[chrisser]

It used to be used in those Coleman lantern glass mantles.

I've always heard those were slightly radioactive. One of these days I'm going to get myself a Geiger counter.

I've often wondered why. Is the material they're made out of inherently radioactive or is the thorium added for some particular property it gives?

[JoeFromSidney]

Thorium oxide glows when heated. Gives off a nice white light. Back in high school I used to expose photographic film to those mantels, then develop the film to show the weave of the fabric in the mantels. O Very neat.

[JoeFromSidney]

You don't need a Geiger counter. Back in high school I used to place gas mantles next to photographic film, then develop the film to show the fabric pattern of the mantles.