Get in text technology with tech Stuff from how stuff Works dot com. Hey there, and welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm flying solo today and I'm going to talk about something that I thought was really cool. I actually learned a lot in the process of looking into this. A few weeks ago, I covered a story for How stuff Works Now about a technique to make melted chocolate less viscous so that it flows more freely through manufacturing equipment. So a couple of things.
First of all, How stuff Works Now, if you aren't familiar, is our more news oriented page, So if you go to now dot how stuff works dot com you can see it. We have a lot more stories that are reflective of things that are unfolding now, thus the name, and we also do video for that. There's also a podcast hosted by Lauren Vogelbaum. You can subscribe to that house Stuff Works Now. It's a summary of some of the stories that we cover each week. So if you're
not familiar with that, go check it out. It's pretty awesome. Anyway, I did this story about chocolate and making sure you could reduce the viscosity of liquid chocolate so that it doesn't come up stuff, because one of the challenges of working with chocolate is making sure that it doesn't clog up the pipes like Augustus Gloop in Willy Wonka. So a consulting firm working on behalf of Mars Incorporated, which is giant candy company that makes a lot of different
chocolate products. This consulting firm went to a group of physicists at Temple University, and physicist is one of those words I have difficulty pronouncing. I think I might just say scientists. Scientists at Temple University. Hey, and that's way better. And these guys have developed a method to make crude oil flow more easily through pipes using electric fields. So the question that the consulting firm had was could you do the same thing you did for crude oil for chocolate?
And here's a spoiler alert, Yeah they could. But I want to talk more about what they did and how they did it because it's it's a really interesting, uh story. So I'm gonna go into a bit more detail about the physics and the technology behind the scientists solution for this problem. It's pretty cool, and a lot of it was stuff I had no idea about before I began to research the story. So today's episode is going to
be about chocolate. It's gonna be about viscous fluids, about electro real logical fluids and how an electric field can change their fluid I properties, specifically viscosity. So yeah, this episode is gonna be science heavy, but there's also chocolate, so stick around. You know everyone loves chocolate. So let's get into the physics first. Now, fluid dynamics is be complicated, and also there's some stuff that's related to this that
falls into the category of misinformation about viscosity. So I'll be talking a lot about not just the principles in general, but some specific uh myths that I would like to bust, as some of my former coworkers used to do on a regular basis. So, first of all, viscosity is a property of fluids or semi fluids, and it can be described as a fluids thickness or stickiness and its resistance
to flowing due to internal friction. More accurately, viscosity is a measure of the resistance of a fluids deformation due to tensile or shear stress. Now, sheer stress is mechanical stress that's parallel to the surface of that substance. So, uh, you could think of sheer stress as it's not perpendicular. It's not like an impact, right, It's more of a tearing um ten style stress is a pulling stress rather than a compression stress. So again, instead of compressing stuff
closer together, it's about pulling stuff further apart. And water has a pretty low viscosity. Honey has a very high viscosity. So we actually measure viscosity in units called poises p o I s e s. Water at room temperature twenty degrease celsius or so has a viscosity of zero point zero one poises or a center poise. In other words, a thick oil might have a viscosity of one point zero poise. Now we measure viscosity with a viscometer. I'm not making that up. It's actually the name of the
tool used to measure a fluids viscosity. Now, typically we will call a liquid viscous if its viscosity is higher than that of waters, and if the viscosity is lower than that of waters, because water is not the least viscous material that we know of. If it has a lower of viscousy then water we call that fluid mobile. So some fluids are so viscous that they can actually seem to be a solid, and this leads us to
that misinformation I was talking about. It's one of those things that I hear bandied about pretty well, not not not as frequently as it used to, but it's one of those miss understandings that gets passed around its fact every now and again. And that is the idea that glass is one of these fluids, that glass is actually a fluid that is um so viscous that it appears to be a solid, and that is not true. Glass is not a very, very viscous fluid. It's a little
more complicated than that. Uh So, here's the basic idea. People have noticed that if they look at windows and very old buildings like medieval churches, they see that the base of the wind is thicker than the top of the window. And this has led some people to conclude, to jump to a conclusion that the reason why the base is thicker than the top is that glass, over the course of centuries has been flowing downward and that it's so slow that it's not detectable under normal situations.
