Why Is Tape Sticky?
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I'm Jane Lindholm. Every episode, we take questions from you, our listeners, and it's my job and my co-producer Melody Beaudet's job to find cool people to offer an answer to whatever's got you wondering. Our podcast is celebrating our second birthday this month. We've put out more than 60 episodes since we got started. Have you heard all of them?

We have a lot of new listeners, so we thought we'd remind you of one of our favorite early episodes. It's all about how you can make your own paint using rocks and spit. We're also going to answer a couple of new questions. Why is tape sticky? How do erasers erase? We'll get to the new questions later, but first, let's learn how to make paint. My name is...

Addison B. I am five years old, and I live in Edmonds, Washington, and I want to know about how we make paint. There are a lot of different ways that paint is made. If you're painting your house, you're probably using industrial paint that was made in a very big factory. There are lots of chemicals involved in making the kinds of paints we use for things like houses or cars or things that need to be resistant to rain and dirt and kids drawing on the walls.

There are also paints used in art projects. Some of these paints are also made in big factories. But you can make your own paint with just a few household supplies. A lot of the recipes you find might include food coloring as one of the ingredients you need. Well, that's kind of cheating if you really want to make your own paint, because that's already a blended-up pigment, the thing that makes paint whatever color it is.

So we thought we'd ask a guy who makes his own paint from scratch for a lesson in how you can make your own paint from start to finish. My name is Nick Netto. Nick is an artist in Vermont. At his home studio, he has all kinds of supplies for making art, and he makes most of them. So his paintbrushes might be wood from a local tree for the handle and the hair of a deer for the brush. His process for making paint is pretty cool.

Let's hear Addison's question one more time before we hear from Nick. I want to know about how we make paint. Cool question. People have been making paint for thousands of years from various sources of pigment. Pigment is the thing that makes paint colorful. It's the little particulate that gives paint its color. And basically you can break it down into getting your pigments from rocks or from plants and, you know, funguses even.

So I'm really interested in using rocks to make paint. You heard him right. He uses rocks to make paint. Sounds kind of strange. But when you think about it, rocks have a lot of different colors. And if you grind them up into dust and then add water and something kind of sticky, you've got a primitive paint. Here's how Nick does it.

Here I've got a collection of rocks from my recent travels. These ones are kind of special actually. These ones are from Ireland. I've got some white rocks that are basically chalk. I've got some kind of rusty orange rocks. I have some bluish green rocks which are actually very special because blues and greens are really hard to come by in the mineral world. I have some kind of burgundy maroon colored stones.

even a black, kind of muddy, muddy black stone. And then a really special green, which is some kind of marble, marbly green, light green. I'm going to make a pigment with the bluish green rocks. I'm going to gather them up and put them into my granite mortar and pestle. And I'm going to put one or two in, and then I'm going to start smashing them. So a mortar and pestle is basically, imagine a bowl, like a stone bowl. That's the mortar. And the pestle is...

little handle thing that I'm gonna it's like almost like a little hammer stone that I'm gonna use to smash my little stone in that granite bowl. So here it is. First thing I do is I smash that rock into a bunch of little smaller rocks and then I'm gonna start grinding it. So I'm gonna do that as long as it takes to get a nice powder. Right now we're looking at kind of a light greenish blue. It's almost like a pastely

pastely green color. That's a really nice kind of rustic pigment as it is and we could use it as a pretty fun paint. I'm going to get a jar. Any old jar works. It's nice if it has a lid. And now I'm going to carefully pour my pigments into that jar. I don't want to spill any of it because it's pretty precious stuff. The next step is to add a little bit of water to it.

i have water in another jar and i just want to use enough water just enough to cover the pigment i don't want to put too much water in just a little bit and now the next step is to put the lid back on and i'm going to shake this up really vigorously and now what's happening as i've stopped shaking this immediately

The larger of those pigment particles, the heavier ones, those are settling down to the bottom of the jar first. All the fluid that's still kind of floating around with pigment, I'm going to pour that into a different jar and save it. And then from there, you've got a nice pigment and you can add another ingredient, which is your binder. The job of the binder is to keep the pigments suspended in the solution.

As you're mixing it with water, that's your solution. And you need a binder to keep those little particles floating in there rather than just having them all settle to the bottom. So the binders can be egg, they can be glue, they can be honey, they can be a wide variety of things. Oil, if you want to make oil paint, your binder would be some kind of oil.

So it can be as simple as that. It can really be as simple as spitting in it. And saliva happens to be a wonderful binder. It's kind of perfect, actually. It's got the right kind of enzyme cocktail and the right consistency. It just happens to work wonderfully. And that's definitely something that people have been doing for a long time. For this particular batch of paint, I'm going to use egg. It'll basically be an egg tempera paint.

