||During the late 1880s an early 90s, Edison lamps underwent numerous improvements and design changes, with a new version being introduced practically every year. The situation stabilised somewhat following the introduction of the so-called "New Type Edison Lamp" featured on this page, which remained in production during the period 1893-1900.
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.
The platinum sealing wires originally penetrated the entire stem press. In 1889/90 the length of platinum was reduced to a minimum of 1/8" by welding to copper wires, the welds also being embedded in the press seal. This necessitated extra work in forming the delicate welds, a process which was superdeded in 1892-94 by the construction featured here. The inner copper wire was omitted, with the platinum section being connected directly to the filament.
The method of connecting the platinum leadwires to the filament is with a carbon paste, as introduced in 1886 to supersede the former copper plated joints. The base is of a type introduced in 1888 in which the number of threads was increased, refined in 1893 to the shape shown here. It was superseded only in 1890 when a more durable porcelain insulator replaced the Plaster of Paris employed in this lamp. The bulb envelope has been blown into a mould rather than in free air, a technique first introduced in 1892.