Lots of people know not to blend hot liquids in a blender, but not everyone knows why - except that you'll burn the hell out of yourself. The reason is that the blender blends everything inside of it together so hard, so fast, and so thoroughly that if you're starting with anything liquid, it almost instantly gets turned into sort of a foam, as all the air and all of the liquid in the container become one over the space of about a half of a second. The thing is, not only does all of that air get mixed in with the liquid -- over the course of that same half second it takes for that to happen, every bit of that air also becomes EXACTLY THE SAME TEMPERATURE as the liquid. In the case of hot vichyssoise, that's often around 200 degrees. The rest is simple chemistry: Because air that hot takes up more space than air at room temperature, the second you turn the blender on, your two cups of steaming vichysoisse stay the same, but the 3 cups of air in your blender instantly turn into about 3 3/4 cups -- easily enough to instantly blow the blender's lid off -- and, in this case, blast scalding vichyssoise all over you and your kitchen. Most everyone who has this experience only does it once. For those who learned the lesson making something that sticks to the skin as well as 200 degree Vichysoisse (as did I), they NEVER make the mistake a second time. And they become eager to help others avoid it.
