I purchased a new bifocal mask, XS Scuba Gauge Reader. Does anyone know if it is safe to burn off the protective film without risk of damaging the bifocals? Is there a better/safer method? Never did it before, so I figure I should inquire before doing something wrong. And how can you tell you removed it completely? My current mask is the one I've used for snorkeling forever and never removed the coating. Didn't know it had one.