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How Aerosol Cans Work · Stuff You Should Know

• 0:01
  Speaker 1: Welcome to Stuff you Should Know from House Stuff Works
• 0:04
  Speaker 1: dot com. Hey, and welcome to the podcast. I'm Josh Clark.
• 0:13
  Speaker 1: There's Charles W Chuck Bryant, and this is Stuff you
• 0:17
  Speaker 1: Should Know podcast. Yeah, what are you excited about this one?
• 0:23
  Speaker 1: I'm going to try to be excited for everybody enough
• 0:26
  Speaker 1: for everybody, because I imagine, like there's a you know,
• 0:29
  Speaker 1: there's a lot of people out there who don't listen
• 0:31
  Speaker 1: to every single episode. I just I find it biting
• 0:34
  Speaker 1: in weird because I do that with my podcast. So
• 0:37
  Speaker 1: if I'm like, if I'm listening to like if I
• 0:40
  Speaker 1: look at Mark Marrin', so I listen to that one.
• 0:42
  Speaker 1: If it's a guest that I'm not super into, I
• 0:44
  Speaker 1: want right, that's other podcasts. I'm talking about Stuff you
• 0:47
  Speaker 1: Should Know. Man, you must be confused. Yes, I feel
• 0:50
  Speaker 1: like every single one of them is worth listening to.
• 0:53
  Speaker 1: I agreed. I suspect though, that people are going to
• 0:55
  Speaker 1: skip over this one. Well, I am going to take
• 0:58
  Speaker 1: the rap because I picked this out. I like it,
• 1:01
  Speaker 1: but as I looked into it, I was like, you
• 1:02
  Speaker 1: know what, I don't know how an aerosol can work,
• 1:05
  Speaker 1: and I would like to and it's not super complicated.
• 1:09
  Speaker 1: It's not. In a matter of fact, now that you
• 1:12
  Speaker 1: read this and researched it, you understand how an aerosol
• 1:14
  Speaker 1: can works. You can go to the hardware store on
• 1:17
  Speaker 1: a Saturday when your board is just stand around and
• 1:19
  Speaker 1: explain it to people and get like applause. I could
• 1:21
  Speaker 1: do that. Every anyone who listens to this episode will
• 1:25
  Speaker 1: be able to do the same thing. That would be
• 1:26
  Speaker 1: like ACE Hardware, and there'll be some seventy five year
• 1:29
  Speaker 1: old guy with the red vest next to me. Like
• 1:31
  Speaker 1: all piste off, they always have old timer's working there. Well.
• 1:34
  Speaker 1: They are big on keeping the economy going on the
• 1:39
  Speaker 1: backs of aged baby boomers and that there's a slogan, Yeah,
• 1:44
  Speaker 1: I think it's ACE is the place. Well, you have
• 1:47
  Speaker 1: to read between the line, Um, chuck. Have you ever
• 1:50
  Speaker 1: seen a movie called Style Wars. It's a documentary from
• 1:56
  Speaker 1: Uh no, I haven't. It's pretty cool man. It's it
• 1:59
  Speaker 1: basically arnicles the the rise of graffiti, hip hop, clothing
• 2:06
  Speaker 1: and stuff, and break dancing, just that whole culture. And
• 2:09
  Speaker 1: it's amazing the stuff that people were doing, like even
• 2:12
  Speaker 1: back then as far as graffiti goes, and breakdancing and
• 2:15
  Speaker 1: hip hop and all that, sure, but it's just like
• 2:17
  Speaker 1: the seminal documentary that you just kind of have to see.
• 2:19
  Speaker 1: It's just so cool. It's like it kind of makes
• 2:22
  Speaker 1: you feel cool watching it, you know what I mean? Well,
• 2:25
  Speaker 1: I need that in my life. But the what the
• 2:27
  Speaker 1: reason I raised style Wars is because the graffiti that
• 2:32
  Speaker 1: was being carried out would not have ever been able
• 2:34
  Speaker 1: to be done had it not been for a Norwegian
• 2:38
  Speaker 1: engineer named Eric Rothheim who in put in the first
• 2:43
  Speaker 1: patent for an aerosol can in Norway and then five
• 2:47
  Speaker 1: years later the first one in the US. Yeah, and
• 2:50
  Speaker 1: they had the little photo of some of his initial drawings,
• 2:52
  Speaker 1: and the author of this article points out that although
• 2:56
  Speaker 1: it has evolved somewhat, it's he's He was pretty right
• 2:58
  Speaker 1: on with that first, is right, you know, almost out
• 3:01
  Speaker 1: of the gate, because as we said, it's kind of simple.
