This video is sponsored by NordVPN. It’s really easy. There is no need for
a lot of effort to pop bubbles just with your fingertips.
But if it's so easy to pop, is bubble wrap really effective
to protect our objects?
Franck: Did you hear? Viviane: No, I didn't hear anything.
Did it pop? Franck: I don't think so… No, it didn't pop.
Viviane: It didn't pop??
When bubble wrap was invented in 1957, it was not to satisfy our
strange urges to pop bubbles (whether real or virtual), as you can imagine.
No, it was originally to make wallpaper. Wallpaper that
would be made out of 2 plastic shower curtains glued together, enclosing bubbles.
It was going to be textured, original, avant-garde. Bad luck, it was mostly ugly. At least…
in any case, it didn't work. The inventors Alfred Fielding and Marc Chavannes were
still convinced of the potential of their invention and found it supposedly 400
other uses (but I couldn't find that list). And among these uses, there is
the one you know, which is protecting items. The use that I am about to make
of it, I don't know if it was on their list. I'm stealing the idea from artist
Bradley Hart, who has made his entire career with bubble wrap. So in honor of
the last episode of this season of “I got lost on the internet (again)” - I'll
talk about that at the end of the video - I too will create a work of art based on
the same principle by injecting paint into bubbles. ...It's going significantly
worse than expected. But to get back to our question, when we use this bubble
wrap for its current use which is protecting objects from impacts, does that
really work given that we can burst it just with your fingertips? I went to see
Franck at the lab where he works to play with bubble wrap and see what
we can find out by running a few simple tests.
Viviane: Prediction: how many kg do you think it'll take to burst a bubble?
Franck: 20 kg? (44 lbs) Viviane: I'll say 12 kg. (26 lbs)
This is a compression machine. In this lab, it is used to run
real mechanical tests and not to satisfy the pressing desires of the spectators ;)
We've put a single bubble inside (those around it are popped) and
we'll compress it with the machine. We're trying to find out at which point of compression
it's going to pop. I'm betting on a force equivalent to 12 kg and Franck is betting
on 20 kg. You can play with us and try to guess at what weight applied
to ONE bubble, it will pop.
Viviane: OK let's go… ... what? Franck: do you think it popped? I haven't
heard a pop. Viviane: It didn't pop? But we're
at 100 kg (200 lbs)? Franck: Even more, we're at 120 kg. (264 lbs)
Viviane: It didn't pop! Franck: I'll put 4000. 400kg (882 lbs), come on.
Viviane: But come on... there is no space. It didn't pop ...
Several hundred kilograms... And we have yet to answer the
question of whether it protects things well. But either way, if you want to, for example,
protect your plates, you can stack a hell of a lot of them before reaching the limit of your
bubble wrap. (Now, we're not talking about the amount of plastic
that's in there, we're putting that aside for this video. But… it matters.) It's still pretty
incredible, this 400 kg number. Especially when I clearly don't have 400 kg in my
fingers. That's for sure. That said, the machine and my fingers aren't the same. If you
put your bubble wrap on a table and you don't press on it with your fingers,
but with as flat a surface as possible and keep it as parallel as possible to the table
without moving it around... you won't be able to burst the bubble.
These hundreds of kg are certainly an impressive force, but that's not what intrigues me
most. Can you seen how much that bubble is squished? Where did the air go?
That is pretty mysterious to me. The air is necessarily stuck between
the two plates. But that implies that... This is the behavior of a gas when
we look at its volume in relation to its pressure. In the case of the bubble, when we compress it
and we reduce its volume, we necessarily increase its pressure. But that volume can
never reach zero. So that means that the bubble has flattened to the extreme.
It probably went from a form like this to a shape like this. And the
remaining height is probably in the ballpark of 10 micrometers (394 µin) if my calculations
are good. 10 µm is about the tenth of the thickness of a hair.
It's very, very thin so that's why it looks like the plates
are stuck together. But that means that the pressure is probably very high
in the bubble. So why doesn't it pop? The plastic of the bubble wrap is very
thin. It seems to me it should have burst a while ago. Neither Franck nor I have the answer
so for the first time in a video, I am making a hypothesis, and I am a
little scared to screw it up. So don't take this for absolute truth, I don't have
a PhD in bubbles. According to one of the first patents of the invention, the thickness of the
plastic is not uniform throughout the bubble: it is thicker at the base
than at the top. It's a little bit as if the bubble looked like this: we have more
matter at the bottom than we do at the top. So this part here (the base) should be more
resistant to bursting than the top of the bubble obviously, since
there is more material. In the patent, it is presented as a characteristic of the invention,
but if you want my opinion, this variation in thickness is above all a "happy
accident”, the logical result of the manufacturing process which we will discuss later.
I'm not sure I will achieve anything... In short, the top is weak, the bottom is strong
if we summarize roughly. Besides, it’s something you can see when
you burst a bubble with your hands, it always bursts where the plastic is
thinnest. So why doesn't it burst in our test? We think it's a matter of
friction. The plastic of the bubble wants to stretch out - because as we
compress it, pressure builds up, it really wants to burst, to stretch
outwards. But there is the machine on top of it. And the machine creates
friction which holds the plastic and prevents it from stretching.
So that would be why the bubble doesn't burst -I reiterate, this is a hypothesis—,
simply because the stretching force of the plastic that would cause it to break
is counterbalanced by a frictional force that would be between the machine and the bubble.
This is our hypothesis but I invite you to share yours in the comments. And if
you have access to a compression machine, do not hesitate to
compress bubbles so do you and tell us how it goes for one bubble.
