Limelight - what does the lime do?

[Nickrz]

From Merriam Webster:

Main Entry: 1 lime·light
Function: noun
Date: 1826

1 a : a stage lighting instrument producing illumination by means of an oxyhydrogen flame directed on a cylinder of lime and usually equipped with a lens to concentrate the light in a beam b : the white light produced by such an instrument c British : SPOTLIGHT

What function does the "cylinder of lime serve"? Does it fluoresce or what? Has anyone ever seen one of these things?

[sly]

From EB online:

Thomas Drummond's light, which consisted of a block of calcium heated to incandescence in jets of burning oxygen and hydrogen, provided a soft, very brilliant light that could be directed and focussed. Its intensity made it useful for spotlighting and for the realistic simulation of effects such as sunlight and moonlight. Limelights placed at the front of the balcony could also be used for general stage illumination, providing a more natural light than footlights. The expression "in the limelight" originally referred to the most desirable acting area on the stage, the front and centre, which was brilliantly illuminated by limelights.

[Nickrz]

Wow, thanks. Dangit, you're gonna get me to subscribe to that EB, ain't you?

[mr john]

You put de lime in de... wha? oh. never mind.

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Signitorily yours, Mr John
" Pardon me while I have a strange interlude."-Marx

[AWB]

(Note: I tried to send this Saturday, but the server was down.)
Nickrz,
James Burke did a "Connections" episode that incorporated the development of limelights.

The lime doesn't fluoresce (which needs electricity), but rather it glows when it gets superheated like a white-hot poker. A parabolic lens/mirror is used to direct the light in a beam.

This was a boon when it was invented (in the early 1800's, IIRC). Now theatres could illuminate the action on stage and diversify when and where they held performances.

They were phased out when electricity provided a safer means of producing a glowing light source. But the basic design of today's spotlights is the same.

Nowadays, "limelight" is more commonly used to mean "in the public's attention" or "popularity".

[Nickrz]

"The basic design of today's spotlights is the same"? I take it you mean "with the exception that the glowing cylinder of lime and flammable gasses have been replaced with electricity and an incandescent filament."

Speaking of which, what are they using for filaments in stage/cinema lighting these days? Don't we have some camerapeople/lighting technicians out there?

[John W. Kennedy]

Actually, serious spotlights still use carbon-arc lamps -- an electric arg between two graphite rods. The color is closer to sunlight than incandescent.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[torq]

I believe that most of the stage lamps I use are tungsten/halogen. We've got a few PAR lamps (which are basically large round automobile headlights), and I'm not entirely sure what those are made of. Fixtures which use lamps that are basically oversized "normal" tungsten filament incandescent bulbs aren't uncommon for "low power" (less than 500 watts or so) applications.

I've heard that at one time in Europe fluorescent lamps were used, but I don't know if that's still true now. The problem with them is that they're a lot more complicated to dim than an incandescent bulb.

[AWB]

Nickrz: "The basic design of today's spotlights is the same"? I take it you mean "with the exception that the glowing cylinder of lime and flammable gasses have been replaced with electricity and an incandescent filament."

Yeah, that's what I meant: the light source is different, but the parabolic mirror with the light at the focal point is the same.

[John W. Kennedy]

Flourescent lights also have spiky spectra that don't mix well with other lights and look queer to the camera.

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John W. Kennedy
"Compact is becoming contract; man only earns and pays."
-- Charles Williams

[torq]

That's true also, though it's a bigger problem for camera work than for stage lighting. Still, you can get unanticipated interactions with certain pigments if the spectrum is spiky enough.