• 3:05
  Speaker 1: The Yeah, one of them was simple to me. One
• 3:07
  Speaker 1: of them I didn't quite understand. Well, okay, so um
• 3:11
  Speaker 1: so Rothheim he comes up with this, this patent files,
• 3:13
  Speaker 1: it kicks back and waits for the money to come
• 3:16
  Speaker 1: rolling in, but it doesn't. It took many many years
• 3:21
  Speaker 1: or so maybe a little less before anyone fully understood
• 3:25
  Speaker 1: the value of an aerosol can, and it was um insecticides,
• 3:29
  Speaker 1: bug bombs, cans of um insects spray that was being
• 3:34
  Speaker 1: used by soldiers in the Pacific and World War Two.
• 3:37
  Speaker 1: When people finally said, oh, that is a good idea. Yeah,
• 3:42
  Speaker 1: I wonder if I mean they had atomizers and things
• 3:44
  Speaker 1: at the time. I wonder if that was his initial
• 3:46
  Speaker 1: inspiration was to take that concept and jam it into
• 3:51
  Speaker 1: a can basically, because that's what's going on. Yeah, you're
• 3:56
  Speaker 1: atomizing product. Yeah, and there's a lot of um advantages
• 4:01
  Speaker 1: to atomizing. Number one, if you spray something in a
• 4:03
  Speaker 1: fine mist, it doesn't hit the ground. Is a bunch
• 4:06
  Speaker 1: of liquid that seeks into the groundwater usually sticks to
• 4:09
  Speaker 1: whatever you're spraying it to. Sure, and it's delightful if
• 4:13
  Speaker 1: you wear perfume or have you ever like had the
• 4:16
  Speaker 1: rose water sprayed on your face, like the face sprays. Oh,
• 4:18
  Speaker 1: I thought you meant like an aerosol can of perfect
• 4:20
  Speaker 1: no atomizing in general? Yeah, sure, sure, I'm fresh. I've
• 4:25
  Speaker 1: I've had an avian sprits sprayed on my face. You
• 4:29
  Speaker 1: mean I have before? It's very nice. Yeah, I've had
• 4:30
  Speaker 1: like the rosewater. Emily will spraying me occasionally. It's very nice.
• 4:34
  Speaker 1: It just feels good. Does she like hide behind around
• 4:36
  Speaker 1: a corner and yeah, no, that's the mace. Oh she
• 4:40
  Speaker 1: mazes me occasionally for kicks. Um. So yeah, there's advantages
• 4:46
  Speaker 1: to atomizing things. There's reasons. It's at the very least
• 4:49
  Speaker 1: it's lovely. It is um and the whole premise behind
• 4:54
  Speaker 1: this though, the delivery method of an aerosol can Like
• 4:58
  Speaker 1: we said, it's very basic, it's very old, and all
• 5:01
  Speaker 1: you have to do is understand a little bit about
• 5:03
  Speaker 1: fluid dynamics to to get what's going on. So let's
• 5:08
  Speaker 1: let's do let's give a brief prime around fluid dynamic
• 5:11
  Speaker 1: shall yeah, and fluid period Like you know, fluid isn't
• 5:14
  Speaker 1: necessarily liquid like you might think it's an actual thing.
• 5:18
  Speaker 1: Fluid is any kind of substance that has free flowing
• 5:22
  Speaker 1: particles that it's made up of that and it could
• 5:24
  Speaker 1: be something liquid, could be something gas that those are
• 5:27
  Speaker 1: both fluids. It just can't be a solid basically pretty much. Yeah, yeah,
• 5:32
  Speaker 1: as long as you got those free flowing particles. Um,
• 5:35
  Speaker 1: these particles, uh, if it's a liquid, they're loosely bound,
• 5:38
  Speaker 1: but they're still bound. So it means it's gonna have
• 5:40
  Speaker 1: a fixed volume if it's a liquid. Yeah, which is why,
• 5:42
  Speaker 1: like when you put water into a glass, it doesn't
• 5:46
  Speaker 1: just keep going and going and going. That'd be terrifying. No,
• 5:49
  Speaker 1: it would make it. It would have a gaseous um characteristic.
