A flask and a bottle are used by Dr. Vincent J. Schaefer, General Electric weather scientist, to make indoor clouds. He introduces moisture and a little smoke into the flask, then raises the pressure slightly by squeezing the bottle. This heats the air and permits more water molecules to "dissolve." When pressure is reduced by releasing the bottle, the air cools forcing water molecules to condense on smoke particles to form a cloud. A similar process forms clouds in the sky.

General Electric Company1953-01-30