Prior to 1893 all Edison lamps employed filaments made from carbonised bamboo, a notoriously difficult material that introduced large variations in performance owing to the irregularity of this natural fibre. In 1893 the Edison factories adopted the squirted cellulose filament, a man-made carbon fibre of tremendously improved strength and uniformity.
Carbon filaments have a negative temperature coefficient of resistance—as they get hotter, their electrical resistance decreases. This made the lamp sensitive to fluctuations in the power supply, since a small increase of voltage would cause the filament to heat up, reducing its resistance and causing it to draw even more power and heat even further.
Even though carbon filament lamps were replaced by more efficent light sources, they have made a come-back for decrotive lightng over recent years.
Lovely old Royal Ediswan 'Carbon Filament' lamp rated at 230v- 200w. New condition in the original box, but I am not sure of the year of manufacture.
Lovley lamp, which looks to be quite old, due to the packing and output stated in 'candle power' rather than watts.
This lamp looks to be well used, but still works. Was recovered from Frenchey Hospital, near Bristol, just before it closed; fitted with a B22 Base.
This very old carbn filament lamp was bought by myself over 40 years ago, the lettering on packaging has faded, but I recolect that it is 240v 8 Candle Power. I have not illuminated this and have no intention of doing so.