• 5:53
  Speaker 1: Then that's right, because gas does expand to fill the
• 5:56
  Speaker 1: volume that you put it in. That's right, and well,
• 5:59
  Speaker 1: spoiler or that's what happens with gas. It expands. Uh,
• 6:03
  Speaker 1: if you heat liquid um applying energy to it, basically
• 6:07
  Speaker 1: it's gonna vibrate and it's gonna break those forces and
• 6:11
  Speaker 1: they're not gonna be bound together anymore. Then you're gonna
• 6:13
  Speaker 1: have a gas. And that's called boiling. Yeah. And I
• 6:16
  Speaker 1: mean we think of boiling is like applying enough heat
• 6:19
  Speaker 1: that you will burn your skin. But boiling points vary
• 6:23
  Speaker 1: for different types of fluids. Um. So any volatile fluid
• 6:27
  Speaker 1: is a fluid that um boils or turns from a
• 6:30
  Speaker 1: liquid state to a gasy state. That's boiling um at
• 6:33
  Speaker 1: room temperature, right, Yeah, Which that that's the part I
• 6:36
  Speaker 1: had a hard time getting my head around because I
• 6:39
  Speaker 1: associate boiling with like heat and hot. Yeah. Because you
• 6:42
  Speaker 1: think of boiling, you think of water, Yeah, exactly. And
• 6:44
  Speaker 1: it takes a certain amount of temperature, of heat of
• 6:48
  Speaker 1: heat energy to break those intermolecular bonds to turn water
• 6:52
  Speaker 1: from a liquid into a gas, that's right. But it
• 6:55
  Speaker 1: takes less for alcohol or for propane or whatever you
• 6:58
  Speaker 1: want to use. Right. And so lastly there's another fluid
• 7:02
  Speaker 1: dynamic trait that we have to have down and then
• 7:04
  Speaker 1: we'll have all of the stuff in place to understand
• 7:08
  Speaker 1: an aerosol can expansion of gas. Yeah, So so we
• 7:12
  Speaker 1: said that when you put gas into something and expands
• 7:14
  Speaker 1: to fill the volume, Yeah, and gas will decrease in
• 7:18
  Speaker 1: pressure as it expands, which is why like a tiny
• 7:22
  Speaker 1: little CEO two cartridge, it's like got tons of pressure
• 7:25
  Speaker 1: in there, and that's why it can shoot your awesome
• 7:28
  Speaker 1: industrial arts model car down the track. Because did you
• 7:32
  Speaker 1: ever do that? Really? I had a Pinewood Derby racer once.
• 7:37
  Speaker 1: What's that like the car you sit in? No, that's
• 7:40
  Speaker 1: the cub scout car. Okay, it didn't have any CEO
• 7:43
  Speaker 1: two though you'd be immediately disqualified. Yeah. In high school,
• 7:46
  Speaker 1: we we made the little cars that have the CEO
• 7:48
  Speaker 1: two cartridge in the battle. I know what you're talking about.
• 7:50
  Speaker 1: And we raced each other and my brother one county
• 7:53
  Speaker 1: of course, and then and then flashed this winning smile,
• 7:56
  Speaker 1: and three years later, it's so funny. I forgot all
• 7:58
  Speaker 1: about this. I tried to be his car design when
• 8:01
  Speaker 1: I took the class, and mine was not nearly as like,
• 8:06
  Speaker 1: it just wasn't quite right, and I didn't win county.
• 8:09
  Speaker 1: I didn't even win my classroom. Somehow, the the compressed
• 8:14
  Speaker 1: air decompressing into the atmosphere made like a sad trombo
• 8:17
  Speaker 1: and sad is it so cool? And that really kind
• 8:20
  Speaker 1: of just sums it all up with my brother and I.
• 8:22
  Speaker 1: He was always really great at stuff, and I always
• 8:24
  Speaker 1: tried to do that and was not nearly as good
• 8:27
  Speaker 1: at it. You're good at other things. Well, I'm yeah,
• 8:30
  Speaker 1: I can run my mouth, if that's how you want
• 8:33
  Speaker 1: to put it. Anyway, So that's compressed gas. And when
• 8:37
  Speaker 1: gas is compressed, it can you know, do some great
• 8:39
  Speaker 1: things like shoot the car or in this case, spray
• 8:42
  Speaker 1: paint or something. Right, right, exactly, Okay, So you have
• 8:47
  Speaker 1: compressed gas, you have all these fluid dynamics, and you've
• 8:49
  Speaker 1: had everyone now right, Okay, So all an aerosol can
• 8:53
  Speaker 1: is is all of these principles kind of put into
• 8:56
  Speaker 1: a very simply mechanically functioning state. Right. Yeah. So you
• 9:02
  Speaker 1: have a can and you have to to things in there.
