Laryngeal mirror is warmed before use by placing:
High-Yield Explanation
(a) Glass surface on flame(Ref. Dhingra, 6th ed., 384)Laryngeal mirror is warmed before use by placing the glass surface on flame to prevent fogging caused due to breathing.Putting back of mirror on flame or will heat its back surface also which when held against the soft palate of the patient, while doing I/L, will cause burn injury.