Vacuum Flask

insulation · heat science · invention

Stops heat transfer. A vacuum flask has two glass or metal layers with almost no air squeezed between them. Since heat travels through air by moving molecules around, removing the air creates a barrier that slows down how fast your hot chocolate cools down or your juice warms up.

Invented by James Dewar. A Scottish scientist named James Dewar created the vacuum flask in 1892. He wanted a container that could keep things at the same temperature for as long as possible, and his clever design worked so well that people still use the same idea today.

Keeps drinks dry outside. When you pour something cold into a vacuum flask, the outside stays completely dry. Regular bottles get wet with condensation because warm air hits the cold surface, but the vacuum flask's insulation prevents this from happening.

Connected at the neck. The two flasks are only connected where the liquid goes in and comes out. This narrow connection means heat has almost nowhere to escape, so drinks stay at their perfect temperature whether you want them steaming hot or ice cold.