The use of porcelain as an insulator [see A109] did not last very long.  The following year, in 1901, Bases with glass insulators were introduced in 1901 and have been in use ever since.  The base shown here has its entire copper threaded base molded over a black or blue glass insulator with one straight-sided or tapered copper contact terminal at the bottom of the base. The base is cemented to neck of bulb by waterproof cement between the bulb and base.  However, the use of waterproof cement was discontinued in 1933 with the advent of mechanically attached bases. [See A111]

NEXT PAGE in the Evolution of Lamp Bases

close window