Stirring the Pot: Antoine Baumé, Josiah Wedgwood, Pierre-Louis Guinand, and the Development of Optical Glass

The development of defect-free flint glass for use in telescopes and navigational instruments was a key technological challenge facing European chemists, natural philosophers, and artisans that emerged in the 1750s. In 1805, Pierre-Louis Guinand, a Swiss artisan, invented a fireclay stirrer used to stir molten flint glass to create a homogenous mixture relatively free of defects. In this paper, I show it was not Guinand, but French chemist Antoine Baumé, who first came up with the idea of using a fireclay stirrer. More important, both Guinand and another early optical glass researcher, Josiah Wedgwood, knew of and were influenced by Baumé's work. Baumé's optical glass contributions have been forgotten over the years for several reasons. First, he never promoted his idea of a fireclay stirrer due to the limited support and likelihood of failure for such an artisanal-focused project within the <i>Académie</i>, which stressed theory over practice with regards to glassmaking. Second, glassmakers were hesitant to reveal their trade secrets and sources. And third, until fairly recently, Baumé's unrelenting support of the phlogiston theory led to his relegation as a minor figure in the history of chemistry, and his optical glass ideas fell off the radar of subsequent historians.