Have you come across the viral TikTok or Insta Reel video where cocoa powder dipped in milk gets wet and suddenly becomes dry again, when poked with a toothpick? If you wondered it was some trick of the camera or fake milk/cocoa, then you are wrong. As eloquently explained by the YouTube science channel, ‘The Action Lab’, it is the hydrophobic property of cocoa powder that results in this magical trick. But if it really is hydrophobic, i.e. water repellent, then how does it create the delicious hot cocoa we love?
In his latest explainer, YouTuber James J. Orgill chose the "cocoa dipped in milk turning into dry powder again" trick. He replicates the viral trick in a jar of milk first. Just like the viral videos, he takes a spoonful of cocoa powder (stacked high in a heap) and dips it whole in the milk. The key here is to dip the whole spoon straight down so that the heap of cocoa is intact and not to mix it/stir it with the liquid. After a few seconds, you can lift up the spoon gently.
What you will see is a heap of ‘wet’ cocoa powder. Then, take a toothpick and swiftly poke at the surface. Like a magic illusion, the surface seems to break and revert in its dry, powdery form.
He tries the move several times and calls it, “it’s like you’re popping a balloon or something.”He repeats it in water to get the same results.
Cocoa, a mildly hydrophobic substance, repels water and attracts air. When dipped in milk, it forms a kind of air bubble around it. Now, the outer layer of cocoa, which has started to mix with the water, gets wet. But, the air bubble protects the rest of the pile from getting wet. Once we poke it, the surface tension breaks, releasing the air bubble and revealing the dry cocoa inside.
Orgill repeats the experiment with an extremely hydrophobic substance called lycopodium powder. As he sprinkles the powder on water, it stays on the surface. When he dips his finger in the water, the powder coats his finger and his hands remain dry. But in a cool vacuum experiment, Orgill shows this powder loses some of its hydrophobia in absence of air.
Watch the whole experiment here:
Uploaded on March 15, the video has raked in nearly 1,30,000 views with 9000 “liked” on the video-sharing platform.