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 joined the company led by his
schoolmates Heinrich Heraeus 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 to illuminate
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.