GE Incandescent Tuff-Skin Rough-Service 150W
This lamp is designed for use in severe environments thanks to two specific design features - a shatterproof bulb coating, and a more robust filament construction.

The external bulb surface has been spray-coated with a silicone rubber coating, a technique first introduced by GE in 1968 based on the silicone materials invented by that company. It protects the bulb from breakage in case it should come into contact with hot or cold objects - for instance water droplets falling on a lighted bulb, or the spatter from welding. Mechanical impacts can still break the glass, but in that eventuality the strongly adhering coating conveniently holds the glass fragments together. The lamp is made in clear glass, but the textured surface of the coating provides an effective light diffusion with about 10% decrease in lumens. One drawback of the silicone is that it degrades when the lamp is burned cap down or above 150°F ambient temperature. A decade later the coating was changed to DuPont's Teflon, which is more thermally stable.

The filament construction is of a special design, first introduced by GE in 1928. The single coil has an unusually low mandrel ratio which increases its length such that it can be supported at more points than usual. This improves impact resistance but causes a significant drop in efficacy due to greater thermal losses to the gas filing and via the support wires. It is shaped into a two-tier castellated wreath so as to fit through the narrow bulb neck (see X-Ray image). Vibration resistance is improved by connecting the glass filament-support arbor to the stem press via a steel spud wire, whose elasticity helps dampen oscillating forces that may otherwise be transmitted from lamp base to filament.
Manufacturer: General Electric USA
Lamp Power: 150 Watts
Lamp Voltage: 115-125 Volts
Lamp Current: 1.25 Amperes
Cap Type: E26s/25 Brass & vitrite
Bulb Type: A-80 A-25 in eighths/inch
Bulb Finish: Silicone Rubber Soda-lime glass
Filament Type: C-17 Single Coil Castellated
Atmosphere: Argon-Nitrogen Red phosphorus getter
Luminous Flux: 1720 Lumens
Luminous Efficacy: 11.5 Lumens per Watt
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2700 Kelvin CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.460 CCy: 0.411
Rated Lifetime: 1000 hours
Burning Position: Base Up (to preserve coating)
Overall Length: 176 mm 615/16 inches
Light Centre Length: 132 mm 53/16 inches
Factory: Ohio Lamp Plant, Warren U.S.A.
Date of Manufacture: 1979 February Date Code: 86 (stem)
Original Value: Unknown
 
References: 1) GE Lamp Catalogue, 1979 USA.
2) GE Press Release, Tuff-Skin Lamps, October 23rd 1968.
3) GE Press Release, Tuff-Skin Lamps, October 23rd 1968.
4) A Century of Light, James A. Cox, publ. The Benjamin Company, 1979, p.217 (invention of Tuff-Skin Coating).
5) Lamps for a Brighter America, Paul W. Keating, publ. McGraw-Hill, 1954, p.152 (invention of Rough Service filament).
6) Photoelectric measurement of intact lamp, and of a second broken lamp to determine optical transmission of the coating.
7) Infrared Spectroscopy of a small piece of coating, which revealed the classic absorption peaks of Polydimethylsiloxane at 1412 and 1445 cm-1.
8) Combustion of a small piece of coating, which produced the classic white smoke of a silicone material due to formation of silica.
9) Energy-Dispersive X-Ray Spectroscopy of a small piece of coating, which identified its silicon-carbon-oxygen composition.
10) X-Ray scan of lamp to reveal the internal construction, and date code marking on the stem press.