okay today I'm going to be teaching you
how to make dark fire so in order to
understand how to make a dark flame
first we have to understand what fire
actually is so fire is what's known as a
partial plasma and what that means is
that most of it is just really hot gas
but a small percentage of it is actually
ionized gas because it's gained so much
energy that it's lost some of its
electrons and the light from fire comes
from when those ions gain their
electrons back they release a photon of
light and so fire in and of itself is a
light source even when you shine a
brighter source of light on it you still
don't get a shadow behind it let me show
you so you can clearly see the shadow of
my hand here
but you can see that the fire doesn't
make a Shadow at all and if you look
really close though you can see slightly
something behind the fire and you can a
little bit tell that the fire is there
but that's just due to the fire heating
up the air around it and it changes how
light passes through the air it bends
the light a little bit basically the
same reason you see a mirage on a hot
day so that's basically what's happening
here so it's not a shadow but it's
changing the refractive index due to
heating up the air and not only does it
not have a shadow but if you put a light
source behind it the light from behind
it can easily pass through it and get to
the camera so you don't see that this is
dimming the light behind it in fact it's
adding light to it and that makes
perfect sense because like I said fire
is a light source and so you see the
light behind it and in addition you see
the fire but it doesn't get dimmer it
doesn't make the light behind it dimmer
but is there a way to make fire dark
meaning is there a way to make it
actually absorb light instead of lit it
off so in order to make dark fire or
fire that absorbs light I need help from
a special kind of lamp and it's called a
low pressure sodium lamp and this lamp
lets off only one specific wavelength of
light so it's a monochromatic light
source as opposed to this white light
that just lets off the full spectrum of
colors okay so this is a low pressure
sodium vapor lamp here so inside here is
a tube and in that tube there's some
Neon gas and you can see every few
inches or so there's some Dots here and
those dots are actually sodium metal and
what happens when you apply a very high
voltage to the ends here the sodium
metal heats up due to the Neon gas
inside heating up and it heats up enough
that it starts to vaporize the sodium
metal then the sodium atoms begin to
ionize and they ionize and recombine
with electrons and in so doing they let
off light but they only lit off light in
one specific wavelength range around 589
nanometers it's actually two very close
spectral lines a 589 and 589.6 but it's
considered a monochromatic light source
because those two wavelengths are so
close together so basically it lets off
light of only one wavelength in a
yellowish orange range the weirdest
effect of a sodium vapor lamp has to be
that it basically turns everything into
a black and white movie so I have here a
tomato and my orange extension cord
watch what happens when I turn on the
sodium vapor light and turn off my
regular light
and everything's black and white
so it's just crazy looking at my own
hands here they basically just look
black and white everything becomes a
total shade of gray and the reason this
happens turning everything black and
white like this is because this is a
monochromatic light source basically the
only thing you can see is either this
yellow light or a lesser shade of it and
so everything in the room is either
reflecting a little bit of this
yellowish light or absorbing in so it
looks a little bit darker so the only
way we're going to get a shadow is if
this fire can actually absorb this
specific wavelength of light
okay let's lie our alcohol on fire
you can see that there's no Shadow to
this flame here light the alcohol and
fire also no Shadow behind it but now
let's see what happens when I stick this
tissue that's soaked in salt water in it
watch this
look at that
you get black fire
so when I stick this in it suddenly you
see a shadow behind the flame and the
flame also turns black
so I can assure you that what you're
seeing now isn't camera trickery or
anything it actually looks like what
you're seeing it actually even looks
cooler in person because it actually
looks like black fire when I stick this
in it so what's happening here is that
this has sodium atoms in it and those
vaporized sodium atoms can now absorb
the wavelength of light coming off the
sodium vapor lamp because it's the same
wavelength the same atoms and so
basically we create a fire that can
absorb light
so cool okay I've discovered something
even cooler than just sticking the
tissue in it if you drop a stream of the
sodium chloride water in it then you get
this black flame coming out of it
so awesome look at that black fire it's
totally black
[Music]
okay so I have to say I've done a lot of
experiments on my channel and out of all
of them this has to be one of my
favorites this is so cool to see in
person it's so cool to see the flame
actually turn black it looks like I'm
watching a movie or something and
there's a special effect happening in
front of me this is so awesome
it's this is not smoke there's no smoke
coming off of it whatsoever but this is
black fire
that is so cool
okay look at this black fire
so it's definitely hot this is not smoke
but it is fire
hey everybody thanks for watching
another episode of the action lab I hope
you enjoyed it if you did hit the
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