I don't think there was radio active glass in any of these
There are some lists of radio active products, including lenses,
on the web.
Some kinds of barium crown glasses were discontinued. In
fact, I read that no one could make an original Tessar because
the glasses specified in the patent have not been available for
decades.
The patent for rare earth glass is RE 21175 G.W.Morey
assigned to Eastman Kodak Co. The original number was USP
2,150,694 The application date was 1936 and the issue date 1939
On 3/8/2020 12:35 PM, Uwe Wolfgang Steinke wrote:
I have a number of old SL66 lenses and I‘d like to keep Thorium out of my livingroom.
So - which lenses all had Thorium glas?
Am 08.03.2020 um 20:29 schrieb Ferdi Stutterheim (Redacted sender fwstutterheim for DMARC) <dmarc-noreply@xxxxxxxxxxxxx>:
I was wondering about the 4/55 mm Distagons of the Wide Angle Rolleiflex. When I was visiting the Rollei factory at the time the new Rolleiflex FW was manufactured, I was told that the original Distagon could not be made anymore because a certain type of glass was no longer available. They had to settle for the Schneider Super-Angulon 4/50. Could there be Thorium glass in the Distagon? Mine has not turned yellow (yet?).
Ferdi.
----
Ferdi Stutterheim,
Drachten, Netherlands.
Op 8 mrt. 2020, om 11:06 heeft `Richard Knoppow <dickburk@xxxxxxxxxxxxx <mailto:dickburk@xxxxxxxxxxxxx>> het volgende geschreven:
Thorium glass has properties that made it desirable for the very high performance lenses Kodak was making for defense purposes. They probably knew the glass would brown from the radiation but no one expected these lenses to have a service life of more than a couple of years.
