We Turned Sugar into a Light Source!

Hi. Today we're going to make rock candy. Now, I know this isn't a microwave weapon system or stealth technology, but bear with me because the rock candy is just the start. And this is a great project if you want to involve students or children because who doesn't like to make candy? Now, if you're interested in making rock candy, you can go on YouTube and you can find over a dozen channels that show you how to make rock candy at home. I know because I've watched them. We're going to take a little different approach here. laboratory approach, but nevertheless, when I'm all done, what you'll learn here, you can do with equipment that you've already got at home. And the minimal ingredients you're going to need are water and table sugar. That's it. Now, to begin with, one of the things that I think you might find kind of interesting is that instead of dissolving the crystal sugar into the water on a stove, we're going to be using a laboratory hot plate. And these things are kind of neat. You can spend hundreds and hundreds of dollars on these and you can get a very excellent unit. But if you have occasional need to use one or you're an amateur, you can pick up one of these on am on Amazon or on eBay for maybe $100 to $150. And they're pretty neat because in addition to having a hot plate, underneath the hot plate is a small motor. And attached to the motor is a small iron bar which couples to a magnet that's coated in Teflon that sits inside of the liquid so that when you turn on the motor, it will continually stir the liquid and keep things nicely blended. And I've actually used this in the kitchen because it's great when you're doing reductions. You don't have to be standing over the stove stirring constantly. This can run for minutes or it can run for weeks. Another neat feature is this. It's a temperature probe. And the temperature probe can be placed directly into the liquid itself. And it allows you to monitor the temperature of the liquid that you're heating. And it feeds back through this cable to a controller underneath the hot plate. And so it can maintain the temperature of the liquid at an exact temperature to better than a degree Celsius. It's not like a stove where it's low, medium, or high. So these are very convenient features. Now I'm going to turn this on and begin heating up the liquid. And as I do so, what I'm going to be doing is measuring out the powdered sugar slowly. I'm not going to pour it all in at once because it would kind of defeat the purpose of the stirring bar. We just lock it up. You'll see the numbers here flashing. The high number is the setting, the eventual setting when this thing would try to maintain the temperature. I've got it way above where we're going to need because we're not going to be using the temperature control function. The other number, the lower number, represents the heat of the liquid. And you'll slowly see this number rise as the hot plate begins to get warm. Now, I'm just going to start adding in the sugar a little bit at a time and continually stir this. And it will take probably about 20 minutes or so for us to get to the point where we've dissolved all of the sugar. Well, we're already at 40°, so it's coming along. 52 56° 60° so it won't be too long. 75° 78° 81° 86. All right. Now the next question you're going to ask is what's the ratio of sugar to water? Now I've done a lot of experiments and I've come up with a good ratio. But in a laboratory you will almost never measure a granular or powder type of material using volume simply because depending on how long it's been sitting, how it compacts during storage, you can have a wide

variation in the amount of a powder or a granular material that you add even given the same volume. So, you will always do things by weight. And after experimenting a number of times on this, I found a sweet spot, a good ratio, and it's simple and easy to remember. Three parts of sugar to one part of water by weight. Now, you can vary that ratio a little bit. You can go down to a lower ratio of sugar, say 2 and 1/2 to one. But what happens is the process will take much longer. You'll get nice large crystals in your rock candy, but it could take a week to 10 days to finish the process. If you go up to say 3 1/2:1, you'll end up getting the process done in about a day and a half, but the crystals tend to be very tiny. So 3:1 works out to be a very good ratio, and after about 3 to 4 days, you'll have excellent rock candy. Now, something I want you to note here. You notice that the temperature is reading at 94. 7° and we still haven't dissolved all of the sugar into the liquid. I haven't even added all of it yet. I want you to keep that in mind because I'm going to refer to this fact a little bit later on and explain what's going on. All right. You'll notice the temperature here is at 102. 