Kind: captions
Language: en
glass is inherently brittle it is the
very symbol we use for fragility but
these days we expect so much from this
material we want it to be perfectly
transparent scratch resistant thin and
even flexible but most of all we want it
not to break so is it possible to make
unbreakable glass well in this video I
will make the case that glass is one of
the most important materials humans have
ever made it is transformed how we live
launched numerous scientific revolutions
and forever altered how we think about
our place in the
universe part of this video was
sponsored by
s in mid2 2006 Steve Jobs had a problem
Apple was working on the first iPhone
set to be released in January 2007 but
jobs wasn't satisfied with the screen
the prototypes he was testing had
plastic screens which scratched easily
so jobs wanted glass
but regular glass wouldn't work it too
would get scratched up and it would also
shatter plus he wanted the phone to be
slick so the glass had to be really thin
so he called up the CEO of Corning
Wendell weeks to ask him to make the
glass for apple and 6 months later it
was on the first iPhone this was Gorilla
Glass gorilla glass has been used in
phones computers and wearable devices
for the last 17 years now it's used on
billions of devices and over the years
it's become a lot more
durable so we sent for tassium producer
Peter to corning's headquarters to see
for ourselves how Gorilla Glass is made
and how it works we'll need a volunteer
yeah yes that's me all right so this is
what we call our key scratch demo in
here we have a polycarbonate which is
basically a plastic and then we have a
griller glass and what you can do is
scratch this side first polycarbonate
see how it goes yep definitely scratches
yep trying to scratch in our logo it's
not quite there you go are we getting
veritasium yes all right so now try the
same thing on the other side so this is
Grill glass yeah definitely definitely
does no
scratch to break glass requires two
things a flaw and stress to introduce
the flaw they sand blasted a spot in the
middle of the glass to roughen up itself
surface and Peter will apply the stress
take that tip and put it inside that
Circle and push down see if you can
brece it
for not too hard right no all right so
next we have strengthened soda lot
strengthened as much as you can for soda
l so all
right harder for sure a little bit next
we have gorill glass I'm kind of
terrified oh map
right I know like we don't actually want
to do this but I want to do this
so are you kidding
me there's two
respon the first response is either this
is a really great demo I completely
understand what you're showing me the
second response is I'm taking this
person need to tr to break this SL okay
uh it is a very good demo I've like
you're really impressed at this point uh
I still want to
break right last
one no like I'm I'm bending the
stylus okay
[Music]
amazing glass has existed in nature for
billions of years it's formed by
meteorite impacts lightning strikes and
volcanic eruptions but when humans came
along they found ways to use glass
obsidian is volcanic glass it forms when
lava cools quickly it's extremely
brittle so when you hit it with another
rock you can chip off sections of it to
make a sharper and Sharper Edge there's
evidence of obsidian being used for
cutting implements Arro heads and tips
of Spears as early as 1.2 million years
ago and it hasn't gone out of fashion
today some surgical scalples have their
tips sharpened to just 3 nanm across and
and the best material for this purpose
is
Obsidian compared to the million plus
years we've been using glass we only
started making it very recently around
5,600 years ago most common glass is
composed mainly of oxygen and silicon
the two most abundant elements in
Earth's crust in nature you find them in
the form of quartz crystallin silicon
dioxide crystallin means that the atoms
are arranged in a regular repeating
structure and quartz is the primary
constituent of sand so if you take some
sand heat it up to about 1700° cus until
it melts and then rapidly cool it it
forms
glass during the rapid cooling process
the atoms don't have enough time to
return to their periodically arranged
crystal structure so instead they are
stuck where they are like a liquid
that's been flash frozen in place that
is why glass is considered an Orphus
solid amorphous just means disorganized
not in any regular Arrangement but
perhaps this is where the misconception
about glass being a liquid comes from it
isn't a liquid at room temperature glass
is solid because the atoms are fixed in
place they can't flow past each other
like in a liquid I even made a video
about this 9 years ago they are
disordered but they are
solid this amorphous structure is also
what makes glass so brittle because
there's no way for the structure to
relieve stress when stress is applied to
the glass A small crack will form at a
flaw on the surface and as the glass
cracks the stress is applied to atoms
with fewer neighbors so the crack grows
bigger which eventually leads to the
glass
fracturing so next we'll move to what we
call slaper Demos what we're using is
sandpaper um this represents like an
asphalt cut surface sure so if you were
to get out of your car and you
accidentally drop on in the park M and
what we're using is this fixture it's
bending it so it's pre-stressing it we
have our rough surface to introduce fla
and I'm Ge we Al glass is similar to
some thetive stuff different things onm
and when you're ready you can dve on
three two
one some
sounds okay all right so broke not what
you want to see when you pick up your
phone off the park no heart break and
then we have a gorilla glass and what we
call the mega slap right very exciting
name right now you can see me
dramatically increase the height and I
do it from J no from very top from the
