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How to Make a Simple Carbon Filament

Thomas Edison, by his own admission, tried at least six thousand different "vegetable growths" in his search to find a material suitable for a carbon filament. He settled on a particular type of bamboo, which he "carbonized" to create a filament. Carbon-filament bulbs were used for decades, even after more efficient tungsten filaments were introduced. You can duplicate some of Edison's process by making your own carbon filament.

Things You'll Need

"Stringy" organic material such as cotton string, bamboo fibers, corn stalk
Empty metal can
Box nail or awl
1/4"-grid hardware cloth
Tin snips
Six inches of heavy-gauge wire
Utility knife
Barbecue grill
Oven mitt

Instructions

- 1
  Remove the top from the can. With the nail or awl, poke a hole through the bottom of the can. You will be using the can upside down, with the open end on the bottom.
- 2
  Cut the hardware cloth to fit inside the metal can. Use the tin snips to shape it into a rough circle, about an inch larger in diameter than the can. Then snip a few darts into the sides of the circle so you can fold the edges to press-fit it into the can.
- 3
  Cut a couple lengths of the heavy-gauge wire and loop them through holes in the hardware cloth so they will hang below. Those will be the handles to slide the hardware-cloth shelf out of the can.
- 4
  Cut the raw material for the filament.
- 5
  Place the filament on the hardware cloth "shelf" and slide the shelf up into the can. The filament will be far more fragile when it is carbonized, so place it in the shape you would ultimately like it to be. Slide the shelf into the open bottom of the can, halfway or more toward the top.
- 6
  Start a fire in the barbecue grill. Let a good bed of coals develop.
- 7
  
  A fire of burning coals will heat the interior of the chamber, but the lack of oxygen keeps the filament from burning.
  
  Place the can, open-side down, into the middle of the bed of coals. Wear the oven mitt. Carbonization takes place when organic material is heated with little or no oxygen. By burying the edges of the can into the coals, you will limit the airflow into the can, and the oxygen will quickly be used up.
- 8
  Allow the fire to die out. Wearing the oven mitt, remove the can from the ashes and allow it to cool.
- 9
  Grab the hanging wires and carefully pull the hardware cloth shelf from within the can. If possible, have someone hold the can while you remove the shelf.

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