A Newly Discovered Drawing of a Light Bulb by Thomas Edison, the Only One Fully Signed We Have Found Having Reached the Market, Never Before Offered for Sale

Our gratitude for the assistance of the Papers of Thomas Edison ~ Edison contracts with one of his hand-picked inventors to make improvements in the manufacture of incandescent lamps, and uses this drawing to illustrate his ideas

Albert Keller, who later played a role in manufacturing the phonograph and who invented the jukebox, was assigned to design “a machine whereby one man can form cups and 3000 inside parts in 10 hours, after two days trial of it.”

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Albert Keller was the assistant to Ezra Gilliland, Edison's best friend, and the two of them joined Edison at his New York and later lamp factory labs in 1885-1887. After Edison began to develop his wax-cylinder phonograph in 1887, Gilliland and Keller set up a factory to manufacture them with Keller as the superintendent. Gilliland became general agent for the phonograph. Keller was also a talented inventor, and created the first really successful and reliable coin-op phonograph (jukebox) in the United States, which he patented in 1891.

[caption id=""attachment_20534"" align=""aligncenter"" width=""1600""] Edison's drawing of his bulb, with the filament crossing it[/caption]

When Keller worked in the lamp factory labs, there was a pressing need to come up with a more efficient way to manufacture the inside parts in the bulb, particularly where the lead-in wires were attached to the filament. The small glass cup, which was attached to the vacuum pump that held phosphoric anhydride to absorb remaining moisture in the bulb, was also a focus of improvement. In 1886 Edison patented improvements in this process. The stem of the inside part of the bulb, which looks a bit like a cup and was hand made, may have been also referred to as a cup. Developing a machine for that would have been quite useful but, according to John Howell's history of the incandescent lamp, no machine for this purpose was developed until 1901.

Edison sought Keller’s assistance in improving lamp manufacture. Autograph letter signed with a lightbulb sketch, from the Edison lamp factory, September 30, 1886, to Keller, constituting an inventing contract. “I agree to give Keller $100 if he makes a machine whereby one man can form cups and 3000 inside parts in 10 hours, after two days trial of it. Machine to be furnished within two weeks.” Which of the two cups Edison had in mind here is not known for certain, but Edison’s technical notes may provide a clue as they discuss cups right at the time of this letter. Affixed to a thin backing.

On September 18, Edison wrote ""Made small cups on end of double barrel tube, ran two wires through them filled them with the following compounds and measured resistance.” Then on the 22nd, he listed mixtures of copper oxide and lampblack and a few other substances being experimented with. He kept improving techniques for manufacturing incandescent lamps, using hand-picked men like Keller, and continued to obtain patents for these improvements.

Our gratitude to the Papers of Thomas Edison at Rutgers and its scholarly staff for helping in our research. At the right of the letter Edison has drawn a picture of a light bulb. As to what he drew through the bulb, our research indicates it likely related to these experiments and a potential way of preventing what later became known as the Edison Effect and which caused blackening of bulbs.

This is one of only 2 such signed drawings to have reached the market, the other having sold decades ago and bearing only initials