Project silicon sphere
The original kilogram has become a good 50 micrograms lighter. The loss of 50 micrograms may be tolerable in everyday life, but in industries that thrive on precision, even 50 millionths of a gram is significant. Where the mass has evaporated to is a mystery. The most probable cause is the outgassing of hydrogen.
Together with the Physikalisch-Technische Bundesanstalt (PTB), the company HÄFNER from Oberrot, in cooperation with J. Hauser GmbH & Co. KG, Solms, managed to produce the roundest spheres in the world on an industrial scale and to offer them on the global market with the extensive, partly newly developed special accessories for handling, storage, transport and cleaning.
The background to this highly complex development is the renewal of the internationally agreed system of units (SI), which can be classified as revolutionary. Until May 2019, the "original kilogram" was considered the standard of all things for 130 years; today, the definition is based on invariable natural constants (Avogadro constant / Planck constant).