the mirrors and using frames to hide the spots. You need liquid lead, mirror stripping, stained glass paint or decorative glass beads to frame the damage. A razor scraper, a face mask, mirror of the same size as the old mirror and chemical silver remover are handy for resilvering the mirrors. You can buy some of the materials from a local home improvement store.
If the spots are along the edge of the mirror, attach a mirror stripping along the edge, and frame the mirror. Alternatively, use adhesive to attach glass beads or tiles over the spots, or remove the mirror from the wall, lay it on a flat surface, and use liquid lead and stained glass paint to decorate around the mirror.
Resilvering is necessary if the spots are severe. First check the mirror to ascertain the material it is made of. If it has harmful substances, such as mercury, seek the services of a professional to remove the backing, or wear appropriate protective gear before starting the repair. Remove the mirror from the wall, and place it face down on a flat surface.
Scrape away the silver backing with a razor scraper or special chemical remover, and discard the removed material properly. Attach a new mirror over the old mirror with glue. Replace the mirror to its original position.