| THORIUM GLASS |
 Kodak Pony 135-C camera from the 1960s, with a thoriated Anaston 44 mm f/3.5 lens.  Kodak projector lens (Ektanar 2 in. f/1.6) containing a doublet, one of whose lenses is a rather radioactive thorium glass. At bottom is the radioactive lens separated from an Ektanar doublet. The brown dis- coloration is evident. Thorium oxide can be
added to glass to increase the refractive index--simultaneously making
the glass quite radioactive. I haven't found any high-quality
modern thorium optics, but several decades ago thorium glass was common
in camera lenses.
One of the most ubiquitous of the cameras with radioactive lenses is the Pony 135 marketed in the '50s and '60s by Kodak as a beginner's camera, and thankfully it's cheap: $5 is about the going rate at antique stores. There are many other older 35mm cameras with "hot" lenses as well; always be ready to whip out the Geiger counter for any cameras spotted at flea markets. The second photo above shows a lens with considerably higher thorium content, taken from a slide projector. The thoriated glass actually forms only half of a doublet; to recover it, the doublet must be split apart. The thorium glass in this lens has developed a typical brownish discoloration caused by radiation damage. |
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