In 1819, Fresnel wanted to validate his theories, and for this he needed to create a prototype. He contacted François Soleil (1775–1846), an optician who had already worked for François Arago. Soleil manufactured opera glasses, prisms, chambres noires, microscopes and vernier glasses. He was very much a part of the small world of scientific instrument-makers who worked for the members of the Academy of Sciences. His workshop was located in Paris at 21 Passage Feydeau. Fresnel's request was a sensitive one, as it went completely against the types of lenses produced by opticians, who normally polished very small concave or convex lenses that were never larger than 10 cm across. Fresnel, on the other hand, wanted rings of lenses up to 90 cm wide. Moreover, Soleil worked exclusively by hand in his small shop, and milling Fresnel's lens required the use of a steam engine in a large workshop. Finally, opticians worked from very small blocks of glass or crystal, whereas a Fresnel lens weighed 80 kg. Between 1819 and 1823, Soleil and Fresnel completely transformed the world of large-scale optics with the use of polishing lathes, glass moulded in cast-iron moulds and workshops for assembly and for mechanics. These technical requirements gave rise to the profession of lighthouse lens manufacturer – a specialty that was nearly monopolised by French firms up until the twentieth century.