A new failure mode! 75w bulb

First time I've seen this one:

I come back from the kitchen, and my reading lamp (spring-clamp lamp) is glowing dull orange.

Turn off the switch. Switch feels fine (not burned.) LAMP DOESN'T SHUT OFF! OK, so maybe the switch is fried.

Unplug the lamp. LAMP DOESN'T SHUT OFF! I have the power cord in my hand.

So, I guess the switch was OK after all?

Over about 15 seconds the orange glow fades to dark. Unscrew the bulb. It's hot, but not unusually so. It does operate base-upwards in the lamp.

Examine the inside of the lamp with laser-pointer shadow. The filament is fine, unbroken. But the glass support for the iron wires has a large hole melted in the side.

So, it was still an incandescent lamp, but it randomly decided to use liquid glass as it's light-generator? Rats, I should have plugged it back in to see how long it could continue that way.

((((((((((((((((((((((( ( ( (o) ) ) ))))))))))))))))))))))) William J. Beaty Research Engineer beaty a chem washington edu UW Chem Dept, Bagley Hall RM74 billb a eskimo com Box 351700, Seattle, WA 98195-1700 ph 3-6195

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Reply to
Bill Beaty
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You had a Nernst.

NT

Reply to
tabbypurr

or, you have a lot of RF near by

Jamie

Reply to
M Philbrook

I have wanted to try heating up a fragment of ferrite rod as a Nernst lamp but I have no yard to safely test the idea.

Reply to
sean.c4s.vn

Yes, hot glass conducts ionically. I did some work once in a glass fibre factory which had a large (20T IIRC) tank of permanently molten glass feeding the extruders on the floor below. This was heated using oil, gas, or electricity, depending on the cost at the time. The electric heating just comprised electrodes fed from a suitable transformer.

Cheers

--
Syd
Reply to
Syd Rumpo

is glowing dull orange.

HUT OFF! OK, so maybe the switch is fried.

hand.

. It's hot, but not unusually so. It does operate base-upwards in the la mp.

t is fine, unbroken. But the glass support for the iron wires has a large hole melted in the side.

liquid glass as it's light-generator? Rats, I should have plugged it back in to see how long it could continue that way.

r.

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Reply to
Lasse Langwadt Christensen

Another mystery is why Skybuck's lamp glowed orange hours earlier. When he sees this thread he'll think Prince made it happen from the other side.

Reply to
Tom Del Rosso

So do you. Use an aluminum hat.

Reply to
John S

No but I make them for those like you.

Reply to
M Philbrook

Molten glass has a negative resistance tempco. Hence the original Nernst lamps had series resistors.

NT

Reply to
tabbypurr

Just for interest's sake, how did the electrode-only heating method start up? Heated by some other means?

RL

Reply to
legg

Yes, the glass was permanently molten 24/7 and the factory worked around the clock. IIRC it shut down once a year in the summer for a furnace rebuild. Of course, to restart would require 'conventional' heating.

This bulk electric heating was only used when it was cheaper, so I guess at night.

The final, finely controlled heating stage was as the glass fibre was pulled through overhead finely perforated Platinum plates (called 'bushings' IIRC) which used ohmic heating.

Cheers

--
Syd
Reply to
Syd Rumpo

I'm confused. The bulb filament *must* be broken, else it wouldn't shut do wn. Maybe theres a fracture in the iron filament-support wire. It might d issolve in liquid glass, causing the hot zone to spread. Like putting a 2

5W bulb in series with the 75W filament

Yes, 2012, inspired by my original 2007 video, Melt a Frickn' Beer Bottle

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Here's a version which isn't blocked by youtube as "adults only."

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Reply to
Bill Beaty

Would it liquify?

People have used pieces of white ceramic knives for this. Or, get it from a "knife sharpener" which uses two crossed 1/8" ceramic rods.

Last I was there, Harbor Freight Tool sells both.

Reply to
Bill Beaty

The filaments in fluorescent lamps glow orange when the starter doesn't sta rt up the lamp. Spontaneous orange-glowing edison bulbs are far more weir d.

But mine happened awhile ago ...JUST BEFORE THE CHILEAN EARTHQUAKE, AHA! So Skybuck's probably was a warning for that, not for Prince. We all know that the spirits get confused about things like "past" and "future," and fr equently predict things which have already occurred.

Reply to
Bill Beaty

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