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of Victoria Street, London, SW1 and Vitreosil Works, Wallsend-on-Tyne, Tyne and Wear
1903 A private syndicate of British businessmen formed The Thermal Syndicate to exploit a process invented by Dr. J. F. Bottomley for producing translucent fused scilica from high purity sand. A works was established in Wallsend and the syndicate manufactured the world's first, commercially produced, electrically fused silica products.
1906 The firm was incorporated as Thermal Syndicate Ltd, with Dr. Bottomley as General Manager.
1909 The trademark "Vitreosil" (taken from vitreous silica) was registered and is still in use today for products manufactured from naturally occurring silica sand or quartz crystal.
1910s The company opened an office in New York. Volume manufacturing of transparent fused quarts products commenced in addition to the previously produced translucent fused silica materials.
1922 Advert for Vitreosil - Revolutionising Gas Lighting. Absolutely Heat Proof. Globes, Cylinders and Mantle Protectors. Specialities for gas shades and electric lighting, comprising mantle protectors, globes, bowls, complete with pendants for indirect lighting. (Stand No. G.17) 
1930s 'Optical Quality' fused quartz was developed, primarily for use in ultra-violet applications.
1939 Vi-Tan ultra-violet home tanning unit (see adverts)
1950s-1970s Thermal Syndicate began production of "Spectrosil", the world's first synthetic fused silica.
In the 1960s they developed a new process for production of fused quartz.
In the 1970s the company began development of new production technology to manufacture fused quartz ingots using a continuous fusion process.
1980s The company changed its name to TSL Thermal Syndicate plc in 1981.
In 1984 the name changed again, to TSL Group plc.
1988 The TSL Group became part of the Saint-Gobain group.