very top okay so we're not just
increasing the height we're also
starting from way up here right all
right 3 2
1 no we're good that's pretty cool
while the basic recipe for glass
involves silicon dioxide glass makers
have been adding other ingredients to
change its properties for thousands of
years adding sodium carbonate also known
as soda and calcium oxide also known as
lime lowers the temperature at which it
becomes liquid from 1700° C to around
1,000° C and that's why sodal lime glass
accounts for around 90% of all glass
manufactured today another recipe
includes adding Boron trioxide to the
mixture
forming a boros silicate glass glass is
usually quite sensitive to changes in
temperature if you throw boiling water
on your car's windshield it'll likely
shatter due to the glass rapidly
expanding but boros silicate glass has a
really low coefficient of thermal
expansion it doesn't grow or Shrink very
much even with drastic temperature
changes so it's often used for
laboratory glass like
beakers let's
go you want to grab a pair of these
green glasses too yeah heavy oh yeah I
can't see
any and while this specific recipe for
Gorilla Glass is secret it is based on a
combination of silicon aluminum
magnesium and
[Music]
sodium and the recipe keeps changing the
scientists are constantly trying
different formulations to find more
durable and scratch resistant glasses
here this is so cool do you ever feel
like a pizza chef
right
[Music]
good this facility is actually where
that experimentation takes
[Music]
place the earliest human-made glass was
likely an accident people had been
working metal for thousands of years
before they made glass so it's thought
that some sand made its way into
metalworking furnaces forming small
glass beads but soon glass making became
its own art form to make decorations
ornaments statues table wear and
containers unlike clay glass is
impermeable to water making it an ideal
material for bowls and Bottles but then
glass makers noticed that by adding
other elements into the mix they could
change the color of the glass by adding
Cobalt oxide you would get a vivid blue
adding cerite makes red
but all of the historical glasses we've
been talking about have been opaque
which is not really what we think of as
glass today after glass making was
invented thousands of years passed
before we invented transparent glass
that's because making it is actually
pretty
difficult the first step came around 100
AD when glass makers in Alexandria added
manganese dioxide into the mixture which
led to a semi-opaque glass it definitely
wasn't transparent but it did let
sunlight
through this is when glass began being
used for Windows and glass windows were
a huge deal I mean they provide a
physical barrier that keeps the warm air
in and the wind and critters out while
still allowing light to shine into your
home but the first truly transparent
glass was made many centuries later
around the Italian city of Venice the
art of glass making was thriving and
bringing a lot of money into the city
there was just one problem to make and
manipulate glass you need very hot
furnaces and at the time Venice was a
City built almost entirely out of wood
so yeah glass makers were bringing a lot
of money into the city but they also
kept accidentally burning it down so in
1291 the government of Venice had had
enough so they moved all the glass
makers to the island of
Morano the island became known as the of
glass celebrated for making the most
beautiful and intricate glasswar
anywhere on Earth this is also where the
glass maker Angelo barovier invented
clear glass he took some seaweed rich in
potassium oxide and manganese and burned
it to create Ash then he added this ash
into his glass and when it cooled he
found that the glass was
[Music]
transparent most materials are opaque
because when photons hit them the
photons are absorbed the photon excites
an electron pushing it up to a higher
energy level but this only happens when
the photons energy matches the energy of
an allowed electron transition and
different materials have different
energy
levels in transparent glass the energy
required to move an electron from a
lower state to a higher state is higher
than the amount of energy that a photon
a visible light has so the photon just
passes right through now while glass is
transparent to visible light it does
interact with other parts of the
electromagnetic spectrum it absorbs much
of the ultraviolet spectrum because UV
photons have more energy hence they can
push the electron to the higher energy
level and be absorbed that makes it
opaque to
UV this is also how colored glass is
made you add impurities into the glass
which affects the electron energy levels
which then changes the color of the
glass if you look at a pane of glass
side on you might notice that it looks
slightly green which is because the most
common glass used for Windows soda lime
has impurities of iron oxides which give
the glass A green tinge the glass
absorbs more of the other colors than it
does green so that's why we see
it I think the only way we truly
appreciate how important transparent
glasses would be if all of a sudden it
disappeared so your windows glasses
screens all gone but there is another
element in our daily lives that we take
for granted which is connectivity I mean
we are always connected to the internet
and losing that connection even for a
few minutes can be pretty uncomfortable
especially when you're traveling staying
connected abroad requires either paying
exorbitant roaming fees or a continuous
hunt for public Wi-Fi but luckily you
can avoid all of this with today's
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want to thank Sy for sponsoring this
part of the video and now back to
transparent
glass truly transparent glass was a
massive deal for 3 three reasons
sometime in the early 1300s in Northern
