We’ve all poured a soda into a glass only to have it overflow all over the countertop. But if you’re a frequent Diet Coke drinker, you might have noticed that the beverage seems fizzier than others. Well, it is.

Thanks to its viscosity, carbonation bubbles stay more stable making Diet Coke fizzier than Coke.

To fully understand Diet Coke’s fizz, you need to have a basic knowledge of why those bubbles happen the way they do. Diet Coke tends to have low surface tension so the bonds between molecules are weaker and more easily breakable. Why? The ingredients.

Aspartame (you know the stuff that makes your soda artificially sweet) and the preservative potassium benzoate are key ingredients in Diet Coke, and they also happen to be surfactants that decrease surface tension. Pair this fact with the soda’s viscosity.

While you might not think it, Diet Coke has a higher viscosity than regular Coke, and while typically this would mean bubbles have trouble forming, it also means when they do, they’re more stable—aka they pop and dissipate slower. So while the fizz formation might technically be “less” than a regular Coke, it sticks around longer which is what ultimately makes Diet Coke fizzier.

Basically, when you’ve decreased surface tension but elevated viscosity, you get fizz that sticks around longer. Pretty neat, right?

But now that you know how Diet Coke is different than Coke (at least in bubbles and flavor), how is it different than Coke Zero?