Oh, be careful, Squeaks! I accidentally knocked over this flower vase, and I'm cleaning up the water.

Aw, thank you! I'm ok. I'm just a little wet! And at least the glass vase didn't break... ...although if it had broken, it wouldn't have gone into the trash.

We could have recycled it so that it became part of some new bottle or jar!

Recycling is when you take something that's trash and turn it into something new.

When glass gets recycled, it's usually crunched into chunks, and then those get heated up until they melt.

The melted glass can then be molded or shaped into new bottles and jars… and those can get made into new bottles and jars!

It's one thing to love about glass… it's recyclable over and over and over again!

Oh, good question! Squeaks wants to know where glass comes from in the first place!

It might sound hard to believe, but glass actually starts out as sand!

Yes, the very same stuff that covers the beach and fills our sandboxes!

If you look really closely at sand, you'll notice that its made up of lots of tiny pieces called grains.

To make glass, you have to heat up those grains to a really high temperature — way hotter than we could ever do on a stove. I'm talking "inside of a volcano hot".

When sand gets that hot, it melts…and those little, gritty grains change from a solid into a liquid.

Yes, you're right, Squeaks! It's just like ice and water.

Ice is a solid. When it gets warmer...it melts… and turns into liquid water.

Now Squeaks, what would happen if we took a bunch of ice cubes, melted them into water, and then cooled them down again? Would we get the cubes that we started with?

That's right — we wouldn't. We'd end up with one huge block of ice instead.

And that's essentially what happens with sand, too.

And once you have liquid sand, if you cool it down again, it doesn't turn back into grains. It stays together in one piece — a piece of glass.

If you want to get that sandy texture back, you have to break the glass back down into tiny little pieces!

I think I know a way that we can show how this all works right here at the Fort!

Now we can't melt sand… that would be way too dangerous. But we can use a sweet substitute: sugar!

And you know… it's almost time for Valentine's Day! So we can show how much we love science by making some glass candy hearts!

Now, you can do this with regular sugar, but it's a lot harder; you have to make it really hot, but not too hot… and, well, it's pretty tricky.

So instead, we'll use a sweetener called isomalt. Let's take a good look at it!

The isomalt really does look like sand! It's a solid. And it's grainy.

Isomalt isn't pink like this usually, that's a food coloring that's been added to it.

Before we start making our glass candy hearts, let's take a look at what happens when we heat it up!

Yeah! The sugar grains melted together and turned into a runny liquid!

We have a heart-shaped mold that is safe to put in the microwave, so we'll pour our isomalt in and microwave it.

If you don't have a mold that can go in the microwave, you can also use a microwave-safe bowl or heat it up on the stove.

And then pour it into your molds after it has melted. And now, we wait for it to cool!

What do you think will happen when our sugar cools? Do you think it will turn back into sugar grains?

I don't either, but we'll have to wait and find out!

Okay, our hearts are nice and cool. Let's see what happens when we take them out of the mold.

You were right, Squeaks! Look at that. The melted liquid sugar got hard and clear.

It didn't go back into grains at all. It kept the shape of the mold — a heart!

It's just like if you poured melted sand into a mold to make a glass heart.

You're right! Squeaks! Our candy is different from glass in a very important way… we can eat it!

Thanks for joining us. If you want to keep learning and having fun with Squeaks, me, and all our other friends, be sure to hit the subscribe button, and we'll see you next time here at the fort!