4 four and the liquid is not yet boiling even though it's above the normal boiling point of water. This is because the sucrose molecules tend to hold on to the water molecules a little bit more tenaciously and increase the boiling point. But we're getting very close. And as the liquid approaches the boiling point, you're going to see a couple of interesting things happen that I'm going to point out. The first is you start to see a little bit of bubbling occurring up here because it's hotter at the bottom than obviously at the top. You'll also notice that there's starting to be a foam layer that's occurring at the top as the bubbling is beginning. The foam is caused because we're outgassing air that's been dissolved into the water. And also because the top is a little bit cooler than the hot plate below and where the temperature probe is. As a result, that foam is caused by the residual particles of sugar that haven't quite yet dissolved. That foam will not last very long. And in a brief period of time, the syrupy thick bubbles will begin to appear. And then you're going to notice something that occurs in a very, very short period, usually just a few seconds. You see how the mixture is still kind of opaque or cloudy and then all of a sudden it will become transparent or translucent. You can see it's starting to happen right now. And the reason for that is simply because we've gotten rid of all the particles and the foam is beginning to thin out as finally we're getting the top layer hot enough. Now, as this continues to boil, you'll see the foam begins to disappear. the larger bubbles begin to rise. And I usually let this phase go for maybe 2 or 3 minutes just to make sure that we've gotten rid of every single crystal of sugar in here. But you don't want to go much longer because we're actually driving water out as it boils. And as a result, we're changing that ratio that I established in the beginning. Three parts of sugar by weight to one part of water by weight. The slight amber color you see is simply because when they process the sugar, there's a few amino acids and a little bit of cellulose from the beets or the cane that the sugar was derived from. This will not end up in the rock candy, but gives a slightly yellowish amber hue to the syrup that's inside of the beaker. Now, what I'm going to do is leave the stirring function on and I'm going to turn off the heater. And we are going to let this begin to slowly cool down. And then I'm going to show you something kind of interesting. All right, we're cooling down slowly. And as you can see, the temperature I've set the setting way down to 10° so the heater wouldn't work, but we'd still read the temperature output. And we're at 89. 5°. But you notice I've added all the sugar. And this is still perfectly clear even though at an even higher temperature with not all of the sugar added it was completely cloudy. What gives? How does that make sense? Well, it's an interesting principle in crystallization. You see, when you try to break apart a crystal, you have to impart energy to do that. [clears throat] It's the same thing that happens when you have, say, a cold drink with ice cubes in it. As long as the ice is still present in the drink, the temperature doesn't change.

Even if you put your warm hand on it, you put it on a warm table, it remains at the same temperature because all of the added heat is that work is being used to break apart the ice crystals and form liquid water. The same sort of thing is happening here in the dissolution process. As we're trying to dissolve the crystals and break them up, we have to add heat [snorts] to do that. At a given temperature, we need even more energy in order to do that. So that's why it doesn't uh dissolve even at a higher temperature than we're showing right now. The reverse is true. When you take water and you put it into a freezer in the ice trays and bring the temperature all the way down to 0 degrees C, it doesn't freeze. You need to stay there for a while to pull out additional energy to allow the crystals to begin to form. And that's exactly what's happening here. We need to remove energy, but it's still too hot to do that. Nevertheless, we have a super saturated solution. This is not stable and if we gave it enough time eventually this would block lock up into a solid cube of sugar. But the process is extremely slow. It can literally take weeks and it is that long duration that gives us the opportunity to make the rock candy before this all locks up into a crystal. So, what we're going to do is I'm going to turn off the stirer and I'm going to remove the thermal probe put on a couple of gloves here [snorts] and we're going to transfer this liquid into the container we're going to use to grow the crystals. Now to do that we have to be very careful because this is one of my first warnings. This process making this is extremely dangerous. The reason it's dangerous is because you go into a microwave, you're in a hurry, you boil a cup of coffee, you pull the coffee cup out, you get a couple of drops of water on your hand, you're like, "Ah. " But you're probably going to be okay. You get this syrup on your hands, just a single drop, and you're guaranteed to get a blister. Not only is it at some points hotter than boiling water, but it's [snorts] sticky. It adheres. So, if you've got students or children around while you're doing this, make sure your body is in between them and the hot liquid. In addition, follow good laboratory and kitchen techniques. Make sure that you don't have any unnecessary debris around that you could bump into. And this is a process that you don't want to do while you're enjoying an adult beverage. Keep your wits about you. Now, I'm going to clean this up here, and I'm going to get the container that we're going to be using to fill. Now, the top of this is cool enough that I can lift this off carefully. And then what I'm going to do is I'm going to take this tefloncoated magnet and I'm going to attract it to the side of the container with this little additional magnet. This will hold this in here so that when I pour the liquid into the other container, it doesn't plop down and send a bunch of hot liquid all over the table. Now, I'm going to pour this slowly. And as I do so, another safety measure you have to keep in mind is that all of the hot containing liquid glass that's containing the hot liquid must be made out of borosyicate glass, sometimes called Pyrex or