Repro-Claron->Radioactive?

[Dave_B]

In a number of threads here and elsewhere it has been discussed that the Repro-Clarons are radioactive with some of their elements (the outer ones) having been made with Thorium doped glass. One post suggests that late model versions are not radioactive because Schneider stopped using this glass in the early 70's. Does anyone know if this is true and if so, what serial numbers correspond to when they stopped?
Thanks,
Dave B.

[Kevin Crisp]

I've seen a number of these, including serial numbers into a range past the early 1970's. All of them had moderately tea brown glass when I bought them, and about 3 weeks of close exposure to a UV lamp cleared that up. I can't rule out the possibility of this rumor being true, but then I don't know when these lenses were discontinued. The worst lens I've had, by far, for the browning effect, was a SMC Takumar 50mm f:1.4 lens.

[Dave_B]

Kevin:
Thank you for the information. It was helpful.
Cheers,
Dave B.

[Kevin Crisp]

I just checked my 3 current Repro-Clarons. Dates of manufacture per the serial numbers on Schneider's site are 1970, 1971 and late 1976. All had the brown glass issue. I have no idea if these were made later than serial number 13,000,XXX.

[Phil]

Kevin,

What did you use for a UV lamp to clear the Repro-Clarons?

Phil

[Gene McCluney]

One should be able to use direct sunlight to clear. Put the lens on your patio in direct sunlight.

[Joseph O'Neil]

Very easy way to test for a radioactive lens. Only costs you a single sheet of film.

Take you lens into your darkroom. If you have no darkroom, use a changing bag or tent. If none of the above, make temporary darkroom - like a closet at night. In you darkoom, take out a single sheet of B&W film. I used HP5, 4x5 for my test. Faster ASA / ISO seems to work a bit better.

Leave the lens, in the dark, or in the changing bag overnight , but better for 24 hours, on top of the sheet of film. If you notice brown or brownish or browner elements on one side of your lens, but that side directly down touching the film.

Next day develop that sheet of film as you would a if you exposed it on a regular basis. A "hot" lens will show all sort sof little streaks, comet like little asterix marks, etc. Kinda cool actually. You'll know it when you see it. It's the radiation fromt eh lens striking the emulsion that does it.

I did this with my Aero - Ektar lens, and it was kinda cool. Today I had a rad detector for such things, but this is an easy way to find out for sure. The only thing I cannot tell you is how "hot' the lens is, but I would assuming sitting down and watching a movie with the lens on your lap is maybe not a good idea. :)

joe

[Arne Croell]

I just checked my 3 current Repro-Clarons. Dates of manufacture per the serial numbers on Schneider's site are 1970, 1971 and late 1976. All had the brown glass issue. I have no idea if these were made later than serial number 13,000,XXX.

I have a 305mm/12" Repro-Claron with serial no. 13504xxx, that is a production date between 1978 and 1979. That lens is not radioactive (I have access to a Geiger counter).
So together with Kevin's information, the switch was between 1976 and 1978/79, somewhat later than for other lenses like the Apo-Lanthars or Schneiders own Xenotars where the glasses were changed in the early 1970's.
Not exactly sure when Schneider dropped the Repro-Claron in favor of the similar Apo-Artar; they acquired Goerz in 1972 I think so there was apparently some coexistence for a while.

[Kevin Crisp]

The bulb I used looks like a compact florescent bulb except the tube is violet. It is made by Feit Electric, it is 15 watts, the model number is BPESL15T. I bought it off the shelf at Frye's and have seen them there many times. It puts out only a little heat, so I put the lens elements about 3" from the tube, on shiny aluminum foil, and leave it like that for a week at a time. Every now and then I turn the elements over to do both sides. You will see improvement in a week. The benefits seems to max out at about 3 weeks. At that point the single cells will look clear when held up to a white background, a pair of cells will have a very slight tea color to them.

[Dan Fromm]

One should be able to use direct sunlight to clear. Put the lens on your patio in direct sunlight.Um, Gene, where I live all sorts of crud falls out of the sky. Rain, snow, bird shit, soot, pine pollen in season, ... So I set my browned lenses, including a 55/8 ReproClaron that I've since sold, to bask under a UV lamp in the garage. For some things a controlled environment really is better.

[Kevin Crisp]

And indoors you can admire the way the glass glows yellow when you give them the UV treatment.

[Dan Fromm]

Um, Kevin, my TTH tessar type process lenses and little Repro Claron didn't fluoresce when irradiated. They just cleared, slowly.

[Kevin Crisp]

I think the ones that glow yellow under the UV have better bokeh. Sorry.

[Phil]

Thanks, Kevin. I'm anxious to see if my 19" glows.

[Kevin Crisp]

I was kidding, of course.