It's only over the course of centuries that you can see the difference. Uh. Here's the problem is that that's just not that's not the case. That's not true, it's not what's happening. Uh. If you look at the glass making approach in the Middle Ages, you'll see why there's a thicker part of the pane of glass. Glass was created generally speaking, in the Middle Ages through something called the crown glass process. It's pretty neat idea pretty neat
way of making glass windows. Here's how it we're in general. First, you get your raw materials h to make glass, and in the Middle Ages that was essentially sand and potash, and you mix it together and you melt them in a very hot furnace. And then you would get a glass blower with a pipe and they would get roll out a lump of molten glass, put on the pipe, blow out the glass. So they expand the glass outward before flattening it, so they don't just you know, create
a globe of glass, they actually flatten it back out. Then, with a flat glass which is still hot and still malleable, it hasn't cool to the point where it is really solidified. You would put that on a disk, a spinning disk, and the disk spins around to draw out the glass to flatten it further, sort of like how a pizza maker will toss and spend dough in the air in order to make that circular pizza. It's kind of similar
to that. So the disk spins and the centripetal force, if you like, is pushing the glass outward toward the edges. So then once that's done, you would cut the glass
into panes so that you could fit them in a window. Now, that would mean that when you would get anywhere close to where the edge of the glass was, the outer edge, because you put the glass on that disk and you spun it around, the outer edge was thicker than the rest of the glass, just because that's where the excess was accumulating as it was being uh pushed outward due
to the spinning motion. So typically window makers would cut pains so that a thicker edge would only be on one side, and they put that side at the bottom at the base of the window, so glass didn't flow to the base. Over hundreds of years, it started out like like that. It was like that from the beginning. That being said, glass is a really interesting substance. It's what we would call an amorphous solid, so saying that
it's a fluid or a liquid is not accurate. But it is an amorphous solid, which is a little hinky compared to other materials that you might be familiar with. So typically not everything, obviously metals and glass being exceptions, but a lot of solids have an ordered crystalline structure, so that means the molecules are organized in a pretty regular lattice. They form a nice repeating pattern that goes
throughout the entire material. When you heat up this solid, those molecules start to shimmy and shake, some of the molecular bonds might start to break down a little bit, the bonds between one molecule and another, the essentially the crystalline order breaks down, and if you heat a solid beyond its melting point, the crystalline structure completely breaks down and molecules will begin to flow freely or as freely as the viscosity of that fluid allows, and there's a
very clear delineation between the solid and liquid stages. You can see the difference molecularly from the way this substance looks when it's in solid form versus in liquid form, and we call that delineation that border between the two the first order phase transition. It's obvious when you look at it from a microscopic standpoint. I mean it's obvious from a macroscopic standpoint too, because a solid behaves one way, in a liquid behaves another way. Now, when you cool
a liquid down, its viscosity tends to increase. If you introduce a nucleation site into the liquid, crystals can form and you get that nice solid structure again once you get down below what the melting point was. Uh, but glass doesn't do this. Glass doesn't form a crystalline structure. Glasses viscosity increases, so it does what other fluids do at that point. But since it doesn't crystallize, it solidifies
in a different way. The molecules actually form an irregular arrangement, not that nice ordered structure that you see in other solids, but that a regular arrangement is still cohesive enough to maintain rigidity. So glass does become a solid, it's just not a crystalline solid. It's an amorphous solid. Now, there's no first order phase transition here. It's not like if you looked at the liquid form of glass and the solid form of glass, you would see a massive difference
in the molecular structure. But there is a second order transition. Now. That transition is a little more subtle than first order transitions and evolves the thermal expansion and heat capacity of a material, So it wouldn't be as obvious to casual observation on a microscopic level, but there would still be differences with the thermodynamics of the material. Ill, so we still would say the glass is a solid not a liquid.
All right, I'm done with glass now, I promise. I had to go on that little track just because it was related to the stuff I was talking about, and I get really irritated seeing that one myth passed around
as fact. So now you know, if you ever go through a a tour and the tour guide says and the reason that the windows are thicker at the bottom is because glass flows over the course of hundreds of years, you can raise your hand and say, well, actually, and tell him Josh Clark sent you, because I don't want that kind of burden on me. I like being able to take tours anyway. Let's get back to Viscosty in general. So, like I said earlier, viscosty is due to internal friction
of a liquid. And you might think that that sounds weird, like how can a liquid have friction inside of it? But we're talking about liquids specifically that have like molecules, and those molecules can have a tendency to resist getting by each other. So some molecules are more resistant you slipping by each other than others. Or a liquid could actually have particles that are suspended in it. It could be a suspension, which is different than just a pure liquid.
