A violation of the second law of coffee dynamics?
February 21, 2010 2:35 PM Subscribe
What phenomenon of coffee physics or fluid dynamics is going on here
posted by escabeche to science & nature (14 answers total) 13 users marked this as a favorite
This is a tall glass mug of hot coffee, about five minutes after adding a glug of skim milk. I didn't stir it. I could understand it if the milk were distributed uniformly around the coffee, or if there were a smooth gradient of milk density. But instead there are four distinct bands with sharp transitions between them, going from milkiest at the bottom to least milky at the top. I've now seen this happen three times, always at Steep and Brew. Of course this phenomenon could only be observed in a transparent container; but I don't believe I've seen it happen in a pint glass. Does the striation have something to do with the curvature of the mug? What could possibly be maintaining the sharp boundaries between the different layers?