ChemX. There's a bunch of different brands. The difference between that and typical soda lime glass like your glassware is made out of is that it has about onethird the coefficient of expansion of soda lime glass. And as I pour the liquid inside of here, the inside of the container almost instantly heats up to the temperature of the liquid, but the outside lags. And so the inside of the container tends to expand and the outside won't let it. It can crack. So be careful. All right. Now, what we want to do is we want to form the rock candy and we want it to form around something so that we can remove it. Now, you'll see some YouTube videos where they suggest using something like string. You take twine, you wet it, and then you dust it with some sugar particles. I would stay away from the twine simply because it tends to float. It's difficult to control. And

so what I'm using here are these wooden dowel rods that have been placed inside of holes that I have bored to fit them. These are 6 mm or 1/4in dowel rods. And the boards are there in order to support them so that we can rest this in the container and keep it away from all of the sides so that the uh rock candy doesn't end up sticking inside. Now I'm going to adjust the length of this because it's a slip fit so that I'm about a centimeter from the bottom of the container. And then I need to coat this with some sugar in order to create uh a seed that allow the crystallization. The way that works is because compared to say a sucrose molecule, the sugar granules as tiny as they are enormous. And so when a sucrose molecule drifts by one of these crystals, it can dump some of its thermal energy into the crystal and stick. It's much more likely to occur than two random sucrossse molecules finding each other and getting together in the solution. This speeds up the crystallization where we want it to occur. Now, in order to dust this to get a nice coating of sugar crystals to act as seeds, I'm going to show you a little trick here. The sugar crystals that I'm going to be using, just the table sugar. If I dip this in some water and try to dust this with some sugar crystals, it won't stick. There's not enough time for the crystal to make the water sticky and stick onto here. So, you'll spend 5 minutes trying to get a coating. And if you just dip this in the syrup and try to put the crystals on, again, it's not going to stick. So, the trick is this. Place the dowel rod into the syrup for a couple of seconds to coat it. Then pull it out and dip it for about two to three seconds into room temperature water. This makes the outer surface stickier. And so now when I dust this with the sugar, it sticks very readily to the outside surface and produces a nice even dense layer of seed crystals all over the rod. This took a little bit of experimenting to figure out how to make this work right, but the result is very nice. A nice even coating that doesn't take very long to do. And you can, if you want, make a batch of this and just make 20 or 30 of these things so you don't have to dust them each time you decide to make a different color. And now you have a nice coating of crystals. And what we're going to do is we're going to let these crystals dry for a couple of hours or maybe half an hour or so they really adhere well. And then what we're going to do is allow the syrup to continue to cool. It's still a little hot. If I was to put the crystals in there right now, a lot of them might dissolve into the liquid. And we're going to remove the seeds. And if I wait all the way until this is at room temperature, it becomes so thick, it can actually pull some of those crystals off, distribute them around the bottom, and increase the parasitic crystallization that we're going to get inside of here. And we don't want that to happen. So, what we want this to do is to cool down to roughly about 50° C. It's not a very precise number. You can use a thermal probe like this. I put this right on here. And I don't know if you can see this on the camera over there, but it says 69° C. If you don't have one of these, you could use the thermal probe. Or literally, you could wait until you can pick this up and hold it up for maybe a second or so. It's a little too hot to touch, but you can put your fingers on it for a second or so. That's about the level of precision you need. And then you can put the stick in there and you can begin to do the growing process. Now, if you want to add color or flavor, the time to do that is in the beginning of the process when we're first starting to heat up the water. That's when these compounds will get well mixed and you won't be cooling off a gel or having trouble with clumping. And so, with the colors, I did a lot of experimentation. And originally I wanted to stay away from the liquid dyes primarily because they're not very colors saturated. You need to use a fair amount of them in order to get nice rich colors. So I had tried a number of samples of dry powdered dyes. These are extremely

