Aero-Ektars: Does UV light remove the brown stain?

In a few threads it has been claimed that UV light will remove or bleach out the brown

radiation stain in the rear element in Aero-Ektar Lenses. Has anybody actually done

this? If so, what light source did they use and for how long?

 

Also, how big are the 12" Aero-Ektars? Can they be fit on a 6x6 lens board?

 

thanks in advance,

I've used UV Blacklight 18" lamps. Summicron lens at 2cm clearance

and mirrored below for 250 hours. The tubes were recommended by M. Briggs and I've graphed the relative results obtained vs time.<div></div>

After reading the posts on this subject I tried it on my only "radioactive lens," a SMC Takumar 50mm. One of the elements had turned rather brown/yellow, enough so you felt like you had a filter on it when looking through the viewfinder. I got a compact UV tube ($9, looks like a typical compact florescent bulb) and put it in a polished reflector at close range, since the tube puts out very little heat. I put foil around it to concentrate the light on the glass. Every couple days I'd flip the lens over so the light went in both ends over time. The improvement is subtle at first because it takes so long (3 weeks or so, and of course at first you want to check it right away to see if it works...) but when I was done the change was a 95% improvement, maybe more. At least for me, on the lens I used, it worked quite well. I was extremely doubtful this would work, but the lens is a great one for 35mm and the UV lamp was only $9 so I figured why not try it. Others have recommended a tube-style lamp from Wal-Mart, but that isn't what I used. What I used is sold in electronics stores as a black light "party" lamp, which screws into a normal round socket.

OK, OK, maybe it was only 80% improvement.

<p>Yes, the people who are reporting that UV light will bleach the brown discoloration of thorium glass are correct. In the thread <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=0054IM">yellowish cast looking through 35mmf1.4</a> I describe how I treated a 35 mm f1.4 Nikkor lens. I have since treated a 12 inch f2.5 Aero-Ektar. In the Aero-Ektar the brown color was greatly reduced but not elminated after one month of exposure, 24 hours a day, to light from a BLB blacklight fluorescent bulb.</p>

 

<p>To use the technical terminology of optics, the f2.5 Aero-Ektars from WWII have two radioactive elements in the rear cell. The rear cell contains two groups, with the two inner elements being made of thorium glass. This is described on my <a href="http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html">Aero-Ektar webpage</a>. Kelly Flanigan posted the cross-section diagram from the patent on <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=004cye">another thread in this forum</a>. Elements V and VI are the ones made of the thorium glass.</p>

 

<p>The rear cell of a 12 inch f2.5 Aero-Ektar is about 5.5 inches in diameter, so it might fit onto a 6x6 lens board. The real problem is that the lens is HEAVY. I just weighed one without the lens caps -- 11 pounds 12 ounces! (or 5.3 kg) Few if any LF cameras intended for "normal" photography will have front standards that can support this much weight. If you attached the lens directly to a 6x6 lensboard, the lensboard would have to be strong, such as fairly thick metal, or the 1/4 borders would break. One way to use such a lens would be to support the lens on a second tripod in front of the camera and attach a lensboard to the back of the lens via some very short bellows. The camera would need back focusing.</p>

For Michael: thanks much for posting the web page about the Aero-Ektars. It sheds much light on those lenses and also on some lenses that Canon made (at least one Canon lens, the early version of the FD 35mm f/2.0 is known to be radioactive and always suffers from browning of the glass.) Another question: roughly how much lead would be needed to provide effective shielding of the gamma rays from the Thorium daughter products? I'm not sure I have enough separation available to be comfortable around these lenses, but I do have access to lots of lead...

The 178mm F2.5 Aero Ektar lens is as radioactive as the old (approx pre 1980's) Coleman lantern mantles; before they are installed

Thanks very much for all the advice. I have been using the predicessor to the Aero-

Ektar, a 13.5" f/3.5 Eastman Anastigmat (only about 10lbs), in an old 8x10 ANSCO

studio camera with 9x9 lensboards, and was wondering if the 12" Aero-

Ektar would work. I will

try to 'bleach' a 7" Aero-

Ektar and see what happens.

Here's a link of minor interest, esp. for those of us who, like me, haven't actually had hands on an Aero-Ektar:<BR><A HREF="http://www.nwmangum.com/Kodak/K24-1.html">http://www.nwmangum.com/Kodak/K24-1.html</A>

Um, Jason, about alternatives to the 12" Aero Ektar. If your camera has a focal plane shutter (= Speed Graphic), you might look for a 12"/4 Taylor Hobson Telephoto as was fitted to Vinten F95 and Agiflite cameras. Nice sharp lens, covers 4x5, VERY short back focus (~ 85 mm, rear of rear element to film at infinity), not too heavy (around 3 pounds, IIRC). I doubt it can be put in shutter, but you can always use a Speed Graphic as a front shutter if it comes to that.

 

The late Steve Grimes put one on a 2x3 Pacemaker board for me, the adapter is a stepped ring; one end screws into the lens, the other end goes through the board and is held by a retaining ring. The lens could easily be put on a 4" x 4" board with an externally threaded flange.

 

Cheers,

 

Dan

Dan, thanks for the suggestion, but If I replace my current set up, the replacement

has to covers 8x10, and be faster than my current f/3.5. Shutters are irrelevant, since

my exposure range is between 5 seconds to 15 minutes.

Here I have three 178mm F2.5 Aero Ektars; one has a mount for a 4x5 speed graphic; another has a custom focusing mount that fits a 35mm slr; in the Exakta/Topcon mount; yet another is a junker; and has been taken apart. The Junker was obtained from ebay for about nothing; and was filled with aluminum turnings. Some person bored a hole thru the side of the lens! This lens was taking apart; and the rear radioactive elements are placed outside in the sun ; to bleach hopefully the lens clearer. At work we have a printer with a 5000W Uv bulb; I might build a tray inside to place the elements; if there is a place available; to catch some stray rays. The Uv is bad for the eyes; so watch out for this other danger; when playing with radioactive lenses.