SciShow Tangents - Glue

Episode Date: May 14, 2024

Humanity is bound together by so many qualities, and in this episode, we add Being Goopy to the list. What does that have to do with glue? A whole lot, it turns out - cue some ominous foreshadowing....Memento goopy! SciShow Tangents is on YouTube! Go to www.youtube.com/scishowtangents to check out this episode with the added bonus of seeing our faces! Head to www.patreon.com/SciShowTangents to find out how you can help support SciShow Tangents, and see all the cool perks you’ll get in return, like bonus episodes and a monthly newsletter! A big thank you to Patreon subscribers Garth Riley and Glenn Trewitt for helping to make the show possible!And go to https://store.dftba.com/collections/scishow-tangents to buy some great Tangents merch!Follow us on Twitter @SciShowTangents, where we’ll tweet out topics for upcoming episodes and you can ask the science couch questions! [Secret Ingredient]Fibers mixed with water to make adhesive https://academic.oup.com/pnasnexus/article/1/1/pgac026/6549457https://www.eurekalert.org/news-releases/945194Adhesive inspired by animal proteinhttps://www.eurekalert.org/news-releases/945194https://pubs.acs.org/doi/10.1021/jacs.1c10936Chinese bricks made with gluey substancehttps://www.atlasobscura.com/articles/chinese-architecturehttps://onlinelibrary.wiley.com/doi/full/10.1002/eem2.12143[Trivia Question]Year that the first adhesive stamp Penny Black was mailedhttps://www.sothebys.com/en/articles/how-a-single-postage-stamp-birthed-the-information-agehttps://www.smithsonianmag.com/smart-news/first-piece-of-mail-sent-using-a-stamp-auction-180983619/https://www.smithsonianmag.com/arts-culture/the-story-of-the-first-postage-stamp-14931961/[Fact Off]Reversible glue made with caffeic acid exposed to certain UV light wavelengths Blood albumin glue used in plywood and pre-plastic resin objectshttps://extension.purdue.edu/extmedia/FNR/FNR-154.pdfhttps://foodeng.wisc.edu/images/publications/2010-9.pdfhttps://asmedigitalcollection.asme.org/fluidsengineering/article-abstract/54/11/15/1162589/Blood-Albumin-and-the-Woodworking-Industry?redirectedFrom=PDFhttps://plastiquarian.com/?page_id=14216[Ask the Science Couch]How glue adhesion/cohesion works and why glue (sometimes) doesn’t cure in the bottlehttps://pubs.acs.org/doi/10.1021/acs.macromol.1c01182#https://www.uhu.com/en-en/glue-advice/adhesive-typeshttps://d-lab.mit.edu/sites/default/files/inline-files/D-Lab_Learn-It_Adhesives_Jul13.pdfhttps://www.sciencedirect.com/science/article/abs/pii/S0143749618300575https://goldbook.iupac.org/terms/view/CT07137[Butt One More Thing]Fibrin glue used to help seal anal fistulashttps://pubmed.ncbi.nlm.nih.gov/12682544/https://pubmed.ncbi.nlm.nih.gov/1782483/

INTRO MUSIC Hello and welcome to SciShow Tangents, the lightly competitive science knowledge showcase. I'm your host, Hank Green. And joining me this week, as always, is science expert and Forbes 30 under 30 education luminary, Sarri Riley. Hello. And our resident everyman, the incredible Sam Schultz. I don't deserve the incredible.

Who wrote the incredible? I'm just a man. Did you write incredible? Or did Sam write it? Do you think I would write that about myself? I don't know. Sometimes you're like, I'd like to be recognized. I would, but... Sometimes you have to, I like I'd like to be recognized. I would, but... Sometimes you have to feel a little bit like Bruce Banner. Yes, incredible. Yeah, Bruce Banner was the incredible one, Sari. Have you ever read a comic book in your life?

Yeah, I got it right this time. The Hulk was incredible. In comparison, Bruce Banner, not incredible. Oh. All right. There's something I'd like to ask you to if when you got exposed to gamma radiation you became a giant green monster When you got angry, what would your name be? Would you be what would do the superlative before Hulk be because we all be hulks obviously Incredible Hulk is taken. So what would what kind of Hulk would you be? Hmm.

I don't know enough words. I think Sam might be the adorable Hulk. Oh, I would like to be the adorable Hulk. Just a little guy who's a big guy. I'll still fight you, but come on. He's just a little guy who's a big guy. That's what it says. Big bold letters on the cover of my comic book.

I think I could go somewhere with that. I guess I'm just naming all of you, because I think Sari would be the amicable Hulk. Oh, yes. Yeah, I'd be like, oh, I'm so sorry. Sari would never even turn into the Hulk, because she'd be like, I understand why you feel that way, villain. I'm not able to be angry. The incapable Hulk.

The incapable Hulk. Just normal, just a normal girl. That's what her comic would say. Hank, what would you be? I don't know, you guys. I gave away all the good ones. I'm really bad at this. I wish I wasn't know, you guys. I gave away all the good ones. I'm really bad at this. I wish I wasn't.

