Oozey Oobleck, Gloopy Glue: What are Non-Newtonian Fluids?

What do custard, toothpaste and jam have in common? If you’re wondering what culinary disaster these three items would bring about, let’s just stop you there. What we’re getting at here is that these are all examples of “non-Newtonian” fluids. 

In an ordered world in which liquids behave in a predictable way, some substances simply don’t follow the rules. But what are Newtonian fluids and what are non-Newtonian fluids and how can you tell the difference? 

What are Newtonian fluids? 

First, let’s take a look at Newtonian fluids

You may have heard of Sir Isaac Newton. He was the guy who developed loads of great scientific theories in maths and physics, and one of his themes was describing how “normal” liquids behave. He said that they have a constant flow (or “viscosity” in his words), and this flow only alters when the temperature or pressure changes. 

So, if we take water (a classic Newtonian fluid) as an example. If poured at a temperature range of between 0˚C and 100˚C, it will stay as a “normal” liquid with constant viscosity and will take the shape of that container. 

Examples of Newtonian fluids:

• Water
• Milk
• Orange juice

What are non-newtonian fluids?

Yes, you guessed it, non-Newtonian fluids are the opposite and choose to follow their own rules.  With these tricksy substances, when stress is applied, non-Newtonian fluids change their viscosity.

The four different ways non-Newtonian fluids change their viscosity:

1. Thixotropic 

These are fluids whose viscosity decreases with stress over time. For example, when you stir honey, it gets more liquid the more you stir it. 

2. Rheopectic 

These are fluids whose viscosity increases with stress over time. For example, if you whip cream, it gets harder over time. 

3. Pseudoplastic 

These are fluids whose viscosity decreases with stress. For example, when your tomato ketchup is stuck in the bottle, tap or shake the bottle and it will become more liquid and pour more easily. 

4. Dilatant 

Fluids whose viscosity increases with stress. For example, when you mix together custard powder or cornstarch with water it forms a lovely “oobleck” which, when you touch it, feels weirdly hard, even though it’s fluid. 

And this brings us neatly to the best bit….

How to make your very own gooey oobleck, with Renee:

And if you’re interested in experimenting some more with strange textures, why not try our Sublime Slime box?

With everything from glow in the dark to edible slime, this box is the ultimate slime-lovers experiment kit while secretly learning about fluid dynamics, chemistry and density! This Box includes:

👃 Sticky Snot: Glow in the dark, farting snot…what’s not to love!?

🌈 Thermochromic Putty: Test super cool colour-changing putty in different environments

🍮 Gooey Oobleck (Jumbo/Tots only): Is it a liquid? Is it a solid? This gooey oobleck will make your mind boggle!

🐛 Slimy Slugs (Jumbo only): Slime…That you can eat! Make baubles and strings of slime that are good enough to eat.

🌌 Galaxy Tube (Tots only): Explore fluid dynamics by creating a magical, swirling test tube that looks like you’ve captured a galaxy

⚛️ PLUS a collectable Molymod mini kit! *Jumbo only*