Swan Patents Partial Vacuum, Carbon Filament Incandescent Lamp

In 1850 he began working on a light bulb using carbonized paper filaments in an evacuated glass bulb.

By 1860 he was able to demonstrate a working device, and obtained a British patent covering a partial vacuum, carbon filament incandescent lamp. However, the lack of a good vacuum and an adequate electric source resulted in an inefficient bulb with a short lifetime.

Fifteen years later, in 1875, Swan returned to consider the problem of the light bulb with the aid of a better vacuum and a carbonised thread as a filament. The most significant feature of Swan's improved lamp was that there was little residual oxygen in the vacuum tube to ignite the filament, thus allowing the filament to glow almost white-hot without catching fire. However, his filament had low resistance, thus needing heavy copper wires to supply it.