The melting point for aluminum is only 1220F or 660C. A confined 500w lamp can generate that much easily. As someone pointed out, anyone who has left the doors on a Tota closed, the reflector doors become a heat trap and the inside melts. I've replaced more than my fair share when students have left them closed.
As for scrims, for the most part they are made out of steel because they have a tighter weave and therefore absorb more of the radiated heat. Steel typically melts in the 2500F or 1370C range...twice that of aluminum. Ironically, the protective screens on a Tota are made from aluminum. They have a wide open weave, and a ring around the outside. This ring helps to draw the heat away from the middle of the screen. Without that ring (other than giving it some structure), the screen would deform or even melt. Heat moves to areas of lower temperature in metal. The ring is behind the lamp, and is much cooler, so the heat radiates off of it. Just a little physics/chemistry lesson for you guys...
Rocky, it was probably a coating that began smoking on your screen, although depending on your wattage, how close to the lamp, and how focused the light was it could have been the bare aluminum begining to melt.
The scrims and protective screens aren't that expensive, and you will have perfectly sized, safe protection for your talent without having to "make it fit." I'm all for coming up with innovative cheap ideas to do things alternatively, but safety isn't something you should mess with. If you are doing it for effect, it is much easier to get a scrim that is exactly what you need. If you have time to tinker around with it, by all means go for it...Just remember the ring...