And you can use the white of the egg, but it gets kind of goobery or snotty, if you will. So I really enjoy using the yolk much, much more. So I'm going to just crack open the egg. I've got a bowl I'm going to crack it on. Okay, and I've opened the egg, and I'm going to just kind of carefully pour the egg back and forth.

from one half to the other and let the egg white kind of drip away. Now I'm going to pour the egg yolk contents out into the jar of pigment. Now the trick is just to mix them all together and then I'll work with it and see if I like it. And if it's too thin, I'll add some more pigment. And if it's too thick, then maybe I'll put in another egg.

It's ready to work with. So get yourself a piece of paper or some other surface to paint on and give it a go. Nick says one of the cool things about making paint from rocks is that you never quite know what color you're going to get until you actually start painting. Have fun with this. Go out, find rocks that look interesting to you or look cool.

See if you can smash them. See if you can grind them into a powder. Some rocks are going to be really hard to do this, maybe not worth your effort. And then you're going to find some rocks that you can basically draw with them like they're a piece of chalk. And those ones are going to be really...

They're very easy to make paint with. So you get to do this really cool scavenger hunt when you're trying to make paint. The disclaimer is you're going to start bringing rocks home. And if you already thought rocks are pretty and you had other reasons for collecting them, this is just going to make that worse. Tell your parents now that you need this rock because you're going to do something cool with it and it's worth it.

So there you go, a lesson in how to make your own paint from rocks. Now that you have some tips, what kind of art will you make? Nick Netto makes a lot of other art materials too, not just paint. While we were in his studio, he showed us a few other things he's made over the years. These are a collection of pens that I've made from various woods.

Bamboo is a really nice material for making pens. Turkey feathers or swan or goose feathers make really wonderful pens. Let's see. One of my favorite things to work with is charcoal. And charcoal is an ancient pigment, an ancient black pigment. People have been making artwork and drawings with charcoal for thousands and thousands of years. And these are willow twigs and grapevine twigs that I've charred into really nice charcoal drawing sticks.

Then there's crayons. You can make crayons from beeswax. You can use those same pigments that we are processing for paint and we can mix them with beeswax to make crayons. Then there's paint brushes. Paint brushes are really fun to work with, fun to make. I've got a roll of paint brushes here, some of my wild crafted paint brushes. Some of this one here is goat fur that one of my pet goats donated to me. You know there's horse hair is a nice material for making paint brushes.

This one here is actually bear fur from a bear, unfortunately a young bear that had been shot by a beekeeper because the bear was getting into the hives. And my mom, knowing what kind of person I am, she salvaged the hide for me. And I got a piece of, a little bit of that fur from the hide and I've used it for a few paintbrushes and worked on a nice painting of a bear with this paintbrush.

Then of course deer fur. Deer are pretty, you can just find deer fur in the woods oftentimes where they're bedding down or of course occasionally you'll come across a roadkill deer or you might hunt deer and you can definitely make paintbrushes with their fur too.

Once he's got his materials, Nick thinks about where they came from when he makes his paintings and drawings. I really like to honor those creatures or those things or those places that provided me with the raw material to make my tools and feature them in my compositions.

There's a painting I did with ink I made from acorns from red oak trees. And so, you know, I've done a lot of paintings and drawings with that red oak ink, the acorn ink of red oak trees. There's a painting I did of a coyote in the Grand Tetons, and I used a paintbrush that I made with the fur of a coyote that I'd found. It was a roadkill coyote, unfortunately. Um,

I'm working right now on a painting of a coconut palm tree from my travels in the Caribbean. I made the ink while I was there from the shells of charred coconut and made a really nice black ink. And so I'm using that ink to draw and paint the coconut tree. It goes on and on, using pens from turkey feathers and drawing turkeys with them. I don't do that with all of my work, but the first few pieces...

that I do with a new material, I really like to take the time to honor the source of that material. If you'd like to see some of the cool materials and artwork that Nick Netto makes, you can find them at butwhykids.org. And if you decide to make your own paint, send us a picture of the paintings you make with your homemade pigments. Coming up, we're going to learn what makes tape so sticky and how erasers work.

This is But Why, a podcast for curious kids. I'm Jane Lindholm. My name is Emerson. I am six years old. I live in Westwood, Massachusetts. I really enjoy this podcast, and my question is, how do erasers erase? And here's a question from Adele. How does a pencil's eraser erase its own lead? When you hear someone talk about the lead in a pencil, Adele, it's actually a little bit misleading. The stuff inside a pencil is not lead.

