Josiah Wedgwood created a temperature meter and a scale based on how much clay shrinks as it heats. 1
The Wedgwood scale (°W) is an outdated temperature scale, which was used to measure temperatures above the boiling point of mercury of 356 °C (673 °F) created by Josiah Wedgwood in the 18th century. The measurement was based on the shrinking of clay when heated above red heat, and the shrinking was evaluated by comparing heated and unheated clay cylinders. The scale started at 580.8 °C (1077.5 °F) being 0° Wedgwood on degrees Wedgwood and had 240 steps of 54 °C (130 °F). His method and the temperature scale were then widely adopted for science and technical applications. 2
Wedgwood used the pyrometer, an instrument that he had conceived to measure the heat inside the kiln and that he had presented to the Royal Society in 1782. It consisted of two rulers mounted on a baseboard. The rulers were half an inch apart at the top and one third of an inch apart at the bottom. One ruler was marked with a graduated scale. Specially designed clay cylinders shrank proportionally to the heat they had been subjected to. They were then placed between the rulers, pushed along until they could go no further and the temperature the cylinder had been subjected to was read off the scale, in degrees Wedgwood. 3
This worked for his pottery business, when for example creating the replica of the Portland vase. 4
See the picture of the pyrometer at Museo Galileo’s virtual museum.