That adjectives? Yeah. Well, yeah, I just want to end up with something that ends in able, which there's a lot of, because I don't think I'd be like the forgettable Hulk. No, opposite of that. Going to rhyme zone. For able? Yeah.

How about the insufferable Hulk? I think that might be right. He tweeted one too many times. Yeah, how about the insufferable Hulk? He tweeted one too many times Okay every week Be meaner to me every week. You said it about yourself. I know but that you said he treated you all agreed with me Let's just say no. no, Hank. No, no. You are the, um, the applaudable hoax. Every week here on SciShow Tantrum, we get together to try to one-up a maze and delight

each other with science facts while also trying to stay on topic and failing. Our panelists are playing for glory and for Hank bucks, which I will be awarding as we play. And then one of them at the end of the episode will win, and I get to have that for the rest of the week. But before we get to all of that, we've got to introduce this week's topic with a traditional science poem this week from Sari. When you have two things to stick together, like a jacket and patch or a cup and a feather, you begin with the question, what tools should I use? A needle

and thread or some nails and screws? Wrap them with rope and tie some knots? Weld them together with that blowtorch you bought. There's staples or buttonholes or perhaps you might choose a tape stick or bottle of mighty fine glues. Take a rock and a stick and some sap from a tree? Then you've got an axe and can chop through debris. Or mix flour and water and you've got a way to mache some paper or whatever they say. And of course there's that aisle of the hardware store with rubber cement and epoxy galore. Adhesives that you can squeeze or spray, each with a purpose like joining rubber to clay. So if you want to avoid a big sticky mess, please read the label and be careful, I guess.

Wow, my shea some paper really good. So the topic for this week is glue. But before we dive in, we're gonna take a short break and then we'll be back to figure out what is even glue? What is even glue? What is even glue? What is even glue? What is even glue? What is even glue? What is even glue?

What is even glue? What is even glue? What is even glue? What is even glue? What is even glue? What is even glue? What is even glue? Oh, gosh, you know, I feel like such a catch all to me that it's just like, there's not even, you know, worth defining. No one's even trying. Yeah.

Well, it's like sticky, but you use it for stickiness because some things are sticky, but aren't glue. Yeah, because they're just snails. But I think you could use a snail as glue, but a snail is not always glue. You know what I'm saying? It's the application of the thing that makes it glue. I think that's pretty good. Like, you use it, you want to stick things together. And what do you use to stick those things together? Probably glue. Yeah. I mean, there's other ways. You could weld.

But when you're welding, aren't you using, aren't you like melting something into a goo that then dries into hardness? So is that, is that the the is the glue? Is there a momentary glue there? Is solder glue? I don't know. Is solder solder is just lead, right? Solder is how it's spelled. Solder. Yeah, that's right. A low melting alloy. I think solder is solder. OK.

And glue is the rest of the sticky stuff. I don't know why. I don't know why solder is... Because like, if you gave me a glue and you said in order to get this glue to work, you have to heat it up almost as if it is a hot glue that comes out of a hot glue gun. And I wouldn't say, no, that's just plastic. I'd say that's glue. A soldering iron is a hot glue gun. A soldering iron is a hot glue gun with metal that comes out of it.

Yeah. Welders are just crafting. Yeah, I mean, glues can be a lot of things. If you look back in history, nowadays we've got lots of different glues that are a lot of plastic-based, but there's glue on tape and sticky notes, like that's a kind of glue. Those are just like pressure sensitive glues. I guess the more general term for glue is adhesive. So if you see the word adhesive, it's also a glue probably.

That opens it up to a lot of stuff I feel like maybe doesn't count. Like I wouldn't have thought to look up for this episode, such as tape. But tape has glue on it, I guess. Tape has glue on it. Part of tape is not the glue, which is the plasticky part on the outside that isn't sticky. So the non-sticky plastic is not glue, but the sticky plastic is glue. And I think glue has something to do. So we did an episode on sticky things where I basically just talked about glue in the

definition section, I think. Because the sciency part, if you want to start getting into the chemistry, which we also don't really know about glue, but the main things to know are adhesion and cohesion. The two hesions, they come up in all kinds of sticky conversations. So adhesion is when you stick two different things together. So if you were gluing a patch to a jean jacket, those are, you want the glue to stick to the jacket, you want the glue to stick to the patch, you want the glue to stick to the jean, and that helps adhere the surfaces together. Then there's cohesion,

which is the same thing sticking together. You want the glue molecules to stay stuck to themselves. You don't want them to slip past each other. You need them to clump together, harden up, get sticky. And so when glue doesn't work, it's usually a failure of one of those points. It's either a failure of adhesion, the glue peels away from the surface

you're trying to stick it to. It's a failure of cohesion, which means the glue molecules didn't set up properly. So the glue is just like still runny or sticky. Or a substrate failure like the jacket melts when you put glue on it because you didn't read the label and then you put the bad glue on the jacket. Have we ever been in a situation where the glue succeeded in holding the thing in place

but the thing that was being held in place itself just ripped away? As I've done that, but I've done that with wall. Oh I've ripped big chunks out of the SciShow studio walls before. Yeah I believe that. Sometimes the glue is stronger than the thing holding the glue. For example, also anytime I've ever gotten super glue on my fingers. Glue is really one of the things that you encounter the most often in your day-to-day life that's like this makes sense that it's sticky and it sticks to stuff and then somebody asks you why it does it and then you're like, Oh, gosh, it's sticky. I don't know.

