Need a suggestion on how to remove a bathroom mirror that was installed on the wall using a mastic adhesive and it was put there to stay forever.
Need more info. what type of wall is it fastened to? Do you want to save the mirror and how much trouble are you willing to go to? Is it framed? There are several options depending on the circumstances.
You might try, very carefully, using a heat gun to loosen the grip of the adhesive and applying very light pressure to separate the mirror from the wall behind it. Be sure not to concentrate the heat in any one area and wear gloves and goggles to protect you from anything that might happen. Just my two cents...