During start-up, condensation which is normal, forms on the inside of the glass and causes lint, dust and other airborne partcles to cling to the glass surface. Also initial paint curing may deposit a slight film on the glass. It is therefore recommended that the glass be cleaned two or three times with a non-ammonia household cleaner and warm water (we recommend gas fireplace glass cleaner). The glass should be cleaned two or three times during each heating season.