[ INTRO ].

Squeaks and I are celebrating today. Because guess what?

It’s almost National Coloring Day! [Squeaks cheers]. National Coloring Day is just what it sounds like: a day to color and have fun. And that’s exactly what we’re going to do … with a special project.

We’re going to make some invisible ink! That means the ink will disappear, and then you can color over it to reveal a secret message. All you’ll need is baking soda, water, purple grape juice, two cups, a cotton swab like a Q-tip, and either a paint brush or a cotton ball.

Oh, and a piece of white paper to write on, and a grown-up, of course! The first thing we’ll do is mix a quarter of a cup of baking soda and a quarter of a cup of water. The measurements don’t need to be exact — we’re just trying to make sure we have about the same amount of each.

This baking soda-water mixture will be our ink! [Squeaks is surprised by how simple it is]. Yep, that’s all there is to it! Let’s write something on this paper here.

Hmmm … let me think of a secret message for you, Squeaks …. OK! Now all we have to do is wait for it to dry, and the message will be hidden!

It looks like the ink is dry, so the secret message is ready to be revealed! The question is, are you ready, Squeaks? Let’s do it, then!

This is what the grape juice is for. We’ll dip the brush into the grape juice, and paint over the message. Check it out!

Science is awesome. That was the message! There are lots of ways to make invisible ink at home, but this is one of the easiest — and, I think, the coolest!

Because we’re doing the same thing lots of scientists do in their labs every day! No, they’re not writing secret messages. But they do mix things together to learn more about them, like we just did!

The baking soda we used to make the invisible ink is really a type of chemical called a base. And when we added the grape juice to the base on the paper, they reacted to each other! That means they changed.

When it touched the baking soda, a chemical in the grape juice changed to become darker. That’s why the parts of the paper where the message was got darker, and we were able to read it! Now, baking soda is a safe chemical, so we can cook with it and use it for experiments at home, but scientists use it in their labs sometimes, too.

Actually, scientists use all kinds of bases in their labs, and sometimes they need to be able to test if a chemical is a base. To do that, they combine the chemical with something called an indicator. That’s another chemical that scientists know will change color if it mixes with a base.

And guess what? One of the ingredients in grape juice works as an indicator! It’s called an anthocyanin, and it becomes a darker purple color when it touches a base. [Squeaks points out that grape juice is already purple].

That’s true, the grape juice is already purple! But when it touches a base like baking soda, it becomes a much darker purple. So that’s the scientific secret to our invisible ink.

And now we can write all the secret messages to each other we want … as long as we have some grape juice on hand! Thanks for joining us! If you want to keep learning and having fun with Squeaks and me, hit the subscribe button, and don’t forget to check us out on the YouTube Kids app.

We’ll see you next time, here at the Fort! [ OUTRO ].