||The original tungsten filament lamps produced by the GEC in England employed sintered tungsten wires, imported from the German Osram company, with whom a relationship had been established some years earlier. As with all lamps having sintered tungsten filaments they were exceptionally fragile, and could only be burned vertically cap-up.
The introduction of lamps having drawn tungsten wire marked a major breakthrough in terms of reducing cost and yielding a more flexible design. As far as the customer was concerned, one of the key features was the lifting of the restriction on burning position. It is interesting to note the "Angle" statement on the packaging, indicating its suitability for operation at all angles. However, the filaments of early lamps, being based on a thorium-doped wire, were still somewhat brittle and liable to fail during cold shocks. Note also the comment that lamps should only be cleaned whilst alight - in which condition the filament exhibits a greater degree of elasticity and is less likely to suffer brittle fracture.
The filament in this lamp is supported by a transitional design, employing heavy nickel-iron wires at the cap end and fine spring-loaded molybdenum at the other. The first tungsten lamps employed heavy supports at both ends, until 1910-1911 when it was learned that it was advantageous to keep the filament under tension. Fine moly wires served this purpose and were intially applied at only one end in view of the difficulty that operators experienced in their handling, but were eventually adopted for both sets of supports once the fully automatic Hofmann machine had been developed. The platinum wires in the pinch-seal of the stem pre-date it to the use of Dumet, which was not introduced until 1913.