Physics says this is the best way to cool down hot coffee

LIKE MANY PEOPLE, I enjoy getting a nice cup of coffee. Not that silly sugary stuff like a double-whip, non-fat, vanilla bean, espresso, iced with a twist of lime. No, I get plain old boring black coffee. But there’s a problem: It’s almost always too hot to drink right away. When life gives you coffee that’s too hot, you must find the best way to cool it.

I have two methods to cool off my coffee. Method No. 1 is to remove the lid (coffee usually comes with a lid so you don’t spill it). Method No. 2 is to leave the lid on, but occasionally blow over the little hole that you are supposed to drink through.

Which method works the best? Let’s find out with a simple experiment. OK, before doing that, I need some things. First, coffee cups. That’s easy, just drink coffee and save the cups. Second, I need some temperature values. What is the starting temperature of coffee? It seems 80°C is a common coffee temperature. But what temperature do I like my coffee? Based on my personal preference, I find that 64°C is quite nice.

Now for an experiment. I will pour hot water (the assumption being it is similar to black coffee) into three cups.

  • Cup 1 has a lid and that’s it. This is your standard cup of coffee.
  • Cup 2 has no lid.
  • Cup 3 has a lid, but I am going to blow on the opening.