Clean a bathroom mirror without soaking its edges: spray the cloth, then dry
Use a soft cloth lightly moistened with water or a mirror-approved cleaner, and dry the surface and edges promptly. Avoid flooding seams and the mirror backing.
IKEA instructs owners of its bathroom mirrors to wipe glass using a cloth dampened with water or a window cleaner, then dry it. Applying liquid to the cloth rather than the glass also helps avoid wetting edges and joins.