Archived posting to the Leica Users Group, 2001/07/27

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Subject: Re: [Leica] Radioactive glass in M lenses ?
From: David Prakel <>
Date: Fri, 27 Jul 2001 22:25:56 +0100

> Hugh Thompson writes:
>> Talking to a dealer this evening and he told me
>> that glass in some 1950's M lenses is radioactive,
>> and the lenses have added value because of their
>> rarity.

I thought the radioactive lens was the Thambar. Radioactive to the point
that it would fog a piece of paper if left standing on it for a fortnight.

Ruby colour cut glass for Eastern Europe is uranium doped for the colour and
a lot more radioactive than the Thorium glass mentioned here. Didn't the
thorium doped element go cloudy after many years?

Oddly enough my local area in England is famous for its Thorium poisoner who
work at a photo processing lab and put thorium in his co-workers tea.

David Prakel