But if it's a suspension, it's got particles suspended within the liquid at at some level of density, right, Like some maybe a pretty weak suspension where you don't have a whole lot, but others could have all a greater
density of particles inside a suspension of fluid. Make chocolate bars, let's say, and you're laying out melted chocolate into the mold for the chocolate bars, uh, and it clogs up and you have to stop production and clean out the clog and get everything back up to temperature and start it all over again. It's time consuming and expensive when
that happens. So one solution to preventing it from happening is dilute the cacao more so that those particles don't clump up as much because there there's a less dense cacao component in the fluid. That essentially means replacing cacao with something else, typically something that is less viscous, like that oil that fat. Essentially, so you usually add more fat to the recipe, so you get the more fat
but less cacao. However, it ends up flowing better and creates the chocolate bars that you want without creating the clogs. But it's not necessarily the best product you could create. It's just the most convenient based upon the method of production. So that's where this alternative solution comes in. If you could change the shape of those cacao particles in the fluid so that they packed together more effectively, you would
reduce that viscosity, that internal friction of the fluid. So imagine you've got one of those inflated rubber balls, like like a kickball or something. Now imagine that you're able to grab hold on either side of this ball and pull it outward so that you're elongating it. Now it would become a more of an oval shape, or as
the researchers at Temple University called them, prolate spheroids. Now, the interesting thing about these prolate spheroids is if you align them in the direction of the flow of chocolate, you can pack more of them together. They have these elongated sides and they will fit together much more snuggly. You can create chains of them and chocolate would flow much more readily. But how do you change the shape
of those cocu particles. What is it that you could do to make them actually assume a different shape than their natural globular ball like shape. This is where electric fields come in. Uh, we're gonna talk about applying magnetic or electric fields to a fluid to changes viscos. But first, this doesn't work with every fluid. Uh. Not every fluid reacts to electric fields and magnetic fields in a way
that will alter its viscosity. But it does work in fluids that have certain non conducting or weakly conducting particles suspended in an electrically insulating fluid. Now, we call this a special type of liquid, electro reeological fluid. Electroheological fluids essentially means that when you apply an electric or magnetic field to such a fluid, it changes its viscosity. Sometimes we also call them smart fluids, but more about that
in a bit now. Interestingly, the property was completely discovered by chance. There was an inventor named Willis Winslow who observed the effect in the nineteen forties, and he actually
patented it in nineteen forty seven. Now, for this reason, we sometimes call this effect of changing an electroheological fluids viscosity the winds Low effect, And I'll mostly be using that term from here here on out, because there's only so many times I'm gonna be able to say electroheological before my mouth just decides to rebel against the rest of me and march out the door. And as entertaining
as that would be, kind of needed. Alright, So, applying an electric or magnetic field to such a fluid changes that fluids viscosity within meloseconds like it's practically instantaneous. And if you remove the field, the particles in the fluid will snap back to their original shape, to the fluid's viscosity will return to what it normally would be. So
the change isn't permanent. It only persists as long as the respective field persists, which is super cool because you can do these temporary changes that are really useful in specific situations and then have it go back to normal and it's like it never happened in the first place. But one thing to keep in mind is the direction of the electric or magnetic field is critically important when
you want to make a particular effect. So, in the case of chocolate, if you apply the electric field perpendicular to the direction of flow, you will actually increase the viscosity of the chocolate. You will make it thicker, more like a gel. Melted chocolate will turn into this kind of thick gel. It'll otherwise have all the same properties
that had before, but that viscosity will increase dramatically. However, if you were to apply that electric field in the direction of the flow of chocolate, then you would decrease the viscosity of chocolate and it will flow more freely at that point. Now this makes some sense because imagine that you have these elongated ovals, these uh prolate spheroids. Right, If you stand them vertically, then you can imagine them
slipping through a pipe very easily. If you laid them out horizontally, you could imagine um ending up like like blocking a pipe easily, because it's like trying to fit a long stick through a narrow doorway. If you don't turn it the right way, you're just gonna hit against the door. This is making me think of my dog Tiboalt, who has done this on numerous occasions. He just he can't get it through his little doggy mind. They needs to turn the stick vertical in order to move it
