Episode 1 of 2

Carbonized Thread Filament Test

When: 22 October 1879
Where: Menlo Park, New Jersey (locality; exact site not stated in sources)
Part of: Edison's incandescent lamp: carbonized-thread test, patent application and first public demonstration

Edison's first successful incandescent lamp test occurred on 22 October 1879, with the filament burning for 13.5 hours.

After an earlier filament of cardboard carbonized with compressed lampblack burnt out too quickly, Edison achieved a first successful test on 22 October 1879. The lamp lasted 13.5 hours, demonstrating that a carbon filament could sustain light long enough to be practical, though the filament eventually failed and further refinement continued.

Sources

Incandescent light bulb Wikipedia, revision of 2026-09-23
Thomas Edison Wikipedia, revision of 2026-10-04

Machine-drafted from the cited Wikipedia passages and checked by a reviewing model, not by a human editor. Every passage cites the revision it was written from; dates and places follow those passages.