It's a mineral called graphite. When you write on a piece of paper, you're actually rubbing graphite particles onto the paper. I have one right here. I'll draw something. This is a dog holding a banana in its mouth. Wait a minute. Dogs don't eat bananas. They chew on bones. I'd better erase that banana. I'll just turn this pencil over and use the eraser to get rid of it.

And just like that, it's all gone. What happens when I rub that eraser over my drawing is that the eraser is rubbing those graphite marks right off the paper. Now, friction is what happens when two surfaces rub together. If you've ever skinned your knee on the pavement, you've seen what can happen when two different surfaces are rubbed together. That's kind of what's happening to the paper from the eraser.

Now, erasers are made of a lot of things, but the most common ones, the pink ones at the end of your pencil, are made out of synthetic rubber. Synthetic means it's man-made, so this kind of rubber comes from a factory. Organic rubber actually comes from a rubber tree. So the synthetic rubber in your eraser also has some other things added to it to make it more scratchy, and some things that make it smooth, like vegetable oil. And then it's dyed pink. I'm not sure why.

So when you rub your eraser against the paper, the stickiness in the rubber lifts off the graphite particles from your pencil. But the soft part of the eraser makes sure you don't just tear right through the paper.

By the way, one of the reasons why you can't erase pens as easily is because the ink in the pen actually kind of goes into and is absorbed by the paper. So you'd have to rip the paper to get the pen marks off, but the graphite is on top of the paper, so it can be rubbed off.

Erasers have been around for a couple hundred years. Some sources say that before that, people actually used pieces of bread or even scratchy rocks to erase their mistakes. Why don't you give that a try and let me know how it works. But maybe don't do it with your homework. Here's another question about something you might use a lot of. Hi, my name is Simon.

I am five years old, and I live in Chicago. My question is, how is tape sticky? My name is Iris, and I live in Salem, Massachusetts, and I'm five years old. And my question is, why is tape sticky? Why is tape sticky?

Sticky tape, sometimes called scotch tape or cellophone tape, and other tapes like duct tape and masking tape, started being developed about a hundred years ago. I have some here in the studio with me. It's super handy for things like taping my script to my forehead. Uh, except now I can't read what I'm supposed to say.

Anyhow, before sticky tape was invented, adhesives or glues were mostly used to fix things and hold them together. But you pretty much had to be sure that you wanted those two things to be stuck together forever, permanently. So what if you wanted to be able to stick something to a window or a door or something like that and then pull it off? That was some of the motivation behind the creation of tape.

The sticky stuff on a piece of tape is usually made up of chemicals. Sometimes rubber, like what we were just talking about with erasers, is one of those chemicals. These chemicals have adhesive, or sticky, properties.

But the way tape actually works is that the chemicals kind of act like both a liquid and a solid. They have viscoelasticity. Hmm, that's a big word. Viscoelasticity means that it has some of the properties of a thick liquid, think of molasses or maple syrup or honey, and some of the properties of something that is elastic or stretchy, like a rubber band.

When tape is pressed against something, like my forehead, or more likely a piece of paper, it sticks to the surface because it kind of wets the surface a little bit and that helps it stick. And it then resists separation when you pull on it. But those bonds aren't permanent, meaning you can pull it up and move the tape.

Of course, it's easier to pull tape off a window or off my forehead than it is to pull tape off a piece of paper because the paper itself is likely to rip, while my forehead, luckily, stays in one piece. And some tape is made to be really sticky, and other tapes are made to be less sticky. It has to do with what chemicals are put on the sticky side of the tape.

For example, have you ever heard of a post-it note? It's usually a little square piece of paper, sometimes yellow, that you can write a note on. Like, hey mom, we need to buy more cookies.

And then you can stick it on a wall or on the fridge and the note will stay there. But then whatever adult you wrote that note to sees it and thinks, oh no, there is no way we're getting more cookies. And they can just lift the note right off the fridge, crumple it up and throw it into the recycling bin. Because post-it notes are designed to be only a little bit sticky.

So, the science behind tape is actually pretty complicated, but that's a little bit of how it works. Now, if you have a question that's kind of sticking to your brain and you'd like us to find an answer, have an adult record you asking it and send it to But Why. It's easy to do on a smartphone using voice memos or voice recorder. Those are free apps that usually come with the phone. Be sure to tell us your first name, how old you are, and where you live.

If talking is difficult or uncomfortable for you, you can always have an adult send us an email with just the text of your question. You can send the email or the sound file to questions at butwhykids.org. But Why is produced by me, Jane Lindholm, and Melody Beaudet at Vermont Public Radio. Our theme music is by Luke Reynolds. We had additional music today from Pottington Bear.

We'll be back in two weeks with an all-new episode. Until then, stay curious. From PR.