• 9:07
  Speaker 1: You have the propellant, which is the stuff you use
• 9:10
  Speaker 1: to force the other thing, the product out. Yeah. And
• 9:14
  Speaker 1: it could be hair spray, bug spray, could be painting oil,
• 9:19
  Speaker 1: could be that foamy stuff you ever use that, the
• 9:23
  Speaker 1: stuff to like seal like insulation or sure or like
• 9:26
  Speaker 1: fix the flat. All that, all that has myriad myriad uses. Okay, right, So, um,
• 9:33
  Speaker 1: you've got the product in liquid state. Yes, uh say,
• 9:36
  Speaker 1: it's just kind of floating in the bottom of the can.
• 9:39
  Speaker 1: You put it in the can, seal it so it's
• 9:43
  Speaker 1: there's there's no air going it's air tight. Yeah, this
• 9:45
  Speaker 1: is part one. There's two two ways to do this.
• 9:47
  Speaker 1: This is the first, right, This is the simple way.
• 9:49
  Speaker 1: And then you add some sort of compressed air to it,
• 9:53
  Speaker 1: call it air compressed air. Okay, okay. So you have
• 9:58
  Speaker 1: this um the propellant in there, and it's it's basically
• 10:02
  Speaker 1: filling up as much of it as it can until
• 10:04
  Speaker 1: it's reaching the top of the can, the side of
• 10:06
  Speaker 1: the can, in the top of the water, and it
• 10:08
  Speaker 1: pushes all that product down to the bottom, which is
• 10:10
  Speaker 1: one reason you gotta shake it chack it up exactly.
• 10:13
  Speaker 1: So you have a tube going down from the nozzle
• 10:16
  Speaker 1: at the top of the can valve system all the
• 10:19
  Speaker 1: way down to the bottom of the can where the
• 10:22
  Speaker 1: liquid is right and that look, that valve has a
• 10:25
  Speaker 1: seal that's being pushed up by a spring. So the
• 10:29
  Speaker 1: head the nozzle when it's when it's not being pushed,
• 10:32
  Speaker 1: it's stealed tight. But when you push it down a
• 10:35
  Speaker 1: channel opens. It goes below the seal and you now
• 10:40
  Speaker 1: have the outside atmosphere, which is at a much lower
• 10:43
  Speaker 1: pressure than inside the can um opened up to the
• 10:47
  Speaker 1: inside of the can at that much higher pressure, and
• 10:50
  Speaker 1: it drives it up the tube out the little tiny,
• 10:53
  Speaker 1: tiny hole which atomizes it. And that's basically the simpler
• 10:58
  Speaker 1: method of the aerosol can. Yeah. The air pushes the
• 11:00
  Speaker 1: liquid down and then up the tube. Yeah, because it's
• 11:02
  Speaker 1: like I want to get out too exactly. It expands. Done.
