The evaporated tungsten binds with the gas and later precipitates again on the hot filament The glass must closely surround the lamp for this process to take place. Advantages over the incandescent lamp are: - Higher efficiency. - Smaller installation space. - Longer service life - Higher light output. When fitting a halogen bulb, take care not to touch the bulb glass with your fingers or a greasy cloth.Skin oils and salts evaporate on the hot lens and condense on the reflector material of the headlamp. As a result, the lens and reflector become cloudy. This shortens the service life of the lamp and reduces the light output. Why should you not touch the glass lamp with your fingers or a greasy rag? The gas will escape from the lamp. The grease can bake onto the lamp, making the glass appear cloudy. The glass will break.