And then it gets kind of scary. Sticky is almost as weird as like magnets. It's like, wait a second. You mean I can touch this and then I have to keep touching it? Yeah, for a long long time. Can't stop. It boils down to electricity and weird little forces. It shouldn't, though.

It's honey. Yeah, because all kinds of little forces are going on at that level. It's either the glue is seeping into, like the pores on your skin, and then the glue molecules are bonding to each other, and then they're mixing in with your skin molecules a little bit and everything. If you think about it too hard, it gets stressful.

Does it actually bond to my skin? molecules a little bit and everything. If you think about it too hard, does it actually bond to my skin? Like actual shit, like kind of sharing electrons a little bit. I think it is less common in like household adhesives, like the Elmer's glue is not bonding to your skin and whatnot. But I think when you get to more industrial strength glues that are designed to bond to materials, then yes, it's actually integrating. I mean, super glue feels like it is bonded to my skin.

Super glue becomes sticky and cures due to a reaction with water molecules. So when it is exposed to air, there's water vapor in the air and your skin is moist. And so I bet it is reacting to the water molecules in your skin. So in that way, yes, because you have water in you. Yeah, it's probably getting into the water that's just on the other side of the skin. Yeah. Or like very surface level water, which makes it very sticky. That's right.

One might say super sticky. Yeah. I feel like I know roughly what glue is now. Do we know where the word came from? Cause it's a good one. I agree. It is a great, great, great one. It's a good one.

It is one of those that has stuck around for a while. It comes from the old French glue, which... There you go. There you go. Still there, which meant glue. Or specifically bird lime, which is a way that people used to catch birds. So they used to like mush up...

This sounds fun. Mistletoe berries or other plant sappy things and spread them on the branches of trees and catch birds. And then birds would get stuck. And then you could presumably eat them for meat, collect them for feathers. And it's been used in various forms. There isn't one recipe for bird lime. It's just glue that you use to trap birds on trees in cultures around the world.

I had no idea about bird. I mean, it makes sense that when there's food flying around, you just make something sticky and be like, that's mine now. Like the way that we do with flies, but not for food. One time I had a spider trap in my basement and I put it there, and this was an old house, and I came back like six months later,

and it was just pure spider. So I was like one of those sticky, they get stuck to it spider traps. And I picked it up and it was just pure spider. So I was like one of those sticky, they get stuck to it spider traps. And I picked it up and I was like, oh my God, this is terrible. And then I like, but I was like, but I kind of might want to look at them. So I like kind of got close to it.

And then one of the spiders lunged at me. No, Hank. It was like, whoo. Just. There, yeah. There he is. The evil God who's trapped us here. Only a spider would be like, there he is. The evil god who's trapped us here.

Only a spider would be like, there he is, god, let's get him. I truly saw you as the insufferable Hulk and went, I think I can take him. There's that insufferable Hulk himself. He could totally take me. But before we had the word glue, we had Latin glutinum, which is also related to gluten. So that's where we got that word, which is just any sort of like sticky glue stuff from plants or other things. But the Greek word for glue was kala, which we see in collagen, which is the structural

protein in connective tissue. So we got the word gluten and glutinous from Latin, and we got the word collagen from Greek. But they were all referring back to glue. We had sticky stuff and we needed words to describe it, and they stuck around because glue's a good word. Got sticky stuff from day one. There's sticky stuff everywhere.

Since we were talking, we knew that stuff was sticky, which makes sense because even if we still don't understand the science, we can still go around touching things and say, hey, that's sticky. Yeah, we understand the science well enough to be like, that's sticky. I feel informed. And so now it must be time to move on to the quiz portion of our show. This week, we're going to be playing a little bit of secret ingredient. Humans have been making glue out of all sorts of materials,

which is a testament to both how sticky nature can be and how creative humans are when it comes to trying to get things to stick together. So today we're gonna highlight a few of those ingenious glue recipes. I'll describe some kind of glue past or present minus one key ingredient. You'll have three possible options to choose from. It's up to you to guess what the secret ingredient is. Are you ready? Glue.

Are you a glue Pokemon now? That's how I say yes now, glue. In 2022, researchers published their results designing an adhesive material that could be used in a variety of surfaces including metal, plastic, glass, even biological tissue. This glue involves using water to activate fibers from a source found in nature, which allowed scientists to then shape the fibers into sticky structures for different adhesive purposes.

But what was the source of those fibers? Was it pumpkin or mistletoe or eggs? Do eggs have fibers? I never looked at an egg and was like, that's got fibers in it. Does everything have, does everything sticky have fibers? They have polymers, they have protein. What's a fiber?