through a doorway. He just wants to charge ahead full steam with the stick horizontal. In many other ways, He's an intelligent dog, so we forgive him this lapse of judgment. Anyway, the chocolate on a molecular level is essentially the same thing. If you are applying this electric field perpendicular to the flow of chocolate, then you get this much thicker uh mixture. And an interesting side note, the electro reeological properties of
chocolate aren't a new discovery, right. I mean, I covered this story for how stuff works now because there was a new application of this property with chocolate. But we actually knew that chocolate would react this way already, at least to the point of increasing the viscosity, because back in there was a Michigan State University grad student who observed the Winslow effect on chocolate, and his name is Dr Christopher R. Daubert, and as professor Dr James Steph
worked with him. They both conducted experiments on liquid chocolate and observed the Winslow effect. Now, in that experiment, Daubert was again increasing the viscosity, not decreasing it, so he was turning chocolate into that thicker gel. That the liquid chocolate into thick gel. Uh. It wasn't until recently that we saw someone try and do the opposite. So that brings us to the Temple University experiment. So you had
these researchers. They had worked on crude oil and decrease the viscosity of crude oil, which is a huge thing for the oil industry to be able to uh move oil more effectively without the fear of clogs or viscosity screwing up things that had been planned ahead of time. They wanted to see if they could in fact use a similar approach to have liquid chocolate move more smoothly through a system so that manufacturers could save money by not having to worry about cleaning up clogs and shutting
down production for maintenance. So They had to test this hypothesis that an electric field directed in the flow of liquid chocolate would reduce viscosity. So they built a cool chocolate zapping gadget. That's not really a zapper, that's kind of a it's kind of not entirely accurate, but I like the idea of using electricity does zap chocolate and make it better. That's just a over simplification of what happened, But that's okay. I'll I'll explain to you what was
actually going on. They built this thing where it starts with a bit of a melting chamber. You can just think of it as like a a pot. It could even be a glass vial. Really, it could just be any little container that can hold chocolate. They put the chocolate in the container and they cover the container, sealing it shut. Uh. They added compressed nitrogen gas into the chamber simply really to to just increase the pressure inside the chamber itself. The chamber was heated so that you
had chocolate melting into a liquid. There was a thermocouple in there to make sure that the temperature was correct so that the chocolate would not overheat or cool down so much that it becomes solid again. And then the base of this container was essentially a drain, so there's like a hole at the bottom of the container that
liquid chocolate could flow through. Attached to that was a tube, and inside the tube they put a series of metal mesh screens, and the screens were what generated the electric field. They had electricity running to those screens and creating electric field that way in the direction of the flow of chocolate, so the chocolate would end up flowing very smoothly through the tube and didn't have any issues. At the other end, they had another vessel container that the liquid chocolate would
flow into, it would cool down solidify. So once that liquid chocolate flowed through into the collecting vessel, uh and once it was free of the electric field, the cacao particles they went back to their original shape immediately. Again. They didn't have to transform or anything. It wasn't a
gradual process. They whoop moved back into those globe shapes that they typically are in, and the chocolate cooled and solidified and was, to all intents and purposes, indistinguishable from the chocolate that was being fed through at the top, you know, at that top chamber. So they were able to reduce the viscosity of the flowing chocolate uh and to the to the point where it was no there
were no issues of clogging. It's perfectly fine. So they were able to prove that their hypothesis was correct, that in fact, this electric field applied in this way would decrease chocolates viscosity. Hooray. But there's more to it than that, So this experiment was not just a success. The researchers actually realized that it had a lot more implications than
just having chocolate flow freely through a machine. Uh. That Again, the reason why chocolate has such a relatively high fat content is to create that oily fluid to reduce viscosity, to have the cacao particles suspended within it at a density that's low enough so you're not likely to clog up the machines. But if you use this approach, if you use the electric fields to reduce the viscosity, you don't need as much oil or fat in your chocolate content.
