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hi everyone in this video I'll be
showing you how I recreated a carbon
filament light bulb the first type of
electric lighting that actually made it
out of the lab and into people's homes
there are two people that typically get
credit for this invention depending on
what part of the world you're in the
American inventor Thomas Edison or the
English inventor Joseph Swan both of
these people announced their invention
of the electric light bulb within months
of each other
Joseph Swan being the first however even
though Swan made his announcement first
I believe Edison light bulbs were a more
complete and viable invention for
reasons that I'll dig into as we
actually make one I have to make a quick
note about Thomas Edison before we get
deeper into this video it's very popular
right now to claim that Edison was a
fraud and a thief of other people's
ideas this video is not meant to address
that issue but I will say that having
now spent more than a year researching
him and the people that worked for him
the truth is not that simple Edison was
a very intelligent person especially in
the field of manufacturing one reason
many people now discredit him is because
they don't like that he hired other
brilliant people to work for him and so
why should a dicin get credit for their
work you can look at it that way but
also consider that without Edison this
team of people would not have come
together and worked with their combined
skills on the inventions Edison believed
to be possible it's complicated as are
all the other rumours and bits of
propaganda surrounding him so let's try
to stay humble in our opinions ok that's
enough of that so let's look at one type
of electric lighting that
before Edison before Swan and before
everyone else that experimented with
filament based lightbulbs
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I have in front of me two carbon rods
used as the material of choice because
carbon has the highest temperature
resistance of any conductive material
known in the 1800's attached to these
rods by copper wires is a powerful
source of electricity in my case an
electric arc welder before Edison one
method of electrical illumination worked
like this whew as you can imagine there
are some downsides to using this as a
light source in your home this consumes
tremendous amounts of electricity and
the carbon rods are constantly being
eroded away as the spark jumps across
them there's a danger of electrocution
and to top it off it emits ultraviolet
light which will make you go blind but
it certainly is bright there were
predecessors to both Edison and Swan
that had realized the potential of light
generation by means of incandescence
rather than an electric arc Edison
purchased a patent from a pair of
Canadian inventors who are experimenting
with taking a carbon rod like this one
and shaving it to be thin in the middle
so that when electricity was passed
through the rod the thin portion glowed
the main break through from this patent
was that the emission of light was
improved when the carbon rod was made
narrower and longer to increase its
electrical resistance still they were a
long way off from a mass-producible
design in the attempts to increase the
electrical resistance of these carbon
rods were not good enough
Carbon is very fragile and narrowing the
rods further caused them to break the
design as it was required way too much
power for too little light
in my case I'm still powering this with
my arc welder using much more power than
would have been practical to deliver to
a home in the 1800s in order to make a
carbon wire narrow enough to offer
adequate electrical resistance it became
apparent that it would need to start
that way rather than being whittled down
from a larger carbon rod forming a
narrow piece of carbon which is now
referred to as a filament is relatively
easy if you start with natural fibres
from plants when plant material is
heated to the point of combustion in a
closed container where no oxygen can
reach it everything except the carbon
turns into a gas leaving a blackened
skeleton of pure carbon behind the
carbon resembles the shape of whatever
plant material it came from meaning if
you start with narrow pieces of plant
material you'll end up with narrow
pieces of carbon edison and swan began
experimenting with this concept to
create their carbon filaments at
approximately the same time one
difficulty with this process is that
these filaments are extremely fragile
and it's not easy to connect them to a
piece of wire to supply electricity the
carbon is too fragile to hold in a clamp
and the usual methods of joining metals
together don't work with carbon to make
a secure electrical connection it was
found that the plant fibers that would
form the filaments needed to be joined
to the supporting wires that hold them
in the centre of the light bulb before
they were put into the furnace and
carbonized a putty made of tar and
carbon soot is used as a glue to hold
the filaments to the wires and since
this putty is itself an organic material
it also solidifies into pure carbon this
lump of carbon at either end of the
filament bridges the gap and makes a
solid physical and electrical connection
between the metal wires and the fragile
carbon conductor before we go any
further in this video I want to take
just a minute to talk about this video
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in the workshop good timing Moe's in my
own attempts to test many different
kinds of filaments I found it necessary
to make a stand with a removable glass
dome since the process of blowing a new
glass bulb for every test seemed rather
daunting I use two copper nails pressed
into an insulating piece of ceramic to
hold the organic filaments in place for
carbonization and carbon putty to glue
the filaments to the nails these pieces
of ceramic tile give the filaments a
rigid support structure so I have
something solid to grab onto as they're
moved in and out of the carbonization
chamber for this test I'll be using
twisted pieces of paper towel as my
filament one thing that Edison
discovered rather quickly is that the
conductivity of a filament made from
pure natural fibres was very low so it
had to be helped along by smearing the
material before carbonization with some
of the same carbon soot and tar putty
that's what I've done to this paper
towel I've made my carbonizing chamber
in such a way that I can produce about
half a dozen test filaments at a time
they're placed upside down on a
supporting wire and then some
sacrificial pieces of paper are placed
in the chamber with them so if any
oxygen gets in der
heating hopefully this paper will react
with it before it has a chance to damage
the filaments I use a large soup can as
the actual carbonizing chamber and I
found that spraying the inside of this
can with rubbing alcohol also helped to
improve the quality of the filaments by
reacting with the oxygen that would
otherwise damage them the heating
process takes about 10 or 15 minutes and
then just as long to cool down before I
can safely open the chamber and inspect
the result
you can see how fragile these filaments