You eat fiber, like in plant fibers. It's like a roughage. Like fiber, molecularly, biochemically, is a carbohydrate. It's like a sugar. Okay. And you said the mistletoe thing already. Mistletoe pumpkin both have fiber. Yeah.

Pumpkin, stringy and gooey. That's right. Mistletoe, I think they used it for sticky, for capturing birds. So does that mean this is a trick or does that mean that you just overlapped a little bit here? I don't know. I guess I'll go with pumpkin. They're one of the stickier things, I think, that you could grow on the ground.

I don't love the way I feel after carving a pumpkin. I'm gonna overthink it. Okay, I'm gonna go with mistletoe to try not to overthink it. I bet it's just the egg. That was the correct instinct, Sari. Oh, no. That was good. I mean, you knew about the mistletoe thing, so this is amazing. So mistletoe uses...

It's a parasitic plant, so it uses the substance, the sticky substance called viscine, or visin, that surrounds the seeds to do some stickiness. And when birds eat mistletoe berries, they excrete the seeds along with the sticky viscine, which can then get stuck to the trees and branches where the mistletoe can germinate. Researchers can make up to two meters of these viscine fibers, and the stiffness of the fibers changes with the humidity. More humidity, the fibers become more self-adhesive. So researchers developed a way to process wet viscum fibers and stretch them into either a film or into 3D structures,

creating an adhesive structure that could potentially be used to like even seal up wounds. Hmm. Cool. And bird poops on your wound and it closes up. Is that how it works? Don't put bird poop in your wounds. We're not doctors here at social attendance, But I don't think that's allowed. Round number two. Sometimes taking inspiration from nature leads researchers to actually improving upon it. For example, another group of scientists in that same year, 2022, developed an adhesive inspired by protein produced by a particular

animal. But instead of just copying the protein directly, the researchers added smaller units of the protein to a synthetic polymer and found that it actually performed better as an adhesive compared to the original protein. But what animal was it? Was it mussels or frogs or barnacles? None of those. I was thinking spider. But I guess there are a lot of sticky animals. They're always doing stuff with spiders when you search for glue news. A lot of spider stuff. I think I did see some mussel stuff too though, so I'm gonna say mussels. I feel like there's news about all of this stuff. Oh, but they're not the ones that stick to stuff.

Do mussels stick to stuff? Yeah. They attach themselves to like an underwater pillar, like a dock. Barnacles do too. Okay. There was an episode of Tangents where I talked about frogs that glued themselves to each other to have sex. It was like early, early Tangents.

But I think that was a couple of years ago. So old news, not 2022. I'm over, I'm gonna go barnacle. I'm gonna go barnacle. Well, muscles stick to rocks using a strong adhesive protein that's found in their foot and a number of researchers have been looking at muscle slime to figure out ways to turn it into adhesive for various applications. This is also true for barnacles, but in this case, this was a muscle thing.

So the proteins found in the muscle slime, they have these long linear chains of amino acids that belong to a broader class of sequences called tandem repeat proteins, basically made of repeats of a given amino acid sequence. Other sticky materials like spider silk are also tandem repeat proteins. And while scientists know the sequence of these proteins, re-killing their overall structure can be super complicated.

So this group of scientists decided to look instead at something called protein-like polymers. Instead of trying to reconstruct the original protein out of the repeating units, they took individual units and added them to that synthetic polymer and tested how good it was. And it was even stronger than the muscle proteins. Wow.

Like every animal in the world's really good at making sticky goop. How come? I don't know if every animal... We like all rule at it. Yeah, I mean, in general, one thing you can say is that we're pretty goopy. Every single one of us is goopy. That's what unites us all and across this planet.

I think this is the new memento mori. It's memento goopy. Remember, we all goop. That's the more positive one. You don't have to die first before that. Yeah, you just get to, yeah. But you do have to be goop the whole time. You do, yeah. Inside me, I have lots of goop.

So that is not a problem. It's weird to be a big goop, you guys. Do you ever feel like it's both sort of an element of freedom from all of the stress of day to day life, but also just a terrible, a terrible weight of its own to carry around that was just a bunch of goop that has anxiety? I mostly think it's really bad because it's always trying to come out of view. Right.

The goop in particular would be great if you could just. I don't want anybody to see it. I would like the goop to just give me one freaking day of my life, please. To live and not be goopy. And I'm just barely held together by like my bones and the structural tissue in here. Otherwise, take those out full goo. Yeah, go just up. Yeah. Not even like composed like a slug. I don't have that tightness in me without my bones.

I would be a mess. You don't have that tightness of a slug, you know, really considered one of the tighter animals. Yeah, you look at a slug and you're like, damn, that's a tiny animal. Yeah. All right. Round number three,

while the previous two rounds might have you thinking that 2022 was some particularly good year for glue, the truth is that humans have been making glue for a long time. And in China, researchers have been studying old bricks, including one from a 2000 year old tomb from various locations to understand how they were made. Some of these very strong bricks were made by mixing sand and lime, which came from heated limestone, with a particular substance that glued everything together. What was the secret ingredient? Was it sticky rice, bamboo, or volcanic ash?