• 11:07
  Speaker 1: I mean that's pretty easy. Yeah. So the second way
• 11:10
  Speaker 1: that this can happen, and I didn't know this is
• 11:12
  Speaker 1: the more common way, but it is. Uh they use
• 11:14
  Speaker 1: liquified gas, so uh, that is the propellant. You've still
• 11:19
  Speaker 1: got the same product. And the product is is sitting
• 11:23
  Speaker 1: there at room temperature just fine as a liquid. So
• 11:25
  Speaker 1: they just pour that in. Then they steal it up,
• 11:28
  Speaker 1: and then the same way with the other way. They
• 11:30
  Speaker 1: pump in this liquefied gas and it mixes though this time,
• 11:35
  Speaker 1: right or does it press it down? This is where
• 11:37
  Speaker 1: I got a little confused. So a liquefied guess you said,
• 11:40
  Speaker 1: is um, it's a gas that goes into a liquid
• 11:43
  Speaker 1: state under a certain amount of pressure, right, yeah, okay,
• 11:45
  Speaker 1: so under high pressure. Yeah, so it does mix because
• 11:49
  Speaker 1: it's all liquid in there. Once it gets in there,
• 11:51
  Speaker 1: the whole thing turns liquid, and you keep that pressure
• 11:53
  Speaker 1: up so it doesn't have any room to expand, so
• 11:55
  Speaker 1: it's just in their mix together. And then when you
• 11:59
  Speaker 1: press the nozzle down own and you break the seal
• 12:01
  Speaker 1: as it were, um, the you form a channel with
• 12:05
  Speaker 1: the outside air and the inside air. That change in
• 12:07
  Speaker 1: pressure converts some of that propellant into gas, and it
• 12:11
  Speaker 1: does the same thing is that standard can. The gas
• 12:14
  Speaker 1: presses down forces the liquid up, but some of that
• 12:18
  Speaker 1: propellant is still in liquid form mixed with the product,
• 12:21
  Speaker 1: and as it goes out, it evaporates, it turns into gas,
• 12:26
  Speaker 1: and it also kind of um, it turns that liquid
• 12:30
  Speaker 1: product into a finer miss. Yeah. But what I don't
• 12:32
  Speaker 1: get is is that it actually boils in the liquid
• 12:35
  Speaker 1: gas system. It's like, once you relieve that pressure, it
• 12:39
  Speaker 1: starts to boil, and that's what does it. That's what
• 12:41
  Speaker 1: I was a little confused about. Yeah, I have a
• 12:43
  Speaker 1: feeling that this is a different part of fluid dynamics,
• 12:48
  Speaker 1: that it's not necessarily the boiling point, although it could be,
• 12:51
  Speaker 1: because I don't think any average gas turns into a
• 12:54
  Speaker 1: liquid under under all under pressure. There's just certain kinds
• 12:59
  Speaker 1: that do. I think. Okay, so I think, what's your question, Well,
• 13:04
  Speaker 1: it's actually boiling in the second in the in the
• 13:06
  Speaker 1: liquid gas type of aerosoli, at the very least, it's
• 13:09
  Speaker 1: converting into a gassy estate because of the release of pressure, right,
• 13:13
  Speaker 1: all right? And why did they can sometimes get cold?
• 13:15
  Speaker 1: Did you figure that out? Okay? Boy, there's some guts.
• 13:18
  Speaker 1: There's some people in chemistry lab right now that are
• 13:21
  Speaker 1: just like, oh my god, you guys, I thought we
• 13:25
  Speaker 1: had this one, man. I think we had we do
• 13:27
  Speaker 1: I had it, and I could have done a tap
• 13:28
  Speaker 1: dance doing this earlier, and now it's like, but wait,
• 13:31
  Speaker 1: let me complicate it a little more. Now, I think
• 13:33
  Speaker 1: it's I think the message got through. Um. If in
• 13:36
  Speaker 1: the case of paint, sometimes you need a little help
• 13:39
  Speaker 1: mixing these things together. So that's why a paint can,
• 13:42
  Speaker 1: spray paint can will have the little metal ball bearing
• 13:45
  Speaker 1: on the inside, right, because you actually do want to
• 13:47
  Speaker 1: mix the propellant and the product together in a liquefied can,
• 13:52
  Speaker 1: liquefied gas can, right, because it helps atomize it. As
• 13:57
  Speaker 1: you said, that's very pleasant, exact. Um, what about the
• 14:02
  Speaker 1: rounded bottom of this very can you know why that's
• 14:05
  Speaker 1: that way? If it was flat, it's so pressurized, it
• 14:08
  Speaker 1: could be a bad scene. It could actually go the
• 14:11
  Speaker 1: other way. And everyone knows if you studied architecture, that
• 14:15
  Speaker 1: a dome is more structurally sound than just a flat surface.
• 14:19
  Speaker 1: So that's basically the same concept at play. So that's
• 14:22
  Speaker 1: one reason, Um, it's to protect the integrity of the can.