You could actually start with a recipe that has less fat in it, and the electric fields would take care of the viscosity problem, so you don't have to have as much fat there. That also means you can have more cacao in your mixture. It could be a higher proportion of the overall recipe. So they found that they could reduce the fat content in certain types of chocolate by as much as twenty percent and still have no negative impact on the fluids viscosity. Now, it depends on
what type of chocolate they were using. They were they were actually using name brand chocolates, you know, like like chocolate bars. They would try different types and depending on the type, they could actually end up removing up to the fat in the mixture and still have the chocolate
flow without any problems. And beyond that, the researchers said that people who were tasting the chocolate afterward, because keep in mind, other than the fact that there was less fat in it, there was really no difference between the original chocolate and the end result, they said that the end result chocolate actually tasted better to them. He said, I had a more intense cacao flavor. It was more
chocolate d e than the original chocolate. Now that could be just subjective, or it could be purely psychological, but it's not outside the realm of possibility that by increasing the the proportion of chocolate of cacao in your mixture because you've removed some of the fat, so you've got more cacao per unit of chocolate than you would previously, that you would also affect the taste. It is entirely possible that that is true. It hasn't really been tested
on a scientific level. It's mostly people saying this tastes really good. Also, I should mention this is not the same as fat free chocolate. Fat free chocolate is essentially using some different type of fluid other than oil to suspend cocow particles. So fat free chocolate is has that particular weird taste. It's not It's not the same as the stuff that Typal University was producing. So, uh, I
just want to clear that up. It's not like you would take take a bite of a brand new chocolate bar that was made using this procedure and they, oh, this tastes like fat free chocolate. No, So the end result here is that we could end up with better tasting chocolate with less fat in it in the future,
which seems pretty awesome to me. Now, Earlier I mentioned that electro rheological fluids are also called smart fluids, that's cause these fluids can change their viscosti almost instantly in the presence of an electric or magnetic field and then go right back to what they were before once the field is turned off, and they become really important in ways beyond making superior chocolate. For example, car manufacturers have
been using smart fluids and suspension and breaking systems. Uh. The fluid can actually go from relatively thin too thick and just a moment's notice, which makes it superior to a lot of mechanical solutions that would take time to propagate through a system. And you can have a variable suspension in this way. Imagine that you have a suspension, it's a fluid suspension, like literally it's a suspension for a car with fluid in it, not that it was a fluid that has a suspension in it. It's kind
of confusing. So car suspension's got fluid in it. Very high end sports cars have these, and you can set your suspension to different modes, like you can predetermine which mode you want at any given time. So let's say you're gonna be driving on like a racetrack, a nice smooth racetrack, and you're really gonna push the car to its limits. You might want a pretty stiff suspension for that to really be able to feel the car as you're driving along this very smooth surface. But that stiff
suspension would be torture device. If you were driving down a normal everyday road that had some bumps and maybe some potholes in it, that would be very jarring. You would feel every single little bump. So in that case you'd want a more you know, loose suspension, a little
spring in it. So you might want to reduce the viscosity of the fluid inside the suspension to allow for more um give really, and you could do that with a smart fluid and just change the electric or magnetic field that ends up affecting the viscosity of the fluid. So you can actually have settings and say I want a very stiff suspension in this circumstance, and so it generates electric field, the viscosty increases and you get your
stiff suspension. Or he might say, oh, I want it to be a more forgiving suspension, and it turns off that electric field, the viscosity decreases and you have your more your your suspension when more given it, it's a pretty cool idea. At chatted with Scott Benjamin about this before I came in here. He was very interested when I started talking about chocolate, but then when I started talking about smart fluids, he really lit up because he
knew exactly what I was talking about. I mean, Scott is a car genius and knows everything there is to know about cars, it seems. So we had a good discussion about, you know, the physical properties of smart fluids and why they behave the way they do. So this technology could be used in lots of different applications moving forward. When you can induce some mechanical change in a fluid with something as simple as an electric or magnetic field, a lot of different opportunities open up. But for me,
you know, I'm happy with the chocolate thing. I'm going to settle for that because I do love me some chocolate. Al Right, guys, Well, this kind of wraps up this episode where I really wanted to look at the physics and technology behind ostensibly making chocolate manufacturing more uh smooth and efficient, but ultimately could result in better, more delicious,
less fattening chocolate. That doesn't necessarily mean we should all go out and eat more chocolate by the way, not that that ever stops me, but I feel like as an adult, I have to at least say, don't go out and just eat more chocolate. Even if we ultimately have chocolate with less fat in it, that's not that's not a good excuse. Uh, do as I say, not as I do. Anyway, I wanted to invite you guys to get in touch with me. Let me know what sort of topics you would like me to cover in
the future. I've got some interesting future topics lined up. He would like a quick peek into the future. Pretty soon, I'm going to be doing an episode about the story of Pixar. I'm gonna do a full maybe two parter on that because it's a it's a good long story. I've got a an interview lined up with some folks to talk about Amazon Alexa and developing apps for that
and what Alexa might mean in the future. I've got uh an episode lined up with Mr Scott Benjamin, whom I just mentioned about robo rites, and also the tragic tale of the first Death and an autonomously operated vehicle. So we've got a lot of different stories coming up. But if you guys have a specific text story, or technology in general that you would like me to cover. Get in touch with me, Let me know I'm I
love hearing from you guys. You can email me. The address is text stuff at how stuff works dot com, or you can drop me a line on Facebook or Twitter at both. I am Text Stuffs H. S W. And I'll talk to you again really soon. For more on this and thousands of other topics, is it how stuff works dot com, wh