Is this one we've done? Have we talked about this before, Sari? I think it might be. You were trying to act so normal. Her face was like... I've been told I do not have a good poker face at all. No, you're about five pixels on my computer screen right now. And you're the size of a postage stamp. And you still are like, Sari's my computer screen right now. You're a size of a postage stamp I remember correctly and you're about to answer before me to totally give it away I know that's what you're about to do wasn't that the answer is sticky rice. I think

Remembering correctly The answer is sticky rice, I think, if I'm remembering correctly. I think it's sticky rice too. I think I talked about this in a different... We just talked about goo a lot. I think I got to you. I think you like to talk about goo. I think you like to keep it all straight. I mean, like, eventually we're going to have to forget all of the stuff that we learned

in this podcast, right? This is a greatest hits episode. So yeah, sticky rice. Isn't that cool? The thing is that it's so cool. It is really cool. It is extremely cool. Like who thought, oh, let's take some food and put it in. Food can be sticky too. It's sticky. So it makes for good brick binders, thanks to something called amylopectin, which is a polymer with these long branching chains.

They're probably up to grip onto other surfaces and components inside of the brick. It makes sense. It's almost like putting rebar inside of concrete. It's like you have this other thing that is providing structure in a different way, and that means that it can then be strong in a different way. Though I will say that volcanic ash was a popular ingredient in concrete in other countries, but it was not readily available for use in China. To all the people out there who hadn't known about the sticky rice and maybe were thinking

about volcanic ash. All right, well, it's a tie ball game, everybody. We're gonna take a little short break right now, and then we'll be back. For the tiebreaker, it's gonna be the Fact Off. Welcome back, everybody! Now get ready for the Fact Off! Our panelists have all brought science facts to present in an attempt to blow my mind.

And after they have presented their facts, I will judge the most mind-blowing one and give it the wind. But to decide who goes first, I have a trivia question. This year, Sotheby's put up a letter known as the May 2 Penny Black for auction. One of its notable features was its stamp, known as the Penny Black. The stamp featured an image of Queen Victoria and on its back was gum Arabic, which helped stick the stamp to the envelope, making the Penny Black the first adhesive stamp to be used in a public postage system. In what year was this letter sent? When did mail happen? When did, when we were like...

You're gonna have to guess. Ugh. I feel like a lot of these social services kind of happened later than you think they would. I don't remember what's making me think that, but a previous episode of Tangents, I was like, whoa, that didn't happen till then? And I can't remember what it was,

but maybe like, do you think Shakespeare was mailing stuff? Not with a stamp, not with a postage stamp. Yeah, not with a system. There was a person just like hiring children on the street probably. Doesn't matter, cause I don't know what year Shakespeare's from. I think it happened in 1850.

I think early 1900, I think like 19, right before the World War. So 1910 or so. Indeed, it was 1840, Sam. Before this, the postage system worked by having the postage people arrive with the mail and say, here's your mail. Here's how much it costs to get it. And a lot of times people will be like, no.

And that was a lot of extra trouble that they weren't getting paid for. So they're like, not deliver the mail. And so they were like, now the person sending the mail should pay for it. And that way the person receiving it just gets it for free. Which I mean, I guess it does make more sense. But also it's like, I'm the one getting the thing.

Yeah, but you could really ruin somebody's life by mailing them so much stuff, don't you think? It's just like, I have to keep saying no. There was this thing, I don't know if it still exists, but when I was a kid you could get stuff's COD. Cash on delivery. Cash on delivery. Yeah, I feel like I lived through the like,

no cash on delivery at the end of like infomercials and stuff age, so that must've been when people were putting their foot down. I remember I sent something, I sent a Magic the gathering card cash on delivery once when I was, I would sell magic cards on Compusurf. What a cool story. That's a word for it, Sam. What a cool sentence you just said.

What an extraordinarily hip and not at all nerdy sentence that that was. And also that means that you get to go first. All right. Gluing stuff together is typically a one way process. Things aren't glued together, then you put glue on them, and you mush them into each other, then they are glued together for all of time sometimes.

And that's handy in some ways, like for instance, if you just really need two things to be stuck together and are pretty sure that you're never going to change your mind about that. But where is the glue for us indecisive people or for those of us who feel a lot of pressure when we're making a collage in a digital world where nothing is permanent? We demand a glue that isn't permanent either. Luckily for us,

a team of researchers out of Japan's National Institute for Material Science developed just such a glue in 2023. This glue isn't very glue-like under normal circumstances. It's not sticky. It doesn't dry when exposed to air. Two things you don't really want in your glue. But this non-sticky goop has a special ingredient, caffaic acid, I think that's how you say that, a compound found in a lot of plants, including coffee beans and, all right, now this is chemistry, which I actually did get a D in in high school.

But cafeic acid contains within it acrylic, is that a possibility? And under certain circumstances, it can take on the properties of acrylic, as in it can become quite plasticky. And the certain circumstances that make Caffeic Acid plasticky is exposure to a specific wavelength of UV light. So back to this glue that is not sticky.