Italy this clear glass was ground shaped
and Polished into small discs that were
thicker in the center than at the edges
due to their resemblance to lentil beans
they became known as
lenses glasses to correct farsightedness
didn't seem all that important at the
time because literacy rates were so low
they were almost exclusively used by
monks but after the invention of the
printing press Circa 1440 glasses became
a vital tool the printing press led to a
precipitous drop in the cost of
producing books which led to a rapid
increase in literacy rates now a large
number of people became aware that they
were farsighted thankfully there was a
technology available to solve the
problem 150 years later a father and son
Hans and Zacharias Johnson put two
lenses in line with each other rather
than side by side and this was likely
the world's first microscope it made
objects appear about 20 times their
original size in the 1660s antthony van
leuan hook made significant improvements
on the microscope by grinding the lenses
himself he could magnify things 200
times allowing him to see human
cells a few years later Robert Hook
published micrographia a book full of
beautiful sketches of the microscopic
world and all all of this was possible
because of transparent
glass and in 16008 Hans liers an ey
glass maker applied for a patent for a
spy glass his idea was for it to be used
in Warfare to spy on your enemy on the
battlefield but the next year Galileo
galile heard about his idea and realized
that he could point this device toward
the sky to study the stars and
planets Galileo's telescope magnified
objects in the night sky by about 30
times in 1610 he was able to see the
craters of the Moon in detail the phases
of Venus and four of Jupiter's largest
moons these observations were the final
nail in the coffin for the geocentric
model of the universe he saw moons that
were clearly revolving around Jupiter
and not the Earth and how else could you
explain the phases of Venus rather than
to say that the planet must go around
the
Sun none of this would have been
discovered without the invention of
transparent
glass four centuries later we can now
make glass that is orders of magnitude
more transparent than water glass that
is so transparent that if you were able
to make a column as deep as the Mariana
Trench you'll be able to see all the way
to the
bottom this is the glass inside Optical
[Music]
fibers oh this is do real I'm
soap but the main thing we all need is
durable glass so how do you take a
substance that is typically delicate and
brittle and improve its scratch
resistance and drop
resistance first you start with an
aluminum silicate base and then after
the glass is made you submerge it in a
potassium salt solution at 420° C yeah
it really does look like water doesn't
it yeah and don't know if I want to
drink it potassium and sodium are
chemically very similar I mean they both
have one electron in their outer shell
so during this process some of the
sodium atoms are replaced by potassium
atoms in the glass now potassium atoms
are physically larger than sodium atoms
but the glass is already set it's rigid
so it doesn't increase in size so now
there's the larger potassium atoms all
squeeze together taking up the same
amount of space as before this increas
es the compressive strength in the
surface of the glass which makes it more
durable can you see any visual
difference sides between me
home honestly no I have two pieces of
glass one of them has gone through the
iron exchange process the other one
hasn't I don't know which one is L and
uh we're going to figure that out really
soon every
ready 3 2 1
[Music]
okay that's really
cool can I you get it harder
yeah that was a thunk my mind is
genuinely blow that's really cool that's
all just like I exchange right that's
all
just there's no other difference right
you just put it in a bunch of salt yep
for a few hours fall off yep I'm trying
to think of a good analogy for this you
know I can imagine if there were just a
whole bunch of people sort of standing
around casually and you try to run
through them you'd probably be able to
bounce through a few of them break
through the crowd but what if instead
all of those people were squeezed
together shoulder-to-shoulder you know
like people trying to get into a Subway
or something if you try to run through
them all of those forces are just going
to add up and prevent you from getting
in or for making a dent making a crack
anything like
that but the scientist Corning are
constantly trying to refine the process
to make the glass even more durable
there is a whole team at the facility
that is dedicated to testing and
measuring different glass prototypes all
right we're displacing it by 1 and 1/2
mm yep 2
mm who and they really put the glass
through its Paces conducting bending
tests scratching tests and dropping
heavy steel balls onto the Glass 3 2
1 they also have replica phones with
different glasses for the screen and
they drop them from ever increasing
Heights but we can go up a little bit
and maybe right maybe we can imagine
that I'm taking a selfie all of this is
to make the next version of Gorilla
Glass even more durable than it already
is like are we doing this if you want to
oh yeah 1.7 m that's roughly selfie
height 3 2
1 amazing go down and pick that up Still
Still survived D that's pretty wild you
know I think it's rather ironic that we
are making this video right now while my
phone uh looks like this I don't know
can you see those yeah uh so it's still
glass it still cracks it is not perfect
yet but it is constantly improving
because scientists are working on ways
to make this material more and more
durable and we have come such a long way
I am just appreciative that I can have
this material and and it is amazing even
if it does still crack
sometimes with people who just refuse to
get a case for their phone