Buzz
Ketchup lovers are all too familiar with the frustrating challenge of getting that condiment out of the bottle, especially if it’s a glass one. If you've ever wondered why this seemingly simple task is so difficult, the answer lies in the nature of ketchup itself: it’s a non-Newtonian fluid.
To understand the physics behind it, check out the link below for an illustrated breakdown. In short, ketchup doesn’t behave like typical liquids. Most liquids—such as water or olive oil—have a constant viscosity, meaning they resist flow in a predictable way. These are called 'Newtonian fluids,' and they pour smoothly. Ketchup, however, is different.
Non-Newtonian Fluids, like ketchup, have viscosities that change depending on external forces. Their flow is influenced by shear rate. Some are shear-thickening liquids, meaning they become thicker when stirred. Ketchup is a shear-thinning liquid, meaning it becomes less thick with agitation (like tapping a glass bottle).
This is why you need a force like tapping the bottle or using a knife to get it out. However, for a smooth and mess-free ketchup experience (without watery drips), avoid glass bottles and opt for squeeze bottles with a 'flower petal-shaped opening.' This design helps trap the remaining ketchup inside, preventing leakage while dispensing.
Artwork by Lucas Adams.
