Hi Bob, many of those 3-light fittings are NOT suitable
for larger bulbs. The socket itself might be ok but
the fitting won't take the total watts heat.

My 3-light kitchen fitting gets over 85 degrees C (yes
I have a infrared thermometer) with 60w bulbs in it.

When your bulb goes on/off intermittantly the filament
has failed. Broken filament. You're relying on luck
to make it connect. :o) Also, the symptom of the bulb
separating glass from the metal cap is a sure symptom
of excessive heat, fatiguing the solder that holds them
together. I guess your kitchen lights are on a lot,
and it gets hotter in there than other rooms, and you
have 3 larger bulbs as kitchens need a lot of light.

Try 2 compact fluoros in there, will reduce the heat
to almost nothing, and give good light. My kitchen
now has them. :o)

I also suggest checking the temperature of your home
light fittings, you might be surprised how dangerous
they are, most wiring cables are rated at 85'C and
my lights were at that temperature or higher...
-Roman


Robert E. Griffith wrote:
>
> Thanks for the suggestions.  Here are some facts:
>
> * The bulbs are incandescent, not halogens.
> * The fixture is hanging from the ceiling, 3 bulbs, each with a metal
> reflector above it - looks like plenty of ventilation to me.
> * Each socket is rated for 100w.
> * All three bulbs that separated were 60w.
> * We have used 60w and 100w bulbs - failure rate is about the same.
> * The mysterious off again / on again bulb is 100w.
> * Thermal shutoff cannot explain mysterious bulb because it will not light
> even when fixture has not been used for hours and I measured the voltage in
> its socket while it was not working.

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