Electric filament lamp, c 1905.
© Science Museum / Science & Society Picture Library
In a filament lamp the filament needs to be as hot as posible. Tungsten has the highest melting point of any metal, but is difficult to draw into a fine wire. From about 1905 some filament lamps such as the ones shown here were made with filaments of sintered tungsten powder and, although brittle, such lamps were used until drawn tungsten filaments became available about 1910.