saturated. You don't need to use more than a gram or two and you get a very rich color like you can see in these beers over here. Very dense color colorization. The problem is and it's unpredictable is some of these powdered dyes have other particles in them. Something the manufacturer leaves in them which isn't a problem if you're making icing for cupcakes. But the problem is during that foaming phase when we're originally heating up the liquid, it can create a tremendous amount of foam. The orange in this manufacturer's American color was one of the worst I ever worked with. It nearly tripled the volume in the container. And unless you had an enormous pot, you've got a huge mess that you're going to have to clean up. So after that experiment and deciding that the powdered dyes are a little unpredictable, I went back to the liquid dyes. And the McCormick and the Watkins, they work very good, very well. And you have to use a fair amount though. For the recipe that I'm using here, which is 200 cc's of water and 600 g of sugar, you need to use 10 g or 10 ml or 2 teaspoon of the dye in order to get a nice rich color, which is a fair amount when you're cooking. You never use that much, but you need it for this purpose. Now, don't worry also about the additional volume. It's not going to matter. Now, if you're going to add flavor, it's also good to add it at the beginning, just like the color. You can add things like citrus oils, lemon oil, orange oil, anis, uh, licorice, maple, vanilla. And they blend in well, and you do it to taste. It's a few drops. You don't need to use very much. One interesting thing you might notice is if you take a look at these two rock candies that I made over here, they are not colored. They were flavored. The pink one is actually flavored with our ghost pepper extract that we made about a year ago and it's an interesting taste. Uh it's sweet but it's extremely hot. So it's kind of a fun experiment. But my real favorite was this one over here that is flavored with woostachir sauce. Seriously, you take 30 cc's or essentially you take about oh 15% of the volume of your water and replace it with woostachir and then everything else is exactly the same. The taste is sort of like a barbecued potato chip. It's kind of salty, a little umami and sweet. And you take one of these and put it in a bloody mary and you're going to be really popular. Now, one of the things that you might also notice is that when we're done, we're going to be using this entire volume of liquid in order to make one rock candy. And that might seem a little bit wasteful. And so one of the things that I decided was it might be a good idea to try to use a smaller, thinner container like this. Because of its smaller diameter and its greater height, I don't even need to use the same volume I used in here and I could make a much longer rock candy. Not a good idea. The problem is because of the parasitic crystallization, eventually after a few days, the crystals form in the wall on the bottom as well as on the stick. And eventually they get so well attached that you can't get the rock candy out. I would have to break the stick in order to try to free this up. So, that's not going to work very well. I came up with a little bit better technique. I thought. But before I show you that, I'm going to show you what it looks like when we're done with a 4-day growth. Now, this is cherry flavored and red dye colored. And I'm going to show you what it looks like when it comes out. Now, sometimes you have to break this up a little bit from the bottom if it sticks. And you might have a little bit of crusting around the top that you can break up here a little bit to make sure it's easy to get the rock candy out. When you do so, it's beautiful, but it's dripping. This took almost 3 days, and it would continue to grow for another couple of days if you wanted to get it larger. But because it's going to drip for a while, what I do is I will place this over a little drip basin and put a

weight here to hold it. And then you can simply let this drain overnight. And when you're done, you'll have those products over there. Now, one of the problems, like I described, was this crystallization and the waste of the liquid. And I thought, wouldn't it be kind of cool if we could induce the crystallization to happen more quickly on the stick to stay way ahead of the parasitic crystallization that occurs inside of the container. And I came up with this. This is a refrigerated rock candy stick. And what it consists of is an anodized aluminum rod. So it's food safe. It's the same as cookware. and it is bolted to a thermally conductive aluminum plate. This acts as the support so that we can place this in the container and hopefully grow the crystals much more quickly and allow us to grow larger ones and not have to wait so long. On each side is a solid state refrigerator. It's based on a device called a peltier device. These are very interesting. They're sometimes called TEC's or thermo electric coolers. You can get these for a couple of bucks on Amazon or eBay. They're very inexpensive and they consist of a couple of very thin ceramic plates that give it structure and then in between there is a whole array of hundreds of bismouth telleluride semiconductors. Because of the PN junction, when you run current through here, what they will do is they will pump energy from one side to the other. One side will get hot, the other side will get cold. And if you reverse the direction of the current, one side will get hot and the other side will get cold. These things are very popular in computer and electronics uh community in the laser community because if you hook this up to a temperature controller you can maintain or cool off a component and maintain a temperature to a very small fraction of a degree Celsius. It's very convenient. In addition, you can stack a number of these things on top of each other and achieve temperature differentials of over 150° C. It's not quite enough to liquefy air, but it is remarkable in how it works because there's no vibration. There's no fluids. It'll never leak. And like I said, they're very expensive. But you can go another step. You can actually invert the whole process. If you make one side hot and allow the other side to get cold, you can actually create current. And that's exactly what we