When it is time for it to do its thing and get sticky and stick stuff together, it is painted onto the objects to be stuck together, hit with UV radiation, and it instantly hardens into an insoluble, insoluble, plastic-y substance, and bonds those objects together. And the bond it makes is really strong too. In one test, they used it to suspend a 40 kilogram weight for three days straight, and it showed no signs of breaking.

And then they used it to seal cracks in some pipes and Then they pumped high-pressure water through the pipes and so that didn't break and it's waterproof And I haven't forgotten about the thesis statement of my fact Which is that indecisive people need an indecisive glue? Well, if you expose the glue and it's hardened state to a different wavelength of UV light It reverts back to non sticky goop form Which can then be collected and used again later, hit with the UV light, turned hard again.

So right now this glue is being put to the test in various applications, but one day, if this is ever available to consumers, the agony and anxiety of gluing something to something else will be no more. That's very interesting. Some people will know that like gel nail polish is this way where it hardens under UV light.

So and that's the same thing. It's like causing it to pull it like the UV radiation is causing it to polymerize. But like the idea of a different wavelength of UV light undoing it also to me seems dangerous. Like is there none of that UV light around? Would it have to be in the shade? That would be bad I guess.

I guess you just wouldn't build like really important things with this glue. Because it'd be pretty easy to sabotage I suppose. To have the right wavelength. I don't know there's lots of UV light. I couldn't find any article that tried to even try to explain how this worked but how would it? I know that like I get how the polymerization would happen. You just like, you need to have certain sites on the monomers, you know,

the individual blocks of the polymer. You'd need to have like some site that would like lose an electron because it got hit to the UV light. And then it's like primed to bind to the same site or a similar site on the other side of another nearby monomer. So breaking that bond is, I guess, UV light is very high energy.

It does a lot. It can fly. It gives you sunburns and stuff. But I am surprised that that is possible, and it's very cool. I just hope that the people from Flex Tape get their hands on it so they can make extra good infomercials about it. That's what I was thinking too. I need a guy screaming at me about this glue.

When you guys were in high school, did you like chemistry? Were you like, I'm good at this and I'm good at doing it. Or was that later? I liked it in high school. Yeah, I was a big nerd. In between selling my Magic the Gathering cards when I was balancinguServe. I was balancing reactions, doing stoichiometry. Yeah, like I would do things. I would like learn chemistry jokes on the internet for fun or things like that.

Oh, God. I hate you so much. Let's use a math joke. How did we end up on a podcast together? You would have bullied me in high school, Sam, I think. I think you would have been like... No, I think Sam would have tried to get you to come out and you wouldn't have to come out.

That's true. I was friends with a lot of people who I helped them with their homework and then they made me marginally cooler. That was me back time. We were, yeah, there was like, we had a ring where it was like, some of us were good at science, some of us were good at history, and we'd all just like pass our homework around before. That doesn't sound like helping each other with your homework so much

as just copying each other's homework. Well, I didn't get any better at science, so I guess you're right. All right, Sarah, what do you got? So when we were talking about the etymology of glue, I mentioned an animal-based substance called collagen, which is from the Greek word for glue, kala, which is a common protein that gives us strength and structure in a variety of our tissues like your skin or bones or tendons. And it was named

because it makes good glue. So some of the science couch questions that we didn't choose asked about horse glue, which I can talk a little bit about here. One of the most common types of animal glue or was because you don't see it very much anymore is hide glue or bone glue, which is made from rendering out the collagen out of animals like horses or cattle or rabbits, really much like the birds that you're catching on the tree. Anything that's around, they die and then you turn them into glue. Gelatin is rendered collagen also, which is why Jell-O isn't vegan, but there are plant-based alternatives to it. And you can make other types of animal glue as well.

Hoof glue or horn glue, where the protein, the structural protein inside is keratin instead of collagen. And if you really don't want to waste any animal parts, you can also make blood albumin glue, where historically they would dry out all the solids from blood, so the cells and the proteins and whatnot. You can mix that powder with water and either calcium oxide which is lime or sodium hydroxide, which is caustic soda, to make a slurry.

And then you use heat and pressure to get those blood proteins to coagulate and harden. And that makes a pretty strong and fairly water resistant glue. I don't know why this is giving me such a hard time, but I hate this. I'm so normal about it, which may be, again, brain. Yeah, weird kid to the max of the three of us. But basically, this blood glue was a precursor to synthetic resins and it was fairly abundant because blood was otherwise a waste product from slaughterhouses and places like that. Oh, I always think that this was made from human blood. that makes way more sense. Oh yeah, animals. As far as I know, I'm sure someone made human glue,

but I don't wanna think too hard about it. Yeah, well, look, blood, you can give up a certain amount, but you're right, we have a ton of blood available, not like humans, not in our bodies, but like as the razors of livestock. Yes, as species who raise other animals. I found two main historical uses for blood glue that felt worth mentioning. Before we had plastics, like the thermosetting resin Bakelite, which was patented in 1907. We've talked about it on the podcast before and used for things like billiard balls

