a little more on why..... based on theory, not sad enough to have done much experimental observation....
evaporation of the element materials...
when you heat something so it's that hot, some of the material is evaporated.... heat is basically highly agitated molecular movement, the hotter something gets, the eaiser it is for molecules to escape , whether it's a solid or a liquid, so, slowly, but surely, material leaves the element, and since the coolest thing in the bulb is the glass, it condenses on the glass, leaving a fine slivery deposit...
when a filament fails , it would seem a lot more does it at once, i'd surmise that as the filament breaks , so the arcing that happens as it begins to separate, vaporises fair bit more material quite rapidly, so the sudden "plating" of the inside of the glass.
of course, if any of this is wildly inaccurate i'd be happy to be corrected.....
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Topic: Why ? (Read 1107 times)