did a couple of years ago when we built this, the campfire generator. It has a whole array of these Peltier devices wired together and using the heat of a campfire and the cold water from a nearby stream, we were able to generate enough current to illuminate the campsite. It was a lot of fun. So, if you're interested in these devices, I give you more information about it, and it's kind of fun. You might enjoy the video. Now, despite all of that technology, it turns out that I really wasn't too happy with the consequences of using this. What happened was it works very fast. I was able to make this rock candy form in one of these syrup containers in about an hour. But as it turns out, time matters. Just like I brought up with the concentrations that can be used for different periods of growth and different size crystals. This grows too fast and as a result, you get very small crystals. They almost look like you just took the sugar crystals you dissolved initially and just put them back on here. So the point is not everything I do works. Now this is around 50° C. I can measure this well 54. Close enough. So, what you're going to do is we'll take this lid off that I was just using to help prevent a little crusting on the top as it super cools. Take the stick that we have allowed to cool. I'll take one of them that I made before. And I'm going to insert this in here like this, right in the center. And then grab a little bit of plastic wrap and cover the assembly here. just pop it over the stick like that and wrap it around here. And

this isn't really to prevent evaporation, but it keeps out the dust. bugs and it locks this into position. So, if we move this around a little bit, this isn't going to be sliding over to the sides. So, pretty thorough. I think if you were to follow these instructions, you're going to end up with very, very nice rock candy. And you can pick flavors colors to your heart's content. Now, some of you may be saying, "Okay, all right, that's cool, but it ain't rocket science. " That's true. So, let's dial this up to 11. All right, let's get a little more serious here. Now, you remember what I said about the process of crystallization and breaking of crystals? Well, what holds the sucrose molecules together is called a covealent bond. Effectively, when they get close to each other, the outermost electrons in each sucrose molecule can begin to be shared between the individual molecules. This is the same bond that holds carbon atoms in a diamond. So it can be a very strong bond or a weak bond in the case of sucrose. Nevertheless, because the electrons are shared, if you suddenly fracture the crystal and tear apart the structure of the crystal, there's a chance that some of those molecular bonds are going to be broken. and one of those electrons is going to be trapped with one of the sucrose molecules and end up becoming negatively charged. The sucrose molecule that lost its electron is going to be positively charged. This isn't stable. And so what happens is that electron slams back home and in the process creates an electrical spark, an actual electrical current. This process then will stimulate or drive nitrogen atoms in the air to produce light, UV light in the 300 to 400 nanometer range. This process is called triboluminescence and it's well known in science. Now the point is you don't see this when you crunch down on a piece of sugar or something like that. You don't see this light. First of all, it's quite dim. But secondly, because it's in the 3 to 400 nanometer range, your eyes simply can't detect it. You can't see that. But there's a way to cheat. If you introduce a fluorescent molecule, something that can be stimulated or absorb that UV light and downconvert it to a longer wavelength in the visible range. You can then see the flash of light that occurs when that current is developed. Well, you might have heard of sort of a saying that if you took a lifesaver, a wintergreen lifesaver, and you crunch down in the dark, you can actually see a blue flash. This isn't an urban myth. It actually does occur. And one of the experiments we're going to show you is I'm going to take some of these winter green lifesavers and I'm going to smash them in a very dark environment and we're going to see if we can see that flash. So, let me get in here and then I'm going to ask Alex to turn off the lights because it is quite dim. All right, hang on just a sec. One sec. All right, Alex, you can turn off the light whenever you're ready. — All right, three, two, one, off. All right, let me get my eyes a little adjusted here. In three, two, One. Wow, I made a mess. But as you can see, it actually does

work. I needed to use a lot of these simply because it is quite dim and the flashes are in the nancond range. So, there's a chance the camera is only going to pick up a few of them. Well, the fact is we can actually do the same thing with the rock candy. If we introduce a fluorescent dye and the dye that is being used in the wintergreen lifesavers is wintergreen or methyl salicellate oil of wintergreen. And this is methyl salicellate. And if we place a little bit of this into the bath, just like we put the flavor or the color, it will grow into the crystals and we can smash that and we can actually see the light. Now, I've given you some warnings and this is a warning I want to give you about this particular compound. It is not poisonous but it is quite powerful because methyl salicellate is closely related to acetto salicylic acid or basically ASA or aspirin. It's the salicellate that is the active compound. And a single teaspoon of this material 5 milliliters has about the same potency as 20 adult