If I order a cup of coffee, usually I just drink it black. Recently, I’ve noticed that if you let a cup of coffee Starbucks sit for a few minutes before you drink it, you can see an oily film on the surface of the coffee.
Oily film on the surface of a black Starbucks Coffee
Does anyone know what causes that? I’ve read that fresh coffee has some natural oils, and they would rise to rise to the top, as the coffee settled. Personally, I’m worried that it might be some chemicals from the cup, that are released from the hot liquid.