What makes whipped slime stretchy?

The PVA glue in your mixture contains millions of long molecules called polymers.

You can imagine these polymers as long, flexible chains. Before the activator is added, the chains can move and slide past one another quite easily, so the glue can still flow.

The shaving cream adds millions of tiny air bubbles, making the mixture feel lighter, softer and fluffier.

But it still isn't slime yet.

What does the activator do?

The borax solution acts as the activator.

When it is mixed into the glue, it begins creating connections between the long polymer chains. Scientists call these connections cross-links.

Instead of the polymer chains moving independently, they become joined together to form a flexible network.

That network is what transforms your runny mixture into stretchy slime.

Why does the slime change as you add more activator?

Adding more activator creates more cross-links between the polymer chains.

With only a small amount, the slime may remain very soft and sticky because the chains can still move around easily.

As more cross-links form, the slime becomes firmer and holds its shape better.

But there can be too much of a good thing. Too much activator can make the slime much firmer and less stretchy.

That's why changing the amount of activator can completely change the slime you create.

Why is whipped slime so fluffy?

The secret is the shaving cream.

Shaving cream is a type of foam containing lots of tiny pockets of gas trapped inside a liquid mixture.

When you mix it through the slime, many of those bubbles become trapped within the polymer network.

This gives whipped slime its soft, fluffy texture and makes it feel very different from ordinary slime.

Scientists Say…

Slime is a great example of how changing the structure of a material can change its properties.

By changing the amount of glue, shaving cream or activator, you can investigate properties such as stretchiness, firmness, flow and fluffiness.

Materials scientists do something similar when they design new materials. They change ingredients and structures, test the results and look for a combination with exactly the properties they need.

Curiosity Spark

You created whipped slime by trapping tiny air bubbles inside a stretchy polymer network.

What would happen if you changed how much shaving cream was trapped inside your slime?

Would it become fluffier, stretchier, softer — or something completely unexpected?