aspirin. So, it's not poisonous, but it is quite powerful. And so, if you are going to do something like this and you're going to put the oil of wintergreen into your mix, be aware that if you have an aspirin allergy or you are in blood thinners like warin or couadin or you're nursing or you have an infant, you probably want to stay away from this. But in terms of the actual dose, this is very water insoluble. And so it would be impossible to put more than about half a gram, 500 mg, a little more than an adult aspirin, and an entire liter of the growth syrup. And only about 10% of that ends up inside of the crystal. So it actually is a very low dose. And it turns out it's actually a little bit less than in one of these lifesavers. So, not a big deal. Now, the point is I'm going to show you when I crush some of the crystals that I've obtained from the growth in the same chamber. And I've scraped them off of one of the sticks. So, I have it in another mortar and pestle. I'm going to go in there and I'm going to smash them. and we're going to see if we can see the light. As I said, I made a bit of a mess in here. All right, let me get position. Okay, Alex, you can turn off the light. All right, in three, two, one. — Okay, I'm going to begin smashing in three, two, one. Man, it smells like winter green in there. It's pretty powerful. I kind of like the flavor, but the point is not everybody does. And so if it turns out that you can't tolerate oil of wintergreen or you simply don't like the taste, there is another dye that you can use that will produce a little different color of light. This is the scrapings from one of the candies that I made using a compound called sodium florosine. Now, this is kind of an interesting and very non-toxic material. You can buy this on Amazon for about six bucks. This is 10 g of it. And it's typically used in plumbing applications where they will place a little bit of this dye in a pipe and then with a UV light, they can see the glow of the fluoresence and be able to detect even less than a drop of water. It really makes it convenient. And as a matter of fact, it's used in the medical community to do an examination. They will literally inject about half a gram of this material intravenously in order to make your blood slightly fluorescent. And then an opthalmologist will perform opthalmologic angography.

They will actually look with a microscope into the back of your eye through the globe and visualize the retina and they can see the blood vessel patterns, they can see leakage into the vitrius. They can also see blockages in the blood vessels. So, it is quite non-toxic. And what's also nice is if you don't like the flavor of wintergreen, this is flavorless and it glows very brightly in UV light. I have one of the rock candies that we made. And I have a little UV light here. And you can see the color that's going to occur when I smash this. — Should I turn off the light? — Well, you don't need to for this. I think everybody can see this. But why don't you try it and let's see what happens. Okay. Off. — Okay. You can see it's amazingly bright and it doesn't taste like oil of wintergreen. Okay, why don't you turn on the light and we're gonna smash this. All right, you need to check the camera again or you good. Should be fine. — All right, let's go ahead get another mortar and pestle here. Get this going. All right, let's get this out of here so I don't bump it. — Yeah, just keep everything in the same position. — Yeah. All right, here we go. I'll tell you when to turn it off. — All right, [snorts] I'm ready. You can turn it off now. — Okay. Three, two, one, off. — All right. Three, two, one. Now, it's not quite as bright as the methyl salicellate, but as I said, it's safer and you can get this on Amazon. This is a little bit more difficult to obtain. You have to go to a chemical company. But I thought this was kind of neat. It's sort of an interesting way to demonstrate some pretty interesting principles. And what's kind of cool about this whole thing is that we started with rock candy and we finished here with triboluminescence and quantum generation of light. And that's why I think this is a great project to involve students or kids because everybody likes candy. And in the process, they get exposed to some pretty important principles in physical chemistry, electronics, and even a little bit of quantum mechanics. Sneaky, huh? Well, I hope you like this. Uh, this was a lot of fun to do. And if you follow the safety rules that I've given you here, this is quite safe. You just have to be aware of them. And if you like the kind of things that we're doing on this channel, please, it doesn't take more than a few seconds and doesn't cost you a penny. Please subscribe. And if you give us a thumbs up and a comment, all three things will tend to push the YouTube algorithm to distribute our videos to a much broader audience, and that allows us to do more videos and more frequent videos. And if you really like what we're doing, take a look at our link to our Patreon page because it's a direct contribution to the channel and it allows us to avoid the sponsorships which can interfere with the flow of these videos. So, we'd really appreciate that. And finally, after each one of our videos, the day after release, so if this is released on a Saturday, on Sunday at 6 PM Eastern time, we will do a live stream where we can discuss all of this. We can cover any questions or comments you want to make, as well as any of the other videos that we've done or just science, engineering, and technology topics that you find interesting. So, please stay safe, have fun, and we'll see you tomorrow night.