Keeping Coffee Hot - Is the Secret in the Lid or Mug Construction?

I became convinced that simply putting a lid on a cup of coffee, regardless of the cup material, would keep coffee hot for an extended period of time. I put it to the test here, putting a vacuum-insulated mug against a ceramic mug both with and without the cover. In the end I found a $12 alternative to an Ember mug. The video I reference at the beginning, where I tested several mugs for their effectiveness at keeping coffee hot, is at https://youtu.be/xb1uKjeGkKU.

Видео Keeping Coffee Hot - Is the Secret in the Lid or Mug Construction? канала Matt Burns