I just had a call from a contractor reporting an orange film forming on the inside of MR-16 bullet lenses with 50W lamps. I'm pretty sure the film was caused by out-gassing from the grease the contractor applied to the lamp pins. This led me to do a little research on greases used for this purpose (incl. reading the many posts on this topic here). One of the things that surprised me was the misuse of the term 'dielectric', and the fact that some contractors use dielectric (non-conductive) grease and others use conductive grease. Most expert opinion seems to discourage the use of non-conductive (dielectric) grease on socket contacts because it can interfere with the socket/pin connection - in fact, the connection can only be made because pushing the pin in the socket scrapes away the grease. Some claim that the resultant connection has more resistance than when there is no grease, and that this resistance can result in voltage drop and excess heat in the socket. It makes more sense to use conducting grease (if any) because this makes for a good contact and protects against corrosion. In fact, one popular grease used by our forum readers is the Sanchem No-Ox-ID "A Special" - a conductive grease (although many posts referred to it incorrectly as a dielectric grease). Getting back to my intial complaint (orange film residue) - the contractor didn't know what type of grease was used, but regardless of it being conductive or non-conductive, I'm guessing the 50W lamp pushed the heat past its specs. As you may know, CAST doesn't grease its sockets and doesn't recommend its use. We believe that our solid nickel pins mated to the solid nickel socket contacts are sufficient. Comments on the grease issue welcome.