"Edison's first simple 'wire in a bottle' was one of the first electrical devices." 

As a collector of insulators and related electrical items, I became fascinated with old glass light bulbs.

"Fundamentally, an incandescent lamp is a simple thing -- just a wire sealed in a glass bulb with a few supplementary parts, but it is very precisely made. Electric current passing through the filament wire heats it to incandescence, and light is produced. It is necessary to heat the filament to temperatures in the neighborhood of 5000 (degrees) F., yet the filament does not burn up because it is either in a vacuum or is surrounded by inert gases that do not combine chemically with the tungsten metal. A tungsten filament operates at a temperature higher than that of any heat source ordinarily encountered by man - a temperature at which asbestos or fire brick would melt like wax in a furnace -- and twice the temperature of molten steel. 

"The filament of a 6-watt 120-volt lamp is less than half a thousandth of an inch in diameter, visible only to the best of eyes. Side by side more than 2,000 fit in a one-inch space. Yet this wire is remarkably strong - in a 'cold' state, it is four times as strong as steel wire of the same diameter. 

"A filament which, in a single spot, is only one per cent smaller in diameter than specifications may reduce lamp life by 25 per cent. (In a 6-watt lamp, this would mean a difference in diameter of about five-millionths of an inch.) The reduction in life would be due to the more rapid evaporation of tungsten at the 'thin' spot. Some filaments are made by coiling tungsten wire around a mandrel which must be accurate to one ten-thousandth of an inch, or life may be affected as much as 20 per cent. Spacing between coils must be rigidly accurate, not only to avoid short-circuiting but also to avoid concentration of heat at one point. Inaccurate spacing may affect life by 10 per cent. Furthermore, a single drop of moisture distributed among 500,000 lamps will cause early blackening in all of them. 

"A 100-watt coiled-coil filament starts as a tungsten wire 0.00249 inches in diameter and 23 inches long. After the first coiling, the length is reduced to 3 7/8 inches. The coil, now consisting of 850 turns, is again coiled, leaving the finished filament only 11/16 inches in length. Because of the high concentration of heat with this coiled-coil filament, efficiency over the single-coiled filament of the same length is increased by 10 per cent...." 

There you have it, "everything you always wanted to know about a light bulb..." as told by the General Electric Company lamp division.

Replica of Edison's first operational lamp - 1880's

1903 cargon filament  light build

The very old carbon filament lamps are collectible and will make an addition to a collection. 

Several of even the oldest bulbs in my collection are still operational. They include a heavy glass bulb filled with bubbles and flaws, pointed top and various patent dates. The dates refer to a time period around the turn of the century. My insulator room is illuminated by an old porcelain street light complete with insulator and carbon filament lamp. The rest are supported by porcelain old sockets. 

To find them, look around junk shops, barns, old houses, etc. It is also amazing that such a fragile object such as a light bulb could have survived nearly 3/4 of a century and still be in working condition! It has been reported that a fire station in a central California town still has an antique carbon filament light bulb "burning", nearly 3/4 of a century! (Don't make them like they used to.) 

I must stop and ask myself - another "bright idea", collecting antique light bulbs?