Hi This doesn't look like oxide, it looks like tungsten crystals. these form as the filament evaporates and recondenses on the filament. This is part of why they fail. There are two factors. One is that they tend to thin over time by evaporation. The other is that they tend to get more brittle over time. It is rare to see one fail because of loss of vacuum but when it does, the filament turns to a whitish yellow powder. Most lights do not have a high vacuum. If they did, the glass would cover with evaporated tungsten quickly and bock the light. You might notice that only the tops of the bulb get darkened. This is because of simple convection of the gas in the bulb. Dwight _________________________________________________________________ News, entertainment and everything you care about at Live.com. Get it now! http://www.live.com/getstarted.aspx