Fogplate

Fogplate, a grizzled lamp-lit chemist, holds a green lamp over an open wooden case.

The Physics

Henri Becquerel suspected that uranium salts, made to glow by sunlight, might give off X-rays. Paris stayed cloudy in late February 1896, so he put plates wrapped in black paper, with uranium salt on top, in a drawer. On 1 March he developed them anyway and found strong images: the uranium emitted penetrating rays with no sunlight at all (Comptes rendus 122, 501, 1896). It was radioactivity.

uranium → rays, no light needed

• uranium salt: potassium uranyl sulfate in his first tests
• plate: photographic plate wrapped in black paper

Marie and Pierre Curie took up the work, named radioactivity and found polonium and radium. All three shared the 1903 Nobel Prize.

Honest caveat: Becquerel at first thought the rays were a kind of long-lasting phosphorescence; their nuclear origin came later.

On the sticker

Fogplate holds a glowing green lamp and opens a wooden case of plates. Printed text: FOGPLATE with the line 1 MARCH 1896. Pixel-art kiss-cut vinyl sticker, white, in 2″, 3″, 4″ and 6″ sizes.