Don’t spend time waiting for the temperature to drop to the dew point; use this convenient demonstrator instead. Fill the nickel plated cylinder with alcohol, then squeeze the attached rubber bulb to introduce air into the system. Evaporation occurs, causing the temperature to drop until condensation forms on the outside of the cylinder. It comes with a 12″ red alcohol thermometer, -20 to +110°C. Alcohol, required, is available separately. Cylinder length: 12″.