• 14:26
  Speaker 1: And the second one is is so you can help
• 14:29
  Speaker 1: get all of the product out, because if it was flat,
• 14:32
  Speaker 1: it's like when you're down at the bottom of your
• 14:34
  Speaker 1: of your soda cup with your straw and you're making
• 14:37
  Speaker 1: that terrible little noise and you're tilting the cup and
• 14:40
  Speaker 1: trying to stick the straw on the little corner where
• 14:42
  Speaker 1: it meets the edge. This does it for you. If
• 14:44
  Speaker 1: it's a rounded bottom, it just puts all the product
• 14:46
  Speaker 1: there at the edge and that's where the little tube is,
• 14:49
  Speaker 1: and so you're all set. Yeah, And did you know
• 14:52
  Speaker 1: there's about nineteen billion steel and aluminum cans that include
• 14:55
  Speaker 1: aerosols and other products that are recycled every year and
• 14:58
  Speaker 1: that's equal to enough to build twenty golden gate bridges. Wow,
• 15:04
  Speaker 1: isn't that amazing? So we mentioned there's a variety of
• 15:07
  Speaker 1: different products that you can have that you're trying to
• 15:11
  Speaker 1: get out of your can, from foam to like whipped
• 15:13
  Speaker 1: cream to a bug spray, stuff like that hair spray,
• 15:17
  Speaker 1: although does anyone still use aerosol hair spray? I think
• 15:20
  Speaker 1: some people do, is it? Remember? Do you remember the
• 15:24
  Speaker 1: Bizarre Ways to Die episode? The deodorant boy asol deodorant
• 15:29
  Speaker 1: that he died totally man, that was a long time ago. Um.
• 15:33
  Speaker 1: So the way they accomplished this though with a different product,
• 15:35
  Speaker 1: um is you can have a variety of consistencies. And
• 15:39
  Speaker 1: what they do is they just play with, UM, the
• 15:42
  Speaker 1: ratio propellant to product. Maybe maybe the chemical makeup of
• 15:46
  Speaker 1: the propellant the product have to be just right. Maybe
• 15:48
  Speaker 1: the pressure of the propellant has to be a little
• 15:50
  Speaker 1: different depending on what kind of product you're working with.
• 15:53
  Speaker 1: And then um, the size and shape of the valve system.
• 15:57
  Speaker 1: Like in the case of a fix, the flat that
• 15:59
  Speaker 1: you put in your higher it's not the same as
• 16:01
  Speaker 1: you know, a spray can. It's not atomizing. It's got
• 16:04
  Speaker 1: like the tube hooked up and it's Uh. If you've
• 16:07
  Speaker 1: ever sprayed that stuff in your house, like the Philip Crack,
• 16:10
  Speaker 1: like a whole can of it, It's amazing how much
• 16:12
  Speaker 1: stuff is packed in there. Like when it gets out,
• 16:15
  Speaker 1: you're just like wow, it's like the clown car of
• 16:17
  Speaker 1: the industrial engineering scene. Um, do you want to know
• 16:22
  Speaker 1: a little bit about CFC's chlorofluora carbons. Yeah, I didn't
• 16:25
  Speaker 1: get a chance to look into this, but I'm glad
• 16:27
  Speaker 1: you did so. Prior to the late twenties, there was
• 16:31
  Speaker 1: people were using ammonia and refrigerators and dying from ammonia leaks,
• 16:36
  Speaker 1: and it was just a bad scene. And so everybody said, well,
• 16:39
  Speaker 1: we've got to figure out some sort of toxic, non
• 16:41
  Speaker 1: toxic chemical that we can use as a refrigerant, and
• 16:45
  Speaker 1: a general motors engineer of all people came up with
• 16:48
  Speaker 1: what du Pont later turned into free on, a chlorofluora
• 16:53
  Speaker 1: carbon which supposedly was non toxic. It was. It basically
• 16:56
  Speaker 1: changed everything. Um it was much less harm harmful compared
• 17:01
  Speaker 1: to like ammonia. UM. It allowed us to make cheap refrigerators,
• 17:06
  Speaker 1: car A C, A C window units, like all those
• 17:10
  Speaker 1: things came from the advent of chlorofluora carbons, right, And
• 17:14
  Speaker 1: it was also very ubiquitous as a propellant in aerosol
• 17:17
  Speaker 1: can sprays. Well. I think that's why everyone, you know
• 17:21
  Speaker 1: quit using aquinette, right, because everybody was going in the
• 17:25
  Speaker 1: spraying these things, and they were going up in the atmosphere,
• 17:28
  Speaker 1: and everyone was like, look at them. Go it's cool.
