Pyrometer

Josiah Wedgwood had been born into arguably one of the most exciting eras in English history - an age of enquiry, discovery and experiment. None of the superb advancements in ceramic production would have been feasible in the 18th century without Josiah’s pioneering activities to produce a thermometer which could measure high temperatures inside the kiln. Prior to the successful production of Wedgwood’s thermometer, (or pyrometer as it was also known), the kiln man was always the highest paid workman on the factory because it was purely by his skill and judgment that wares were successfully fired. Josiah had experimented since 1780 with the construction of the thermoscope, matching fired clay cylinders with those fired at known temperatures ranging in colour from buff to red indicating respectively low to high temperatures, but later he turned to measuring the shrinkage of clay using an upgraded pyrometer which he devised. As porcelain shrinks when fired, the shrinkage of small pieces of fired porcelain could be used to measure kiln temperature when placed in a gauge. Josiah Wedgwood even invented his own temperature scale – degrees Wedgwood.

Wedgwood’s development of this thermometer revolutionised the industry and for his achievement James ‘Athenian’ Stuart, the celebrated architect, proposed Josiah for election as a Fellow of the Royal Society. On 9 May 1782 Wedgwood read his paper on, ‘An attempt to make a Thermometer for measuring the Higher Degrees of Heat ... up to the strongest Vessels made of Clay can support’ and he was awarded the highest scientific accolade in the country by election to the Royal Society.

Images

A brass Wedgwood pyrometer, © Wedgwood Museum

A brass Wedgwood pyrometer
© Wedgwood Museum