or bracelets or things like that. A French guy named Francois Charles LePage LePage, patented what he called bois d'ercy, which means hardened wood in 1856. And basically what he did, he took animal blood plus sawdust and then a heated pressure mold to produce dense, glossy items

like picture frames or combs or plaques with people's faces etched into them or whatever he can dream up. So instead of using like wood glue or epoxy resin like we would nowadays, he just used blood glue for his arts and crafts, which is very weird. That's cool. Was this very, was this similar to Bakelite? It was like the precursor to it. So I don't know if it directly inspired it, but but yes similar in that it was a thermo setting like it needed heat and pressure

to then harden and solidify into this glossy shape and it looked kind of similar except for darker red brown and then the other main use for blood glue I could find that it was used from at least World War I so the 1910s to the 1930s or so but possibly longer to make it was used from at least World War I, so the 1910s, to the 1930s or so, but possibly longer, to make, it was used to make plywood that was relatively water resistant for all kinds of construction of boats or airplanes or other structures, because that those plant glues or resins weren't as waterproof and this heat compressed blood was. In an age of the problems of microplastics,

let's bring it on back. And I found some of this blood plastic, and it looks pretty good. It looks cool. Yeah. Yeah. There's a bunch of doorknobs, and I'm like, man, if I had a blood plastic doorknob, I think I'd be the most popular kid in town. Everything we own will be blood red,

which is kind of cool in a way. Super good. Just plastic vampires. I think this is fine. will be blood red, which is kind of cool in a way. Super good. Plastic vampires. I think this is fine. You don't have microplastics anymore. You have microblood, and that just degrades. Microblood's fine.

Everybody knows that. That's it. That's all I got. I don't think we use blood glue or many animal glues anymore on industrial scales because plastic is cheaper in the way that plastic has overtaken many industries. We still use animal parts for gelatin. Yes, we still use animal parts for gelatin.

And I'm sure there are people who still make animal glues. Like, I don't want to rule it out completely. There's people who use every piece of the animal, et cetera. But I don't know. I don't know about blood glue. I never heard of it. I never thought about it before. It seems hard. Like, it seems like you'd need specific equipment. That's a lot of pressure to have to squeeze these objects together.

Oh yeah, I want some now. I do too. I hated this and now I'm really into it. Definitely looks like a bunch of stuff Dracula would have in his house. Yeah, for sure. Take a little nibble of his thorn off. That'd be the problem, he'd lick it every once in his house. Yeah, for sure. Take a little nibble of his turn off. That'd be the problem.

You'd like to have a look at them all the time. And be a regular Hansel and Gretel house. Yeah, it's like this. It's like those videos where like something in the room is made of chocolate. So for is this cake? Well, now I'm in trouble because I have to choose between these two very good facts. We've got blood glue, also making objects pre-plastic, and also a reversible glue that uses UV light for the indecisive and anxious.

I think I'm going to give it to Ceri because I got brought on the whole journey. I hated it and then I loved it. I think that's a better fact overall. When the person who brings this back says, I learned about this on a podcast, Sideshow Tangents, and they're winning the Nobel Prize for saving the world, then this will all have been worth it. You know what I want really bad? Is like blood glue, like vinyl record,

or like even like just the case of a cassette tape and you could like listen to some like Nordic death metal on it. That'd be so good. And the thing is, is any you do it with a doctor. We're not doctors. A musician could theoretically, I don't know how much blood you need, but you could like donate, extract some of your blood over time, mix it with some sawdust and press your vinyl records with your own blood, which is very wild to think about.

The ultimate marketing campaign, instead of owning a piece of your hair, you can be like, this was made with my blood. I think that I would purchase fewer plastic bottles if I had to make everyone out of my blood Personal responsibility coming back around And now it's time for ask the science couch where we ask a listener question to our couch of finely honed scientific minds at Matthew Gdos on Twitter asked, why doesn't it stick inside of the bottle?

What a stupid question. Why doesn't it? Matthew, as a friend of ours, so glues are activated by a bunch of different things. So we talked about some of the things that can be activated, UV light, water. Oftentimes there's a solvent that is evaporating and inside of the bottle

the concentration of the solvent is so high that it can't evaporate anymore. So the pressure of the solvent inside of the bottle is keeping it in solution. This is like my bag. That's crazy. Inside of the bottle is different from outside of the bottle is the main thing to know. Did I miss anything, Sarah? main thing to know. Did I miss anything, Sarah? No, I think I just have more details, but that's basically it. The glue manufacturers want it to not stick inside the bottle. And so they've designed the inside of the bottle and

they've designed the glue chemicals to not be sticky there, in many cases. And there are there are different kinds of glues, like you mentioned, the main buckets that I kind of mentally sort them in, there's like non-curing glues. So there's glues that stay sticky, basically, which are sticky notes, tape, things like that, where if you unstick them and re-stick them,

they'll still adhere. The only way that they'll stop, kind of, is if they have too much junk on them, if it's dirty. So there's too much stuff stuck to them already for them to stick to something else. You could even clean them off and they would be sticky again. And so that those those kind of stickies, they're they're non curing, they don't they don't lock into place when they polymerize. And there's curing that doesn't involve a

complex chemical reaction. So a lot of like craft or hobby glues, like Elmer's glue is just water plus the polymer. And when the water evaporates out, the polymer locks into place. And so then that becomes like the glue sticking in place. Or there are, like Hank said, other solvents that are in the glue. So rubber cement, you apply it to both surfaces.

