Re: Light bulb science and technology

[Chuck Britton <britton@odie.ncssm.edu>]

> At 17:44 3/15/98 -0400, Ludwik wrote:
> > How do they manufacture tungsten filaments which are double-coiled?
> > Was it always like this? I remember seeing single coils when I was a kid.
> > But it did not occur to me to look through a magnifying glass.
> They start with single-coiled wire!
>
> Or (one step back) with a thick wire extruded or swaged to size.


	Before tungsten can be swaged or extruded it must be saturated with
copper.
	After the extrusion and coiling process the copper is vaporised
from the
	filament, leaving the tungsten pure once again!
> Or ( two steps back) from a sintered tungsten powder bar, amalgamated
> with extended Joule heating in an inert atmosphere, then hot worked.
>
> Or (three steps back) from fine tungsten powder with a little thoria for
> sag-resistance.
>
> But let's get serious: begin with Wolframite or Scheelite....
>
> Whatcott    Altus OK


It's no accident that stressed		Chuck Britton
spelled backwards is desserts.		britton@odie.ncssm.edu