Hello! Today we're going to talk about
the limelight. Some of you may know the phrase "to be in the limelight"
and wondered what exactly does that mean? After all, Rosco does make a lime color
gel but it's not the most flattering of colors. ... so that's the color you're going
for is it ... Bleah. Why would you want to be in that? Well it doesn't refer to the gel. The original effect was actually discovered by a man
with the most British name ever: sir Goldsworth Gurney - it was then turned
into a usable lighting fixture by a Scotsman named Thomas Drummond which is
why you sometimes hear them called Drummond lights. The way that a limelight works is you direct an oxy-hydrogen flame on to a piece of quicklime which
then starts to glow. Now you may be wondering why you had to direct the
flame onto a piece of quicklime instead of just using the flame as a light
source. Theaters used gas lights all the time. Well a gaslight uses a hydrocarbon which means that it's got hydrogens and
carbons in it - you mix it with the oxygen in the air and it turns into water and
carbon dioxide and heat. The carbon glows that nice orange color. If you have a
hydrogen oxygen flame it's much hotter but it's almost invisible. For example,
this is the Space Shuttle main engine firing in a test stand - that motor is using
almost a thousand litres of fuel a second and you can still see through the
exhaust plume. Even when all three of them are firing in a shuttle launch you can still see through them. The
bright light and smoke come from the solid rocket boosters which use a
different fuel entirely. When I first came up with the idea of doing this demo
I had one slight problem: it's not exactly easy to get hold of quicklime these days and when you tell people you're looking for quicklime they start to look
at you funny and think that you're trying to dispose of the body and when
you tell them that you're actually trying to recreate an archaic form of
theatrical lighting fixture they don't look at you less funny. Also, it
doesn't work for disposing of bodies it just kind of masks the smell. So then I looked up "how to make
quicklime". I mean, how hard can it be the Romans used to do it and Wikipedia says
you calcinate limestone. Okay So then I looked up calcination and it
turns out you're just heating it up to about eight hundred and thirty degrees
Celsius and since I was gonna heat it up to about two and a half thousand with my
torch anyway I figured I'd just make the quicklime on the way there. So I went to
the hardware store I bought some limestone tile and I bought a mapp gas
torch although it's actually probably propylene because I haven't made mapp gas
in the US since about 2006 or 2008 I can't remember and got this set up. First a quick safety note: theaters are generally paranoid about fire because we used to
burn down a lot because we used to light our theaters with things like lime
lights and open gas jets and candles. Just not a good scene and even though we
haven't really used any of those open flame fixtures for 100 years or so
we're still paranoid. So in preparation for this demonstration I have taken the
liberty of clearing every flammable thing within about three meters in every
direction. I also have my squeezy bottle full of water. There are one, two, three,
four, five, six, seven fire extinguishers that I can see from where I'm standing
as well as four fire hoses. One there, one down the hallway and two behind me on
stage. I've also got safety glasses and health insurance. So this is what an old
gas light would have looked like, bright flame but very very sooty and
flickery. This is closer to what you would have
gotten with an oxy-hydrogen flame. If you've done oxy acetylene welding this
should look pretty familiar. All right let's try and heat this up nice and
evenly. There, that's what we're looking for. Here is my piece of limestone after
calcination. You can see the top is much different than the bottom half of it.
Calcination is simply driving off the carbon turning it from calcium carbonate
to calcium oxide. (torch hissing noises) Alright, now I'm going to light myself
using only the limelight. There we go! Not green. Actually not a
bad light and also since it was one of the first point sources of light before
we got to electricity this is what would be in a spotlight. Thus if you were in the
limelight you were one of the main characters. Spear carrier #3 could
be off in the gas lights but if you were in the limelight you were an
important person. And now: A lime limelight. ...and now, lighting a lime with a lime lime
light. That was a terrible joke and I should be ashamed of myself. (hissing noises finally stop) Well, I hope you enjoyed this
demonstration. I've got a couple of others that I'm planning on doing. None
of them are particularly as exciting as this one except for maybe the arc light
but hopefully you'll find them interesting and thank you for watching It's fake. (foam bouncy noises) Welcome to theater.
