identify your lightbulb > bulb identification key

Filament Material and Configuration [Part II: Carbonized Bamboo, Squirted Cellulose, or Metallic Filaments]

Select the option most resembling your bulb from the drop-down menu to proceed to the next step. Please consult "option descriptions" for detailed info.

[The drop-down menu can be re-set by refreshing your browser window.]

FULL OPTION DESCRIPTIONS / IMAGE GLOSSARY: [Option titles are also linked to proceed to the next step.]

OPTION A: Filament is a long flat strip with flared or enlarged ends and has a shiny black appearance.  Cross section is NOT round but rectangular whose plane is parallel to our line of sight when bulb is held upright.  Filament, however, may be twisted throughout some of its total length.  May be mounted in a hair-pin configuration or looped once or several times over.   This is a carbonized split Japanese bamboo filament, which was in use from 1880 to about 1895. [42bf]

OPTION B: Filament is round in cross section but not thread like.  Filament is also quite long and black in color.  Could be mounted in either a hairpin fashion, two filaments in series, or single oval anchored loop of one filament.  This is a squirted cellulose filament, which was in use from 1893 to 1918 (when it was discontinued). [42scf]

OPTION C: Filament is round but not thread like.  Has a dull gray appearance and could be mounted in a hairpin fashion, two filaments in series, or single oval anchored loop of one filament in a straight-sided bulb.  This is a GEM (General Electric Metallized) filament invented by Dr. Willis Rodney Whitney [see A48] of the General Electric Company and was in use from 1905 to 1918. [42gem]

OPTION D: Filament has a metallic appearance and consists of either: one single long strand threaded over many horizontal supports (with end hooks) attached to the button rod (a long glass rod affixed to the stem tube and press); or numerous separate individual hairpin filaments connected in series about the same horizontal supports inside the bulb.  These are either tantalum or early tungsten lamps, which have very low electrical resistance so that the filaments or combination of filaments had to be very long and thin. [42mt]

OPTION E: Filament is short, single coiled about one inch long and metallic in appearance. (Note: see A43 to distinguish a single-coiled filament from a double-coiled filament.)  Coil is mounted horizontally in a semi-circular fashion on the two lead wires (bi-post mounting) and two or more wire supports attached to the shank, stem press, or button rod.  Or coil could be mounted vertically from one longer lead-in wire to the shorter lead-in wire [see A118].  These are coiled tungsten filaments. [42mc]

Feel Lost? Returning to Step 3 and re-starting the option process will often help you correct the misstep.

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