Old mylar on the playfield is lifting and dirty, and you want it off without pulling up the paint, for example before fitting a playfield protector.

Removing old peeling mylar: gentle heat or an inverted can of air

Cause: Aged mylar adhesive. Removal always carries some risk to the paint underneath, especially over cupped inserts.

Checks

• Try a small corner first and watch whether any paint lifts with the mylar.

Fix

• Warm a small area with a hair dryer or a heat gun on low, keep it moving, and peel slowly with tweezers or forceps.
• Or hold a can of compressed air upside down to freeze the mylar; it then lets go quickly (this method left more adhesive behind here).
• Remove leftover adhesive with naphtha and a plastic razor blade, stepping up to stronger solvents only if needed; never use acetone.

Systems

• Electro-mechanical

Games

• Grand Prix

Source: Pinball Repair help group!! (Facebook group)