Abstract: An electrodeless fluorescent lamp having a lamp envelope with an inner phosphor coating and containing a fill capable of sustaining a discharge when suitably excited by an electric field includes an electrically conductive coating on the exterior of the lamp envelope. The electrically conductive coating is also light transmissive and is effective for confining the electric field to within the lamp envelope.

Abstract: Electric discharge lamps of extended life can be produced or cheaper materials used in their manufacture by providing on the internal surface of the envelope and on the exposed surfaces of internal components a protective coating of a metal phosphate or arsenate glass. External surfaces can also be protected against corrosion in air or in the atmosphere within an outer jacket, where this is employed. The coating may be applied in a liquid medium which, preferably after draining, is warmed to evaporate the medium and thereafter baked to form the vitreous coating.