
Unlike ordinary dirt or grease marks, paint bonds very firmly to glass surfaces. Some paint-removing techniques -- metal scrapers or electric heat guns -- could damage the mirror's delicate surface, but the appropriate paint-stripping chemical will loosen the paint without damaging the mirror beneath. If the dried paint is simply errant drips and spatter from a recent painting project, ordinary nail polish can soften it up for easy removal. But when you're dealing with old dried-on paint, you'll need a more robust solution such as a paint-stripping paste.
Fresh Paint Spatter
Step 1

Slip on a pair of rubber or latex gloves.
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Step 2

Pour a generous amount of fingernail polish remover onto a small portion of a folded or wadded-up paper towel. Rub the wet paper towel onto the paint specks to soften them, then wipe the paint off the mirror.
Step 3

Soak a paper towel with vinegar, and use it to clean and polish your mirror.
Old, Dried-On Paint
Step 1

Slip on a pair of rubber or latex gloves.
Step 2

Open a tub or bucket of N-methyl pyrrolidone-based paint-stripping paste.
Step 3

Apply a thin layer of NMP-based paint stripper over the dried paint on your mirror, using a disposable brush. Allow the stripper two hours to soften the old paint.
Step 4

Slide a plastic putty knife under the NMP paste, and gently pull the paint and paste mixture away from the mirror. Repeat until all the paint has been removed.
Step 5

Soak a paper towel with vinegar, and use it to clean and polish your mirror.