This bulb, which I estimate dates to the mid-1920s, marks the next-to-last

stage of light bulb technology after decades of innovation. When I look at it,

I see two important things.

First, there’s no tip. For 40 years, the tip created by sealing off the vacuum

tube was the norm. After 1920, the exhaust tube moved inside the stem.

Here, it’s attached to the top of the assembly with an evacuation hole that

opens to the inside of the bulb. Air was exhausted out the bottom, and the

tip was hidden in the base.

Second, this bulb features the last of the elaborate caged assemblies.

Thanks to an ensuing innovation, the long-wired tungsten filament could be

collapsed into tiny coils and the cage simplified, or eliminated altogether.

This significantly reduced manufacturing costs and increased lighting

efficiency.

The bold red background and filament are my homage to this bulb, made

on the cusp of the last major innovation before the light bulb’s design was

locked in for almost a century.