Why Is Ketchup So Hard To Pour From A Bottle?

Americans really love ketchup, and not just because it's easily accessible and relatively affordable. From its role as a beloved baseball game condiment to its place as a key ingredient in barbeque ribs, the history of ketchup's rise to popularity is long and diverse. In the late 1800s, when Heinz ketchup debuted their recipe in the now-classic glass bottles, the world was forever changed. Generations upon generations of ketchup lovers underwent the same experience –- struggling to get the ketchup out of that dang bottle. Unfortunately for us ketchup lovers, the condiment is a non-Newtonian fluid, meaning that below a certain point of force, this liquid behaves as a solid.

Sir Isaac Newton discovered that some liquids became more viscous when heated and less viscous when cooled, dubbing them as Newtonian fluids. An important characteristic of fluidity is a liquid's ability to flow, which is where the word 'viscosity' originates. Viscosity, the resistance of flow, classifies liquids like water and olive oil as Newtonian fluids, while non-Newtonian fluids like ketchup and mayonnaise defy these rules, behaving as "soft solids" with viscosity depending on pressure. All of this is a very complicated way to say that although technically a liquid, ketchup is more like a solid until the right pressure is applied, which is why it fights to stay in the bottle.

This beloved red condiment is made from finely ground tomatoes, water, vinegar, sugar, spice, and everything nice, but it's the bits of tomato that make up the majority of its composition. It's this physical connection between the pulverized chunks of tomato that changes its viscosity and makes it more resistant to flow. Although it may feel impossible as you tap and grumble at the glass bottle, there's an easy way to force the ketchup out. Screw the cap back on the bottle, turn it upside down, and shake vigorously. In doing this, you're changing the viscosity of the ketchup, forcing it to behave as a liquid and break its solid composition through force.

Another secret hack, directly from Heinz themselves, is to turn the bottle at an angle and tap the little '57' etched into the neck of the bottle. The combination of the angle and the placement of tapping should force the ketchup to loosen, lower the viscosity, and make it flow. If you have a little more time, and the comfort of your kitchen, you can try placing the glass ketchup bottle into a pot of hot tap water. As the bottle heats up, the ketchup on the inside undergoes thermal expansion and its viscosity changes, making it easier for you to get it out of the bottle once the glass cools. Now that you know this condiment's secret to flowing smoothly, skip the awkward bottle slaps and pour like a pro.