MIT scientists have cracked one of the great universal mysteries: how to get those last few drops of ketchup out of the bottle.
Researchers from the Varanasi Group at the famed university have used to develop a proprietary non-stick coating called LiquiGlide, as seen in action here:
Because the coating's made from food materials, it's non-toxic, the researchers claim.
"Even if you scraped off the coating with a knife and ate it, it would be completely harmless and flavorless," LiquiGlide's creators say.
Stubborn condiments aren't just frustrating for consumers; they're also a big source of food waste. LiquiGlide's makers think they can help cut down on the amount of food that gets thrown out, as well as reduce the need for petroleum-based plastics that go into the bigger squeeze bottles.
The real question, of course, is what secret ingredients go into a stress-free ketchup pour?
"I can't say what they are," MIT researcher David Smith told Fast Company, "but we patented the hell out of it."
You probably won't see LiquiGlide-coated bottles at the supermarket for a little while, so for now you're stuck smacking, tapping and scraping to get at the dregs of your ketchup bottles.
One reason for ketchup's uncooperative behavior is that it is what chemists call a "thixotropic fluid," a category that also includes certain types of clay and yogurt. These kinds of fluids are thicker at rest, but become thinner when shaken or stirred. When ketchup is sitting in the bottle, its molecules are more entangled. Once you shake the bottle, smack it repeatedly, or scrape at the insides with a butter knife, a physical force called "shear stress" breaks up the bonds between molecules and allows the ketchup to flow.
But ketchup itself is just one part of the equation. The other is air.
In order for ketchup to get out of the bottle, air has to come into it. Sometimes it's hard to get air in past a wall of coagulated ketchup in the neck of the bottle, hence the smacking and shaking to make the condiment flow more easily.
Scientists have often been called upon to solve condiment conundrums. At a question-and-answer site called Ask the Van, University of Illinois at Urbana-Champaign physicist Tom Junk describes his ketchup-pouring solution:
"The best technique I've found through trial and error and a little bit of sense is to tip the ketchup bottle at about a 30-degree angle with respect to the horizontal, the neck pointing at my hamburger," Junk says. "At the end of a downwards shake, I make sure the acceleration in the upwards direction is large, stopping the bottle's downward motion, helping to dislodge the ketchup."