Electrodeless lamp with external insulative coating

An electrodeless, low pressure gas discharge lamp, comprising:

• (a) a vitreous envelope containing a discharge medium, said envelope being shaped with an external chamber for receiving an electrical excitation circuit and having a surface facing outwardly formed of adjoining, non-overlapping first and second sides;
• (b) said excitation circuit being effective for exciting said discharge medium to emit light with electromagnetic fields that are generated by said excitation circuit;
• (c) a circuit for supplying electrical power from power mains to said excitation circuit;
• (d) a housing for said circuit;
• (e) an electrically insulative skirt depending from said housing and aproximately encircling said first side of said envelope;
• (f) a transparent, electrically conductive coating atop said vitreous envelope that is ohmically connected to said circuit, and, through said circuit, is electrically connected substantially directly to one of said power mains at any given time;
• (g) a transparent, electrically insulative coating comprising a contigous, inorganic glass layer;
• said insulative coating being disposed atop said electrically conductive coating, extending fully over said second side of said envelope, and further extending over said first side, beneath said skirt, for a redetermined distance;
• and
• (h) said insulative coating having a minimum coating thickness of at least about 3.1 microns.