sin, One think I have to add is this....having been working with these bulbs since the late nineteen seventies on motercycles, the fact is most people will touch the glass in one way or another before the install....or they could have been compremised by dirt or anything else that would cause the extra heat build up before you get them. What I always do when instaling a halogen bulb, is to just wipe off the all of glass area with a cotten ball and rubbing alcohol, then let them dry for a few seconds. This system has never failed to remove any unseen(or seen) crud on new (or used) halogen bulbs.