Nice performance by the little bubble. But it is quite paradoxical how it can
be both resistant to pure compression when distributed over its entire surface, but
a little pressure from our little fingers makes it pop. A bubble both fragile and tough,
{lyrics to a famous French song...} Are you starting to guess
what I am drawing? So, my hypothesis... yet another
hypothesis, let's put the special display back on. So my hypothesis as to why it pops
so easily when we use our fingers is that we concentrate the air in a very small
corner of the bubble. Of course, the plastic stretches (should have put it in red,
excuse me) under the effect of air compression, but since it is very thin,
there isn't much to stretch. And what's more, the point where we would have extra plastic,
where we could try to stretch the plastic, that's stuck under our finger.
So inevitably, the bursting of the bubble is the only alternative. End of hypothesis.
I don't know if we really solved the mystery of the incredible resistance of
the bubble at this slow pressure from the machine, but it really tickled mine and Franck's brains
and I hope it tickled yours too. But I would like to circle back to the happy accident
we were talking about earlier. I told you that we would get back to how
bubbles are made, and this is how. To create bubble wrap, you need two
plastic films, one that will go underneath and one that will go on top, that will
pass through a succession of heated rollers to soften them and prepare them for bubble
making. For example, we will have a first layer that goes like this... So we have this
first layer that ends up on that cylinder, which is apparently called
an embossing cylinder. It looks something like that. These rollers have
holes… a kind of female relief. When the film passes over these holes, there is
a mechanism to draw the air inside the hole, and the plastic sticks to and
follows the shape of the cylinder. You might recognize that this technique is called
thermoforming, or in any case it is very similar, which we saw in last month's video.
With that, we have just formed bubbles. This is why just now
I'd said that it made sense to me that the edges of the bubble are thicker at the
base: simply because the manufacturing process ends up quite naturally
with this kind of variation in thickness: it is very stretched at the bottom of the hole, it's not
at all stretched here, and inevitably there is a variation in thickness between the two.
There you have it, a little aside. Anyway, back to our two plastic films.
The second plastic film also passes through some rolls, then over
the top layer. And since both are very hot, at melting temperature, the two
layers merge and the air inside the bubbles is locked up. Basically,
it’s that simple. But we still haven't got the answer to
the original question. Does something which we can burst with our fingers manage
to protect objects in case of a fall? A shock is
not the same as weight that gradually accumulates like when we stacked plates.
Shock is a fast and strong event. So I don't have the equipment to check
the impact resistance capacity of bubble wrap. On the other hand, the operating principle
is known. It’s quite similar to an airbag. (This one was just for fun).
The force of a shock, the one that will be result in an object breaking, is proportional
to mass and speed. Or at least at a speed variation, an acceleration
in any case - the two notions are connected so I'll say speed for now.
Mass, we can do absolutely nothing to change it since the object weighs what it
weighs. On the other hand, speed, we can try to reduce it to a minimum... thanks to
bubbles. In fact, as they can get gradually and slowly deformed, they
accompany and cushion the object that falls, so that if the object ever makes
contact with the ground, once the bubble has been enormously distorted...
Let's say that this is our object. So if it ever comes into contact with the ground, the
role of the bubble wrap is to reduce its speed to its absolute slowest.
The point is to decelerate it as much as possible. This is why a small bubble, even
though it tolerates very high pressure as we saw earlier, it only has
a few millimeters available for compression. It can cushion, but on
a very small distance. While a big bubble probably tolerates a lot
less pressure, but it has a lot more compression distance available. So
take big bubbles for heavy objects that need a lot of cushioning.
Last advantage of bubbles: imagine that the object to be protected is shaped into
a point. If it hits the ground like this without any bubbles, this tiny spot would
take the full force of the shock, and breakage is very likely. When
there are bubbles, not only is speed slowed down, but the bubble conforms to
the shape of the object. So that the force of the shock is distributed over the entire surface...
enough to further reduce the risk of breakage. Now you know everything about the physics of bubbles.
You know what, this bubble wrap topic...
I still have a lot to say about it, that I put aside because I wanted to
focus on the mechanics of the thing, because that's what interests me
most. (That and my silly projects). But there are so many cool things to say
that next week, I will publish another video to answer your questions
on bubble wrap. I already have a lot planned like: what is the air in the
bubble wrap, why are bubbles so wrinkly, why is there bubble wrap
that does not explode, why do we see more and more of the large bubble wrap (this kind
of thing) and less of the small bubble wrap... They are lots of little questions that are
interesting but which have quick answers so that will be in the next video. And
if you watch this video at the moment of its publication, know that I haven't
shot the next one yet. So you can ask your questions in the comments and I will integrate
as many of them as possible in the next video. I'll finish my “painting” now
and I'll show it to you… Ok, it's 1:30am, it took a little longer than
planned but I just finished. I'll let it dry and I hope that tomorrow it won't have
leaked. That was long. That was very, very long.
Otherwise, as I told you in the intro, this was the last episode of season 2 of
"I got lost on the Internet (again)”. A big thank you to the CNC for funding
a large part and to the sponsors for financing the missing part. In the description,
you will find the links to season 1 and season 2. We'll continue to meet here
regardless twice a month, that doesn't change. And I will do my best
to produce a season 3, obviously. That should happen one way or
another because these are topics that come naturally to me. So I'm going to go get
funding (you know how it is, sponsors, CNC, crowdfunding).
And speaking of funding... I think it's time.
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Bye.