US Army Amp Meter

This is a 1950s instrument, used for measuring the amount (in amperes) of electrical current in a circuit. It has a self-luminous greenish-yellow painted dial, which, if exposed to UV light, emits a brilliant glow in the dark. The paint, like all luminous paint of its kind produced at that time, contains dangerous levels of the highly radioactive chemical element, radium. However, handling this amp meter is safe as the paint is behind glass and cannot be ingested. 

Radium was discovered at the turn of the century by Marie and Pierre Curie, and was industrially produced and widely used for self-luminous paint from 1910. Ten years later its serious health effects were revealed to the world during a lawsuit filed by the ‘Radium Girls’, women who painted the dials. As the painters would ‘point’ their brushes using pursed lips, they absorbed high levels of radiation, leading to sores, anaemia, and bone-marrow and mouth cancers. It emerged that the company producers and scientists had known the dangers and protected themselves, but neglected its employees, even accusing them of having syphilis. Marie Curie herself eventually died of aplastic anemia from exposure to radiation. 

The dial on this meter no longer produces a strong light due to the breakdown of another substance in the paint, not the decay of radium which has a half-life of about 1600 years. This means that even very old objects containing radium will stay radioactive, and need to be stored carefully; even Marie Curie’s cookery book is kept in a lead-lined box. After the 1960s, radium paint was replaced with tritium, which, although dangerous if ingested, is far less radioactive.