are which is why the ceramic base was
necessary to move them around for my
testing each filament is carefully taken
out of the carbonizing chamber and moved
over to my test stand where it sits on
two exposed pieces of copper which makes
contact with the nails that are glued
with carbon putty into the ceramic
support and to the now carbonized
filament there's one last thing to do
before connecting the power the filament
needs to be protected from oxygen so
that it doesn't catch fire and burn away
the instant it's turned on there are a
few ways to do this Edison and Swann's
predecessors most often chose to fill
the glass bulb with an inert gas like
nitrogen but Edison found this wasn't
ideal for the longevity of the filament
in his eventual patent of a successful
light bulb he wrote this the use of a
gas in the receiver speaking of the
light bulb at atmospheric pressure
although not attacking the carbon serves
to destroy it in time by air washing or
the attrition produced by the rapid
passage of the air over the slightly
coherent highly heated surface of the
carbon to put this in simpler terms
Edison believed that the convection
inside the bulb caused by the hot
filament made even inert gases slowly
strip away the carbon by smashing into
it so Edison opted to remove the oxygen
from his bulbs with a vacuum pump and to
do this effectively he had to build a
very good one now I tried using vacuum
to protect my filaments but my vacuum
pumps are not capable of the ultra low
pressures achieved by Edison in fact
that was one of his biggest
contributions to science at the time my
filaments quickly burned up in tests
with vacuum since I don't need my bulbs
to last for hundreds of hours for the
purpose of this video I chose a simpler
method which is to fill my bulbs with a
gas that would react with oxygen even
more easily than my carbon filament
propane if I inject propane into my bald
when the filament heats up any oxygen
left inside should prefer to burn with
the propane leaving the carbon untouched
my bulbs won't last as long as Edison's
due to the air washing effect he
mentions but otherwise they should work
for long enough to demonstrate a
successful result with that let's turn
the power on
this light bulb might not look like much
when it's surrounded by all my video
lights but in the dark it's bright
enough to read by which is not that far
behind the first generation of electric
lighting
one of the key goals for a successful
light bulb was to have a high enough
electrical resistance that it uses only
a small amount of power in return for a
lot of light in this respect my bulb is
still a failure the light is quite dim
paling in comparison to this modern
light bulb which is not just here so I
could show the contrast I'm using this
light bulb wired in series with my test
platform so that it acts like a resistor
to limit the flow of electricity if I
did not have this modern light bulb
limiting the flow of electricity the
carbon filament would draw enough power
to blow every fuse in my workshop let's
try it I'll disconnect the power and
remove the light bulb from my test
platform to reconnect the circuit I'll
instead put a 15 amp fuse in the socket
which will hopefully blow before my main
workshop fuses but until then it should
allow my test bulb to draw as much power
as it wants so let's see what happens
we were able to get a lot of light out
of the bulb for just a moment but at a
cost of way too much power and way too
much heat for the filament to handle so
the ball burnt out and here we have
reached the main difference between the
light bulbs made by Edison and those
made by Joseph Swan this light bulb that
I have created is much like a swan light
bulb in functionality it requires
multiple bulbs to be wired in series so
that each one does not draw too much
power this is what swans light bulbs
also required it's a much bigger
challenge to create a filament that has
enough electrical resistance that it can
stand alone on a circuit being plugged
directly into a power grid Edison's
company was not only inventing a light
bulb at this same time they were also
working on designing the electrical grid
that could power them swans first
patented light bulbs did not take this
into account and for this reason we're
just not practical on a large scale
plugging one in in the wrong
configuration could cause a blackout or
burn down your house as it draws too
much power for the wiring there are
solutions around these problems but the
best one is to just make a better light
bulb in the second paragraph of Edison's
patent we can see that the intention was
not just to invent another electric
light which could work in the lab or on
a small scale in which Swan and others
had already accomplished but to invent a
light that could function in a
real-world application of a power grid
and this is where it gets very
complicated to make a filament that has
greater electrical resistance there are
two ways to go about it you can make the
filament longer or you can make it
narrower in both cases they become much
more fragile and more difficult to work
with I experimented with dozens maybe
more than a hundred different types of
filaments and methods to make them
including making spiral filaments which
come with a whole host of new challenges
with preventing the distortion of the
coil all this with no great success when
the filaments get much longer than what
I've already demonstrated it takes much
more voltage to overcome there
initial resistance the first time power
passes through them after this first
burnin the resistance greatly drops as I
believe the extreme heat actually
converts the filament into a much more
conductive form of carbon graphite
reaching this point for short filaments
can be done with the 115 volts from my
wall outlet but to go any further and
make light bulbs comparable to Edison's
I think I would need a higher voltage
power supply to provide the initial kick
so this is where I stand on this project
I've had the best success with filaments
made from cotton string paper and paper
towel cotton string and paper are both
mentioned in Edison's first patent the
results though are roughly equivalent to
Joseph Swan style light bulbs Edison's
best results were with bamboo
specifically bamboo that had been aged
10 years or more I've had difficulty
with this because all the samples of
bamboo that I could find were not
flexible enough to form tightly curved
filaments even after I tried steam
bending and a few other bending methods
this has definitely given me a new
respect for the invention of electric
lighting
Edison's patent in particular is densely
packed with an entire series of small
but brilliant discoveries that all come
together in the eventual Assembly of a
completed light bulb whether he was
personally responsible for most of these
discoveries or if they are the result of
those he hired the finished product a
working carbon filament light bulb with
high and consistent electrical
resistance is an impressive
accomplishment hopefully you've gotten a
small taste of that from this video
leave me comments below I'd love to hear
from you thanks for watching I'll see
you next time
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