Science at the Library: Liquid rainbows

Hi, my name is Sam and I work at the National Library of Australia. 

The Library is located in Canberra on the beautiful lands of the Ngunnawal and Ngambri people. 

The National Library of Australia pays our respects to their elders past and present, and through them to all Australian Aboriginal and Torres Strait Islander peoples. 

Today we have a fantastic and colourful experiment for you to do at home with the team from Fizzics Education. 

Before we head there, we're going to explore some of the truly amazing old books and beautiful ways artists decorate the covers, bindings, papers and edges of the books. 

It's less common these days, but the art of marbling paper was a common sight on books, ledgers (the old books used in businesses), diaries, and even money in the past. Types of marbling have been used for over 1000 years. Artists from across the world including China, Japan, Afghanistan and many European countries developed their own unique styles across the centuries. 

Marbling was used both as an art form and as a form of security because each marble pattern was unique. If a book was stolen, it's marble pattern could be easily identified by its owner. 

When it comes to books, marbling is often on the front and end pages. Some books also have it on the edges of the paper as well. There might be swirls, circles, jagged lines or beautiful organic shapes. 

Marbling gets its name from the fact that it sometimes looks like marble. 

There are several techniques that can be used to make the patterns, but the basic principle is always the same. Colored dyes, all paints are carefully applied to the surface of water. You must do this very carefully to make sure that the surface tension of the water stays intact. 

Different processors use different substances to help with this. In the past, types of seaweed and algae were used, whereas today things like oil paints and PVC are used. 

Once all the colors have been added, the artist can then create the patterns by mixing and moving the colors around the surface of the water with things like pins, straws or blowing on the surface of the water and even by using other chemicals to push the colors around. 

Let's hand over to our friends at Fizzics now who have a simple experiment that you can try at home that explains how surface tension works and what happens when it's broken. 

Remember, always ask first before you do any kind of experiment and always have an adult that you trust around to make sure everything is safe. 

Ben: This experiment is really powerful and I must say it's really interesting 'cause not only can you do it with kitchen chemicals, it shows quite a lot about chemistry. 

So let's go have a look. 

What we need is a plate of full cream milk. 

Any form of detergent and some food coloring. 

Really easy to work with, so I've got here my full cream milk. Now you could try, after this experiment, trying skim milk or any other version of the many types of milk you can buy at the stores. Now you notice I have not put my milk very deep in my plate. 

It's very important we just want to make it nice and shallow to get the effect that we want to see. Get your food coloring. Now, this is a temptation to add too much food coloring, just a drop. 

Maybe two, we don't want too much, so I'm going to do green over here and here. 

Put my red here as well, you could choose another colour. 

It's up to you. 

By the way, if you don't have all the colors, that's not a big deal. 

In fact, you can see this effect with just one colour, but today I'm going to use three 'cause hey, why not now? 

Here's the thing. Do you notice that the colors have not spread out through the milk much and the reason why is the fat in the milk is in the way. 

The water is the only thing that brings the free coloring around. 

It's the food coloring only follows where, the water is. 

They kind of work together, in fact. 

What if we break up that fat using a small amount of detergent? 

I'm going to use a little cotton swab and put a little drip in the center and I must say it's really fast, Are you ready? 1, 2, 3, dripping in one. 

Now, if you're doing this at home, did yours do the same?

I must say it really doesn't matter which type of full cream working years, as long as it's full cream milk. 

Now notice there's more than just the colours shooting outwards. 

What was happening? My colors, like yours, start out and then they start mixing. 

Look, there's one there starting to mix. 

There's another one there, mixing now, then they're mixing. 

It's happening all over the place, in fact. 

This keeps on going without me adding anymore detergent it keeps on happening. 

So why is that the case? 

Now think about when you use detergent to wash the dishes. 

I hope you help wash the dishes, it is a very important skill, but here's the thing. 

When you use detergent to wash the dishes, it helps break up the fat that's on the top .

Now, that's exactly what's happening in our milk. 

Our milk has fat in it and as the detergent breaks up the fat, food coloring rushes into the space where that's broken up because the food coloring follows the water and the water rushes into where the tensions being broken up, but here's a thing. 

That's not why we first saw the colors moved outwards. 

The reason why we saw that was a bit like this. 

Everyone get your hands like that. Now pull outwards. You feel like tension in your fingers and your fingers let go. They shoot outwards right? 

At the top of your liquid, at the top of your milk, there are forces those molecules of your liquid in this case, our milk, they're holding tight like that as well. 

Really tight, really wisdom strong bonds. 

They've got tension. 

Scientists call this surface tension. 

Now that surface tension pulling sideways quite hard and when we added detergent into our milk, it barked attention and so the colours shot outwards. 

So let's find out. 

What happens if we add more detergent into our milk? 

Does it change the colors? 

So I'm going to add some detergent here and here. 

I'm seeing a little bit of a change. There's some changes happening over this way and changes happening over this way. There is starting to be a bit of a marbling effect happen now as these fat gets broken up, the food color is going to mix more and more and more through the milk and we're going to get different colors. 

So what colors will you make if you have blue, green and red? You'll make different colors to mine 'cause I got pulled green, red and yellow. What colors will you have and you know what? You can do paper marbling at home. And that's a lot of fun and something you can definitely check out. 

What an interesting pattern that die creates when adding detergent. 

You can also try a similar experiment by adding a small amount of oil to a bowl or plate and add drops of food coloring on top. 

Use a toothpick to swirl the colors around, I wonder what might happen if you add. Water to it. Or maybe detergent? 

Thanks for watching. Happy experimenting.