[LargeFormat] Van Ripper didn,t know

[animal]

> ----- Original Message ----- 
> From: "animal" <s.jessurun95@chello.nl>
> To: <largeformat@f32.net>
> Sent: Saturday, February 28, 2004 12:26 AM
> Subject: [LargeFormat] Van Ripper didn,t know
> 
> 
> > Just to be sure i mailed the M.Briggs article to Mr. van
> Rippen.
> > He was unaware of the radioactivity of an aero ektar!.
> > Is there any more quantified info available that you know
> of on these
> > lenses?
> > The reason is that i,m allready exposed to cosmic
> radiation and would like
> > to establish some sort of dosage received.
> > Where would one go to have this tested?
> > best regards
> > simon jessurun
> > amsterdam
> >
> >
>   I suggest contacting someone at George Eastman House and
> also Rochester Institute of Technology. By memory, GEH had
> to dispose of a number of lenses in its collection because
> they were radioactive.
>   Some of the first rare-earth glasses contained some
> Thorium because it gave glass with advantageous properties.
> It is sometimes stated that the Thorium was an untentional
> impurity in Lanthanum glass, but it was a delibrate
> addition. I don't have the patent numbers for the Bureau of
> Standards glass although I have the patents somewhere. The
> formulas for several glasses are in the patent and show the
> use of Throrium to obtain high index, low dispersion glass.
> The patent is not in Kingslake, I'm not sure where I
> orginially found it.
> 
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
> 
> 
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You gave me those nonths ago !
i must be able to find them somewhere.
But there were no exact dosage numbers given not even aproximations.
simon jessurun