was that the light output fell off considerably during the lamp’s life-time and
it also varied in damp weather.
9.4 The Tungsten Filament Bulb
With the emergence of these new technologies the carbon filament’s days
were numbered, but they remained in use for some time because they were
cheap. For twenty years however, manufacturers had been looking for more
durable materials for the filaments. von Welsbach’s osmium wire was an
obvious contender and in 1898 he re-directed his research efforts producing
an efficient osmium filament bulb. It was very fragile however and had to be
burnt base up to prevent the hot filament from sagging and breaking. But he
patented it, set up the ‘Auer’ Company to manufacture the bulb in 1899, and
marketed it in 1902. In a further improvement in 1903, Austrians Franz
Hanaman and Alexander Just made a tungsten lamp, tungsten being the best
refractory metal. This was made by depositing tungsten onto a carbon filament. The process was not suited to mass production however, but Hans
Kuzel of the ‘Auer’ was able to adapt the osmium squirting process to
tungsten, and in 1906 the DGA introduced and marketed a tungsten filament bulb under the trademark ‘OSRAM’—from osmium and the German
word for tungsten, wolfram—Koppel owning the mark. When Robert arrived
at the ‘Auer’ in 1909, things had moved on and there was now an obvious
need for a more simplistic production process involving fine drawn tungsten
filament wires, and it was on this problem that Robert began work there in
1909, later moving on to develop methods of bulb exhaustion. Robert’s initial
work on the tungsten ductility problem had some success using a method that
heat treated the brittle filament material, but Osram were not enthusiastic,
probably because tungsten—along with osmium—were not the only contenders in the filament market. In 1903 Dr. Werner Bolton and Otto
Freurlin, head of Siemens & Halske’s incandescent lamp works, developed a
tantalum filament after Werner had found a method of drawing it out into
fine wire. In 1905 the tantalum bulb was launched world-wide, but by 1907
they had developed an even better alloy of tungsten (wolfram) and tantalum,
which was marketed as the ‘WOTAN’ bulb. It was quite successful, in use up
to 1914, and the name is still used today. Tungsten filament ‘OSRAM’ lamps
were marketed in the UK by the British General Electric Company (GEC) in
1906. In 1907 they also marketed Siemen’s ‘WOTAN’ lamp, but the technological advance of ductile tungsten, eventually made it the best option. In
1910, the American William Coolidge beat Robert and the ‘Auer’ to the
9 The Auergesellschaft, Berlin
193
it also varied in damp weather.
9.4 The Tungsten Filament Bulb
With the emergence of these new technologies the carbon filament’s days
were numbered, but they remained in use for some time because they were
cheap. For twenty years however, manufacturers had been looking for more
durable materials for the filaments. von Welsbach’s osmium wire was an
obvious contender and in 1898 he re-directed his research efforts producing
an efficient osmium filament bulb. It was very fragile however and had to be
burnt base up to prevent the hot filament from sagging and breaking. But he
patented it, set up the ‘Auer’ Company to manufacture the bulb in 1899, and
marketed it in 1902. In a further improvement in 1903, Austrians Franz
Hanaman and Alexander Just made a tungsten lamp, tungsten being the best
refractory metal. This was made by depositing tungsten onto a carbon filament. The process was not suited to mass production however, but Hans
Kuzel of the ‘Auer’ was able to adapt the osmium squirting process to
tungsten, and in 1906 the DGA introduced and marketed a tungsten filament bulb under the trademark ‘OSRAM’—from osmium and the German
word for tungsten, wolfram—Koppel owning the mark. When Robert arrived
at the ‘Auer’ in 1909, things had moved on and there was now an obvious
need for a more simplistic production process involving fine drawn tungsten
filament wires, and it was on this problem that Robert began work there in
1909, later moving on to develop methods of bulb exhaustion. Robert’s initial
work on the tungsten ductility problem had some success using a method that
heat treated the brittle filament material, but Osram were not enthusiastic,
probably because tungsten—along with osmium—were not the only contenders in the filament market. In 1903 Dr. Werner Bolton and Otto
Freurlin, head of Siemens & Halske’s incandescent lamp works, developed a
tantalum filament after Werner had found a method of drawing it out into
fine wire. In 1905 the tantalum bulb was launched world-wide, but by 1907
they had developed an even better alloy of tungsten (wolfram) and tantalum,
which was marketed as the ‘WOTAN’ bulb. It was quite successful, in use up
to 1914, and the name is still used today. Tungsten filament ‘OSRAM’ lamps
were marketed in the UK by the British General Electric Company (GEC) in
1906. In 1907 they also marketed Siemen’s ‘WOTAN’ lamp, but the technological advance of ductile tungsten, eventually made it the best option. In
1910, the American William Coolidge beat Robert and the ‘Auer’ to the
9 The Auergesellschaft, Berlin
193