Station: [33] M – Measuring with Glass: „Toad“

  • Glasmuseum Wertheim


The reproduction of this glass toad possibly came from a Wertheim Technical College for Glasswork examination project during the 1970s. Galileo Galilei developed the original at the University of Florence during the 17th century. The „Toad,“ makes reference to the more than 60 years of thermometer production in Wertheim. Thermometer glassblowers were the first glassblowers to settle in Wertheim in 1948 in the course of the flow of refugees out of Thuringia. Among them were the thermometer companies Arno Amarell and Karl Schneider that still exist today.


The „Toad“ was designed to be bound to a feverish patient’s arm and was the first verifiable thermometer for measuring fever based on a principle of physics that the density of liquids decreases when temperature rises. This means the buoyancy of the hollow glass balls swimming in the liquid is reduced so that they sink. The higher the body temperature, the more the glass balls sink. If five of the altogether seven balls in the alcohol in the „toad,“ sink, the patient has a fever.


Since the 1990’s the „toad“ has enjoyed a revival in the form of the Celsius, or Fahrenheit „Galileo“-Thermometer, which was originally produced in Switzerland, but later in thousands in Wertheim. The Chinese were also quick to recognise its bestseller potential.