Glowing pickle demonstration

Applying line voltage across a pickled cucumber causes it to glow.

Sodium (or other) ions within the pickle emit light as a result of atomic electron transitions, although it is not clear why the luminescence occurs at one end of the pickle.

[1] The glowing pickle is used to demonstrate ionic conduction and atomic emission in chemistry classes,[2] and also as a demonstration in lighting classes.

[3] The first known fully documented demonstration was in a 1989 report from Digital Equipment Corporation.

[4] Although this was published as a full technical note and written up as a scientific paper, the publication date, April Fools' Day of that year, gives some indication as to the light-hearted nature of the document.