A sea of sparks: Seeing radioactivity

5 hours ago

Alpha particles from radioactive decay (like from americium, radium paint, or uranium ore) produce tiny flashes of light when striking zinc sulfide-coated screens.
Seeing these scintillations requires complete darkness and dark-adapted eyes (20 minutes optimal), using averted vision to enhance sensitivity.
A magnifying glass helps direct the faint light (thousands of photons per alpha particle) into the eye's pupil to resolve individual sparks.
Alpha sources must be within a few millimeters of the screen due to limited travel in air; the matte side of the screen must face the source.
The effect cannot be filmed and is best observed firsthand; pre-assembled spinthariscopes are available for easier viewing.

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