in 1899 Richard Küch succeeded in melting rock crystal, forming quartz glass, to be used in sunlamps from 1906 on
Richard Küch
1860 - 1915
In 1890 physicist and later chief developer Dr.
Richard Küch (1860-1915) joined the company led
by his schoolmates Heinrich and Wilhelm Heraeus
(1860-1948). In 1899 Küch succeeded in melting
large quantities of rock crystal in an oxyhydrogen
compressor, forming pure silicon dioxide (SiO2) or
quartz glass. A number of qualities made quartz
suited to all kinds of laboratory equipment: it was
transparent to ultraviolet rays, had a high
temperature resistance, could withstand sudden
temperature changes and was resistant to most
acids. In 1904 Küch invented the sunray lamp, made
of mercury and quartz glass. Mercury vapour arc
discharge lamps were initially used for lighting large
spaces, such as streets and halls, until more
powerful metal-wire lamps replaced them. Küch had
noticed that close proximity to the discharge lamp
caused burns to appear on his face and hands, an
effect attributable to the ultraviolet light that
penetrated the quartz glass. The permeability for ultraviolet radiation and a
temperature resistance as high as 1000 degrees Celsius enabled mercury vapour arc
discharge lamps made from quartz glass to produce a much higher yield of medically
effective light in the wavelength range between 400 and 280 nanometers.