identify your lightbulb > bulb identification key


STEP 5: Filament Material and Configurati
on [Part I: Carbonized Cotton or Cardboard]

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 threadlike in appearance and charcoal black in color and is mounted in a hair-pin configuration. This is a carbonized cotton thread filament. This filament was the design that Edison used in his first successful electric lamp experiment in October of 1879 that was said to have burned for some 40 hours. [41ab]


OPTION B: Filament is threadlike in appearance, charcoal black in color and looped once or several times over in a spiral. This is a carbonized cotton thread filament. Looping the filament effectively increases the length of the filament without taking up more space inside the bulb. [41a]


OPTION C: Filament is vertically flat, carbon black in color and shaped like a small horseshoe with rectangular ends connected to the inner leads. This is carbonized Bristol cardboard filament. It was used in Edison’s first commercial lamps that he sold. They reportedly could burn for some 600 hours. [41aa]



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

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