Vitrite is a very lowfusing point blackglass mainly used for theinsulation base ofelectric lamps. It used to be made by the Vitrite Company.[1] Vitrite can be calledfoam glass because the mineral from which it is obtained is a spongy mass varying in colour from white to black depending on impurities.[2]
To make the electric lamp, molten vitrite is poured into the shell up to a height of approximately a quarter inch (6 millimeters). A plunger is brought down to force the plastic glass into shape and fix the contacts.
Vitrite is referred to as glass but in fact it is anenamel which contains a high proportion oflead (II) oxide to give fluidity, and considerable quantities ofmanganese oxide to produce a black colour.