You let it like flash off, which basically means you let the solvents evaporate and then you smoosh the glue together. Wow. And then the glue coheres to itself. That's the cohesion of it. And then there's reactive curing, which are the glues that are in two separate chambers,

kind of a lot of two-part glues are this like reaction curing, where if you just put half of that glue on a surface, it'll never lock up. It'll never stick the two objects together. You need that chemical reaction to form the polymers that form the sticky stuff. And so that glue, the reactive curing glues,

will never stick inside the bottle because they're designed not to. Whereas those non-reactive curing, if they evaporate in some way, like super glue like we mentioned, you need water vapor. So there's no water vapor inside the bottle, but there is outside the bottle.

Once you have a half empty bottle, it might start sticking at the inside of the bottle because then the outside's inside the bottle. And you can't have that if you want your glue to remain liquidy. That's why they sell very small bottles of super glue that are basically single use. Yeah.

Which maybe we wouldn't do if we had to build them out of our blood. We would find a way. Yeah, so basically the like super glue is a reactive glue but they don't have to have the separate chamber because the stuff that would be in the separate chamber is in the environment. Yes.

And there's some weird glues. Another person in the Discord asked about thread lock adhesives or thread lockers, which you put on like a bolt and then you screw the bolt into a nut and then it sticks. And those don't need oxygen to react. They need the metals to react. So specifically those threadlockers say, don't use with plastic because it'll dissolve plastic.

But when those, I think they're made of acrylic, some sort of acrylic compound, they cure when in contact with metal because metal has all these extra electrons around is reactive in certain ways. And those glues polymerize when they're in contact with metal without oxygen which is like very weird. So there's glues for all kinds of situations and that's why a lot of glues like there are all-purpose

glues but a lot of glues are for gluing specific things like Elmer's glue is good for paper because the paper allows the water to evaporate but it's not so good if you are going to like rubbery things together because then the water to evaporate. But it's not so good if you are gluing two like rubbery things together because then the water has nowhere to go. You said glue a lot of times. I did. I heard myself say it and then I saw you laughing. I just kept going. I don't know. Well, if you want to ask the Science Couch your questions, you can follow us on Twitter at SciShow Tangents or check out our YouTube community tab where we will send out topics for upcoming episodes every week, or you can join the SciShow Tangents Patreon and ask us on our Discord.

Thank you to the space say on Discord at rsTurtleness on YouTube and everybody else who asked us your questions for this episode. If you like this show and you want to help us out, you can do that in a bunch of ways. Number one, go to patreon.com slash SciShow Tangents to become a patron. Get access to our bonus episodes and our Minions movie commentary, which, come on. And cars too, and cars too. Also the cars commentary, you can find out what's inside of the cars. We kinda do and it's scary. It's not, it's upsetting.

Shout out to patron Les Aker for their support in particular. Thank you. Second, you can give us a review wherever you listen. That's super helpful and helps us know what you think about the show. And finally, if you want to show your love for SciShow Tangents, just tell the people about us! Thank you for joining us. I've been Hank Green. I've been Sari Reilly. And I've been Sam Schultz. SciShow Tangents is created by all of us and produced by Jess Stempert. Our associate producer is Eve Schmidt. Our editor is Seth Glicksman. Our social media organizer is Julia Buzz Vazio.

Our editorial assistant is Debuki Chakrabarti. Our sound design is by Joseph Toulamedish. Our executive producers are Nicole Sweeney and me, Hank Green. And of course, we couldn't make any of this without our patrons on Patreon. Thank you and remember, the mind is not a vessel to be filled, but a fire to be lighted. [♪ Music & Intro To The End of The Video, by Kevin MacLeod & The CWO plays in the background. But one more thing! Sometimes because of an infection or injury, a very small tube called a fistula can form inside of your body where it does not belong, like in your lungs or blood vessels or even

your anus, causing leaks that you definitely don't want. One way that doctors try to seal up anal fistulas is with fibrin glue, which is a two-part biological adhesive made of two molecules involved in wound healing and clotting. Basically, after treating the infection, doctors squeeze the glue inside the anal fistula to seal it up and let your body heal. I'm very glad that's a thing. I didn't just find out now, but I was upset the first time I found out what a fistula was. It didn't sound like what it was. Yeah, it sounds like it would be a lump or like an infected lump or something, but it is a hole where it doesn't belong, which is very weird and upsetting to think about. That your body can just do that. That your body can break in that way. I feel like, like,

on construction maybe that could happen. Like you could be born with a problem like that. But once I'm set, like I'm built, I shouldn't develop new tubes. We're just goo. We're just goo and we can sometimes get punctured, I guess. Yeah. But from the inside.

The goop top issues.