Fireplace glass is designed to be resistant to damage, as it needs to be thick enough to withstand the heat given off by a fireplace fire. The glass needs to be cleaned frequently to keep it looking its best because ash and fumes form stains that discolor the glass over time. While those substances wipe away with the help of glass cleaners, burned plastic requires special care, as removing it incorrectly often results in scratching of the glass surface. Burned plastic molds itself to the glass, which makes its removal more challenging.
Place a scraper against the base of the plastic if there is a larger piece melted on the glass. Keep the scraper as parallel to the surface of the glass as possible.
Press the scraper gently against the base of the plastic to wedge the edge under the melted plastic. This should pop off the majority of the plastic, leaving some residue remaining.
Spray the remaining plastic with an ammonia-based glass cleaner or acetate. Allow it to soak into the plastic for several minutes. Wear rubber gloves when using acetate.
Wipe the plastic carefully with a melamine foam pad. Start slowly and carefully, and then gradually add pressure to remove the plastic without scratching the glass. Melamine is very useful for stain removal but is abrasive when too much pressure is used.
Spray the glass with white vinegar. Wipe away any remaining stains or residue from the plastic with a microfiber cloth. The vinegar helps remove any remaining traces of the ammonia and helps clear the glass of remaining plastic residue as well.