• 17:29
  Speaker 1: They're like, you know, innert, non toxic chemicals going up
• 17:34
  Speaker 1: in the atmosphere, but we're all getting cancer. The problem
• 17:36
  Speaker 1: is when a CFC enters the atmosphere and gets high
• 17:40
  Speaker 1: enough and it's exposed to UV radiation, it breaks down
• 17:44
  Speaker 1: and into its constituting components, one of which is chlorine,
• 17:48
  Speaker 1: chlorine reeks, havoc on the ozone layer. One atom of
• 17:52
  Speaker 1: chlorine can destroy about a hundred thousand ozone molecules, and
• 17:56
  Speaker 1: we need those molecules. The ozone layer protects us from
• 17:59
  Speaker 1: UVB ray from the sun, which are they kind of
• 18:01
  Speaker 1: give you skin cancer and destroyed crops. So in nineteen
• 18:04
  Speaker 1: seventy four some scientists realized that CFCs were doing this
• 18:07
  Speaker 1: in the ozone layer and is gonna be big trouble.
• 18:11
  Speaker 1: And then in the eighties we figured out that there's
• 18:13
  Speaker 1: a hole in the ozone layer over the Arctic. So, uh,
• 18:17
  Speaker 1: a bunch of countries I think seventies signed on to
• 18:21
  Speaker 1: basically outlaw CFC production. Yeah, and then later on another
• 18:26
  Speaker 1: like hundred and twenty I think signed another treaty. So
• 18:30
  Speaker 1: it's very very difficult to find CFC's these days. But
• 18:34
  Speaker 1: they're still around, are they. Yeah? They still use them
• 18:37
  Speaker 1: in some um nasal sprays UM and they're also used
• 18:41
  Speaker 1: in halan, which is a fire extinguisher for airplanes. Did
• 18:47
  Speaker 1: they not still use free on? No? I don't believe. So, Okay, Yeah,
• 18:51
  Speaker 1: it's basically like we did away with those. It's gonna
• 18:53
  Speaker 1: take a while to repair. But they found that the
• 18:55
  Speaker 1: ozone layers no longer growing the hole in the ozon
• 18:58
  Speaker 1: layers growing, it's just holding steady and hopefully patching itself
• 19:02
  Speaker 1: back up. They just forced people to go out and
• 19:04
  Speaker 1: be innovative and find different ways to do these things exactly.
• 19:07
  Speaker 1: And if you compare your airsol can propellant today to
• 19:11
  Speaker 1: one that had CFCs before, you're not going to notice
• 19:13
  Speaker 1: the least bit different. So that's canna aquinit that looks
• 19:17
  Speaker 1: exactly the same as it did in nineteen seven is
• 19:20
  Speaker 1: no longer dangerous, not to the ozone layer. It is
• 19:24
  Speaker 1: the spiders though, if you have a lighter. Yeah, don't
• 19:28
  Speaker 1: ever do that. Kids. Ah, that's it for airsol cans
• 19:32
  Speaker 1: unless you have like another ten minutes on it. Uh No,
• 19:35
  Speaker 1: that's all I got. I mean, what else is there?
• 19:37
  Speaker 1: I genuinely looked in There is nothing else. Ye, go
• 19:41
  Speaker 1: out and do some graffiti, That's what I say. Um
• 19:44
  Speaker 1: artful graffiti though, don't tagg and stuff. You should probably
• 19:47
  Speaker 1: practice at home first. I hate that. Just stupid. Yeah, Like,
• 19:51
  Speaker 1: educate yourself on different types of nozzles, like practice, don't
• 19:55
  Speaker 1: do don't be a punk, agreed, be an artiste. Uh.
• 19:59
  Speaker 1: If you we want to learn more about aerosols, or
• 20:01
  Speaker 1: at the very least, want to see the article where
• 20:03
  Speaker 1: we told you everything there is to know about aerosolis.
• 20:05
  Speaker 1: You can type that word A E R O S
• 20:08
  Speaker 1: O L S into the search bar how stuffworks dot
• 20:10
  Speaker 1: com and that will bring it up. And I said
• 20:13
  Speaker 1: the search bar, which means it's time for message break
• 20:23
  Speaker 1: and now it's time for listener mail. I thought you
• 20:25
  Speaker 1: might say it, okay, Josh, listener mail time. UM, I'm
• 20:30
  Speaker 1: gonna call this uh police sketch eye witnessed stuff. It's
• 20:35
  Speaker 1: from Terry Bennett. Um, Hey, guys, uh listen to the
• 20:39
  Speaker 1: police Sketch episode, and wanted to share my story. I
• 20:41
  Speaker 1: was robbed when I was a teller of a bank
• 20:43
  Speaker 1: in n and at that time, bank robbery was a
• 20:46
  Speaker 1: federal crime, probably still is. I was immediately taken into
• 20:50
  Speaker 1: the back room of the vault and the FBI was
• 20:53
  Speaker 1: called in. When they arrived, a sketch artist brought a
• 20:55
  Speaker 1: large binder, not full of women, but full of pictures.
