Why does heavy cream poured into freshly made coffee go to the bottom and disappear before swirling to the top, but heavy cream poured into old, reheated coffee just settles at the top?

Question

Yes, I use real heavy whipping cream in my coffee. The coffee is made using a Bunn drip coffeemaker. I’ve noticed that if I am drinking a freshly made pot, the cream pours in, sinks to the bottom, and then floats back to the top with this glorious blooming effect. But, if I get up and warm up yesterday’s slops in the microwave, when I add the cream, it just sits on top. I’ve experimented with different warming times/temperatures, but it doesn’t seem to matter. What could be the cause of this mysterious coffee anomaly?

In: Chemistry

Answer 1

Maybe your microwave isn’t heating up the coffee evenly throughout? It could be that there’s a pocket of colder, denser coffee below the surface that’s preventing the cream from sinking. You could try giving the coffee a stir before adding the cream and see if that changes anything?