I love it when failures lead to success. I put some hot cocoa into the microwave to make it even hotter. For a bit too long. And the result was boiled over cocoa. How sad. But as I was removing it and getting ready to chuck it away I saw a way cool effect. The overheating had formed a skin on the top of the cocoa (the milk's proteins and fats get up close and personal as the temps rise and form this skin) and the skin let the temps zip up (which led to the overflowing). But now, with much of the cocoa having ejected itself from the glass, what remained was a very hot cocoa mixture underneath a tight fitting (and flexible) skin.
Well, those who study heated liquids know that they move. A lot. Swirls and upwellings and general to and fro motions. All invisible to the naked eye. But when there's a tight-fitting skin we suddenly can see the previously unseen. The skin will wrinkle in response to the slightest touch from the roiling liquid in a most fascinating manner. Almost as if it's …. alive!
I didn't think to grab my camera immediately so the skin got a bit harder toward the center, with the more flexible regions near the edges. But, hey, at least I grabbed it eventually!
So – want to know what the secret life of hot cocoa really looks like? This:
it's alive! =O
Aren't the small swirls also being caused by the small air currents brushing against the surface of the cocoa, briefly causing it to cool and contract, before expanding again as it reabsorbs some of the internal heat (thereby losing overall energy/heat)?