🚀 go-pugleaf

In article <1147@inews.intel.com>, bhoughto@cmdnfs.intel.com (Blair P.
Houghton) writes:
|> >Also, the quartz envelope shouldn't be touched by bare 
|> >hands -- oils on the skin will weaken the structure and may
|> >cause bubbles or lamp failure.
|> 
|> The oil causes a region of different thermal conductivity;
|> when the heat is applied this will cause a region of
|> different temperature which will cause a difference in
|> expansion which will cause a stress that will rupture the
|> envelope.  The oil doesn't "weaken the structure."  You can
|> wipe it off.

I don't think that's quite right. Quartz is used precisely because of
its
very low temperature expansion coefficient.

I think the problem is that the heat will decompose the oil, producing
elemental carbon which will then absorb the light hitting it from the
filament.  This causes a hot spot on the surface of the envelope which
could well cause it to soften and fail.

Phil