Preburning or "baking":
Paint, sealants and glue that are going to be used inside a headlight assembly must be preburned before assembling. During preburning, the temperature must at least reach the maximum a headlight will see during a extremely hot summer day, with all lights on and cooking hot engine. A typical item that needs preburning is optical shields or shrouds. Use an oven and set it to ~280F (~150C), without exceeding maximum temperature according to the paint, the sealant or the glues. First heat oven to desired temperature, then turn overn off. Wait 2-3 minutes for the elements to turn from red hot to black. A typical preburn time is 20-30 minutes. Because oven is off, uou may have to do a second round by repeating the procedure. In general, this applies to all kinds of glue, paint and sealants. If this is not done properly, fumes will fog up lenses and reflectors. It is not recommended to have this happening to your headlights. The only liquid that will attack condensed fumes are 90% rubbing alchohol or paint thinner. Many surfaces cannot take such harsh fluid. Reflectors is the worst. It can be difficult or impossible. You may actually find that it also removes reflective material.