French-fry lovers of the world can breathe a collective sigh of relief, because scientists have finally figured out the best way to get ketchup out of the bottle. Dr. Anthony Stickland of the University of Melbourne explains his findings in the university's website, Pursuit, by accepting that ketchup isn't a liquid, but rather a "soft solid," like toothpaste.
Many condiments, like mayonnaise, are also soft solids and these substances do not follow Newton's law of viscosity. You see, the tomato solids are suspended in liquid and in order to get the ketchup out of the bottle, the would-be diner must overcome the ketchup's physical strength that comes from the solids touching each other. That strength resists motion, which is why it's occasionally difficult to get ketchup out of a glass bottle.
Still confused? Here's how to get the job done.
Stickland says rheology, which studies these soft solids, "explains all the phenomena seen in tomato sauce (ketchup) bottles and provides the answers to the perennial sauce question, which can be tackled in three main steps."
Step 1: Shake it up, baby.
The solids in the ketchup may have settled to the bottom, leaving a watery film on top (the dreaded ketchup water that comes out before the ketchup at so many backyard barbecues). Or some of the condiment may have settled in the narrow neck and dried out. Either way, shake things up (with the lid on, of course) to get everything homogenized.
Step 2: Flip it upside down.
Get all the good stuff in the neck of the bottle by flipping the bottle upside down and then, "thrust downward at high speeds, accelerating both the ketchup and the bottle."
Step 3. Tilt and pour.
Turn the bottle upright again, remove the lid, and start tilting downwards. If the bottle isn't full enough to pour out on its own, a few firm whacks on the bottom of the bottle should get things going.
Chances are you were doing some (or all) of these steps anyway, but now it's scientifically proven you were on the right track. And hey, if this is all just a little too involved for your weekend burger, you can always invest in a ketchup squeeze bottle.