Thorium Glass in Xenotars and Planars?

I've been searching the web and I see occasional mention that some 135 Xenotars

used Thorium glass in the rear cell.

 

Is there any way of telling by serial number, etc whether my Xenotar is one of them.

 

I'm asking mostly to see if I need to take any extra care in storing the lens

and to avoid possible film fogging (I tend to leave a loaded grafmatic on the

camera I use the Xenotar on)

 

Also, Did 135 Planars ever use Thorium glass?

I have not noticed any yellowing in the lense, btw.

Dunno. I do have a radioactive Kodak aerial lens. If it fogged film, would they use it? Just use

your film in a timely manner and worry not. Oh, and I wouldn't sleep with under my pillow

for years. Otherwise, worry not. If it ain't yellow, the same thing - don't worry.

If a google advanced search for radioactive lens does not give you a definite answer then test the lens.<br>Place said lens with lens cap removed on a sheet of Polaroid B&W sheet film, or in a darkroom or changing bag use a sheet of film, emulison to to glass of lens, or piece of conventional photo paper and allow to sit undisturbed for 24~48 hours then process the film or paper as normal. Any hint of a ring or exposure under the glass area means it is "HOT. If hot it will not fog film unless film and lens are left on the camera for several hours for narrow body cameras to days for thick body cameras. <br> Other precautions were stated in above post.

I tested an Aero-Ektar in a manner similar to Charles' suggestion. I used 400 speed film inside of a 4x5 film holder, with the lens and holder in contact, and something like a week or more of exposure. With this setup, the density from a one day exposure would probably be pretty weak. This tells you something about the risk to your film when used in a camera -- perhaps a problem if you leave the lens and film close together for a day or more.

 

If you can't see any "yellowing", as you say, probably it doesn't have the thorium glass. But the "yellowing" can be reduced by exposure to UV light, so this isn't conclusive. To me, the color is more amber, like that of tea. A good way to check for the color is to view white paper through the lens.

I have three Nikkor 35mm 1.4 that have the hot glass, and I have a Zeiss Planar 80mm 2.8

that covers 6x9 and it has the same yellowing of glass. I think its possible to have a

Xenotar or another Planar that could be hot.

Funny, my 80/2.8 Planar is crystal clear and doesn't cover 6x9.

I have a 135 mm Xenotar with serial number 5,968,xxx that has thorium glass. It measures radioative with a Geiger counter and has a pale amber color. Same for a 105 mm with serial 4,881,xxx.

 

Maybe people who have a non-radioactive Xenotars, proven by measurement with a Geiger counter or other radiation detector, could report serial numbers, and we could bracket the transition.

 

For some reason Schneider redesigned the Xenotar to not use Thorium glass fairly early, but as far as I know, the Repro-Claron always used Thorium glass.

In 35mm Vistavision there is a 150mm F2.8 Xenotar thats non radioactive.

Folks knew the Kodak Aero Ektars were radioactive even in the 1950's and 1960's. I'm not sure what all the recent concerns are all about. The wisdom of 1/2 century ago is that one didnt use radioactive lenses for eyepieces; medivcal probes, or sleep with them in your bed. The 113 mm Kodak Ektar I have thats made in the early 1970's is radioactive; as our my 3 Kodak 178mm Aero Ektars, . In sweep of the house I found more radicactive items in the Kitchen and pantry than photo stuff. You can have radicactive glazes in pottery; or a radicactive glass trinket in the kitchen window. Old 1970's spare unused Coleman lantern mantles here are radiactive; plus the better grade 1960's/1970's Fluke differntial voltmeter neon NE-2 variant spares that are used in the feednack circuit. Doping the neon lowers the firing voltage. <BR><BR>Folks fears over life's risks needs to be less irrational (good versus bad) and more of a long analog scale.

There can be radioactivity or chemical wastes in that free soil your buddy got you. There can be radioactivity in your rock collection, Jewelry, Watches. Your antique pottery collection might emit more than hundreds of camera lenses that you just sold off as dangerous. Then there are smoke detectors, fireplace bricks,<BR><BR>The average Joe would be safer with smoke detectors, moderate sunshine instead of frying, less fat intake, more exercise. The concept that the sunburn they just got while mowing the yard being more harmfull than the Aerial lens in the garage cannot be fathomed my most. The concept their grandmoms broken pottery collection being harmfull cannot be fathomed either. The uranium glazing one ones hands while pieceing them together probably is not to great to get in ones lungs.<BR><BR>There are houses with radon gass seeping up thru the ground so its like smoking a pack of cigs a day. <BR><BR>The roads are radioactive in a couple of USA cities.