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12-13-2019, 08:30 AM - 5 Likes   #1
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Yellowed Thorium Glass Lens FIX- Cheap (under $20US), Fast EASY

I know there are other threads regarding using UV light to remove the yellow/amber/brownish tint which many 1950's-1970's Thorium glass containing lens develop. I'm adding this one because I found a super easy to use UV blacklight flood lamp which operates at a cool enough temperature to allow the lens to sit right on the flood light glass! I've done two fairly severely yellowed Takumar 50mm F1.4 lenses and the results have been OUTSTANDING.

Lens #1 was a late 1960's vintage Super-Takumar 50mm f1.4 with splotchy dark yellow elements. After about ten hours on the lamp face down and another ten face up, the lens is as clear as the day it left Japan. Lens #2 was a Super-Multi-Coated Takumar 50mm f1.4 from around 1971. It was evenly yellowed. I did the same treatment to it with equally excellent results. Photos of its treatment and the lamp are attached.

The BEST part? The UV flood lamp is only $16.99 US on AMAZON. It is a 10 Watt output version. They also sell 20 Watt and higher versions, however those lights generate more heat and would require the lens to be moved away from the lamp to keep the lubricant from overheating.

All you have to do is set the 10 Watt HouLight UV Black Light Flood Lamp on a flat surface with the light lens facing straight up. Plug the light into a 3 prong 110-115V receptacle. Take your Thorium yellowed lens, open the aperture fully and set it face down, centered over the LEDs in the UV lamp. I put mine on a rubber collapsable lens hood to be sure the lens elects didn't contact the lamp glass. After 8-10 hours, turn the lens over so the rear element is now toward the UV lamp and let it go another 8-10 hours. Check the lens by looking at something white under good lighting. If there is no more yellow cast (coatings are a bit yellow, so allow for that) you are DONE. If there is still some yellow, give it more time on the lamp. Easy. The HouLight is rated for 5000 hours of use, so you can do your friends lenses Too.

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12-13-2019, 09:19 AM   #2
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Thanks for the info. Ima gonna get me one of them things! Less hot is good.
12-13-2019, 09:27 AM - 4 Likes   #3
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Great find!

I'd also bet that this light would kill fungus and sterilize fungal spores, too.

And it might be fun for photography of rocks, fluorescent objects, etc.

The only caution is that too much UV isn't good for the eyes or skin so prolonged direct exposure close to the bulb should be avoided.
12-13-2019, 09:42 AM   #4
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I think I know what I'm ordering today.

QuoteOriginally posted by photoptimist Quote
I'd also bet that this light would kill fungus and sterilize fungal spores, too.
At 10W for a LED it woulnd't surprise me if it does. Maybe give all the lenses a good go as it wouldn't hurt.

QuoteOriginally posted by photoptimist Quote
The only caution is that too much UV isn't good for the eyes or skin so prolonged direct exposure close to the bulb should be avoided.
Might be fun to play with for illuminating things but unless you are big into raves I don't think there is a big concern for most people with this light and exposure. At 10W it also seems to fall into the category of don't look into laser with remaining eye.

12-13-2019, 09:57 AM   #5
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I think someone may have been rude to you. However, take it as constructive criticism and get other people to provide more feedback... Eventually you'll get there I would guess.
12-13-2019, 10:00 AM - 2 Likes   #6
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QuoteOriginally posted by UncleVanya Quote
I think someone may have been rude to you. However, take it as constructive criticism and get other people to provide more feedback... Eventually you'll get there I would guess.
Wrong thread, I suspect
12-13-2019, 10:05 AM   #7
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Scorpions glow under UV! This is cool and could be good for big fish tanks also.

---------- Post added 12-13-19 at 12:15 ----------

QuoteOriginally posted by MossyRocks Quote
Might be fun to play with for illuminating things but unless you are big into raves I don't think there is a big concern for most people with this light and exposure. At 10W it also seems to fall into the category of don't look into laser with remaining eye.
It is for about 100 square feet of area when used as a party light so I think as long as you don't stare at it for any length of time, you should be good.
12-13-2019, 10:18 AM - 1 Like   #8
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QuoteOriginally posted by bertwert Quote
Wrong thread, I suspect
Correct! Sorry I'm not sure what happened.

12-13-2019, 10:31 AM - 1 Like   #9
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QuoteOriginally posted by UncleVanya Quote
I think someone may have been rude to you. However, take it as constructive criticism and get other people to provide more feedback... Eventually you'll get there I would guess.
Huh??????? I hope this is a wrong thread post, otherwise I am extremely confused. Need a beer.
12-13-2019, 10:48 AM - 2 Likes   #10
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QuoteOriginally posted by steamloco76 Quote
Huh??????? I hope this is a wrong thread post, otherwise I am extremely confused. Need a beer.
Yes - as indicated above - completely the wrong thread. I posted on mobile - not sure how it got goofed up - likely user error.
12-13-2019, 10:59 AM - 2 Likes   #11
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purchased just now - hopefully I can get my Takumar 35/2 sorted and usable....
12-13-2019, 11:02 AM   #12
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Thanks for the info!
12-13-2019, 11:50 AM - 3 Likes   #13
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Wearing UV blocking sunglasses might be a prudent precaution if working around this light for any amount of time, though normally you would turn it on and walk away. Avoid cataracts later in life.
12-13-2019, 12:11 PM   #14
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QuoteOriginally posted by Apet-Sure Quote
Wearing UV blocking sunglasses might be a prudent precaution if working around this light for any amount of time, though normally you would turn it on and walk away. Avoid cataracts later in life.
My length of exposure was limited to the time it took to take photos with my Q7 and 01 lens. LCD screen, no reflex viewing. I set the UV light up in our guest room. Not even the dogs go in there.
12-13-2019, 01:36 PM - 1 Like   #15
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As long as the radioactivity is not impaired I am okay with using this method.

Looks good. Thanks for the report.
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