• 20:59
  Speaker 1: They aces and eyes and noses and mouths, et cetera.
• 21:04
  Speaker 1: Transparencies of face shapes were the base, and the rest
• 21:07
  Speaker 1: of the face was built on the base, one eye
• 21:10
  Speaker 1: and nose at a time. UM I was not allowed
• 21:12
  Speaker 1: to talk to anyone, including the staff of my bank,
• 21:15
  Speaker 1: until I talked to the FBI. I was instructed to
• 21:17
  Speaker 1: write everything I could remember about the robber and the
• 21:19
  Speaker 1: robbery before talking to anybody else. In those days, of course,
• 21:23
  Speaker 1: we did not have digital cameras in the film had
• 21:25
  Speaker 1: to be sent out for processing. Um, all of it
• 21:28
  Speaker 1: in those days. I mean, it's the same like seven
• 21:32
  Speaker 1: years ago. Um. Actually when did digital come around? The
• 21:37
  Speaker 1: early two thousands? Seems like it became. I guess it's
• 21:39
  Speaker 1: more than seven three years on. So uh. The pictures
• 21:45
  Speaker 1: took a couple of days to get back, and my
• 21:47
  Speaker 1: composite drawing was posted in the paper, and my robber
• 21:50
  Speaker 1: was actually caught a couple of days afterward at a
• 21:53
  Speaker 1: methodon clinic in town. When the film was developed, the
• 21:56
  Speaker 1: side by side pictures were incredibly closed. So she did
• 21:59
  Speaker 1: for good job. Sounds like, by the way he was
• 22:02
  Speaker 1: caught using my composite and not the true picture. We're
• 22:07
  Speaker 1: pretty cool. Yeah, it's very cool. We were trained to
• 22:09
  Speaker 1: observe all these details and also to watch for the
• 22:12
  Speaker 1: six ft mark as the robber left the building. And
• 22:14
  Speaker 1: you talked about the call it stores. Yeah, Um, I
• 22:17
  Speaker 1: guess I visit banks. Luckily, even though I was only
• 22:19
  Speaker 1: twenty years old, the training had taken a hold gave
• 22:23
  Speaker 1: me great resources to catch this guy. And to this day,
• 22:25
  Speaker 1: I always observed shady or odd things in everyday life,
• 22:29
  Speaker 1: including license plates like you talked about. By the way,
• 22:32
  Speaker 1: my robber had robbed eight other banks up and down
• 22:34
  Speaker 1: the coast in California. And I got to be a
• 22:36
  Speaker 1: hero for a minute. And that is Terry Bennett. And
• 22:39
  Speaker 1: that's a cool story. Yeah, that's very cool, Terry. Um,
• 22:43
  Speaker 1: thanks for Sharon. I bet she just eyeballs everybody, right, Yeah,
• 22:46
  Speaker 1: she said that like a weird lady. Now she takes
• 22:48
  Speaker 1: out methodon clinics. Yeah, what are you doing? Just getting
• 22:52
  Speaker 1: the methodone. If you want to give us a story,
• 22:55
  Speaker 1: we love our stories. Um, you can tweet very very
• 22:59
  Speaker 1: very short story to us at s y s K podcast.
• 23:02
  Speaker 1: That's our Twitter handle. You can post one on Facebook
• 23:05
  Speaker 1: dot com slash Stuff you Should Know. You can send
• 23:07
  Speaker 1: in an email to Stuff Podcast at Discovery dot com
• 23:11
  Speaker 1: and you can't really tell us a story, but you
• 23:13
  Speaker 1: can hang out with us at our home on the web.
• 23:16
  Speaker 1: Stuff you should Know dot com for more on this
• 23:24
  Speaker 1: and thousands of other topics. Is it how stuff works
• 23:26
  Speaker 1: dot com. This episode of Stuff You Should Know is
• 23:35
  Speaker 1: brought to you by audible dot com.