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07-09-2018, 03:57 PM   #1
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Help reversing thorium oxide on my lens.

Hi, I'm new here. I have a few vintage primes and wanted to know how do you reverse the yellow oxidation? I have been using tinfoil wrapped around my Super Takumar 55mm with the front element exposed to the sun. For a few weeks with no success. Does anyone here know of any better methods?

07-09-2018, 04:05 PM - 1 Like   #2
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Welcome to the forum.
You could try a UV light.
07-09-2018, 05:01 PM - 1 Like   #3
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Ikea LED lamps are said to work.

JANSJÖ LED work lamp - IKEA
07-09-2018, 05:10 PM   #4
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QuoteOriginally posted by Prince Harbinger Quote
Hi, I'm new here. I have a few vintage primes and wanted to know how do you reverse the yellow oxidation? I have been using tinfoil wrapped around my Super Takumar 55mm with the front element exposed to the sun. For a few weeks with no success. Does anyone here know of any better methods?
I just put mine out in the sun with nothing "wrapped around" it, just the table on the deck under it - and in a few weeks the yellow was gone.

At this time of year you do need to be careful - after I did this I was warned that too much heat can melt the glue holding the elements together

07-09-2018, 05:16 PM   #5
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Isn't it the rear element that is thoriated?
07-09-2018, 05:24 PM   #6
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QuoteOriginally posted by Not a Number Quote
Isn't it the rear element that is thoriated?
I'm not sure
Why should that make a difference?
Any place you put it, if light goes through one element, it will go through all of them.
07-09-2018, 05:35 PM   #7
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QuoteOriginally posted by MarkJerling Quote
Welcome to the forum.
You could try a UV light.
Thank you! When the sunsets I bring it inside and place it under a lamp. I have tried reptile UVB bulbs and Blacklight bulbs to no avail.
07-09-2018, 05:40 PM   #8
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QuoteOriginally posted by reh321 Quote
I just put mine out in the sun with nothing "wrapped around" it, just the table on the deck under it - and in a few weeks the yellow was gone.

At this time of year you do need to be careful - after I did this I was warned that too much heat can melt the glue holding the elements together
From what I was told that isn't a good idea because it can cause oil to leak on the aperture blades. Which produces slow/sticky blade response amongst other issues.

07-09-2018, 05:41 PM - 1 Like   #9
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I have had good success with a reptile/terrarium UV bulb, such as the Repti-Glo 5.0 and 10.0 series:

https://www.amazon.com/Exo-Terra-Repti-Glo-Fluorescent-Terrarium/dp/B00101JI...70_&dpSrc=srch

I 'de-yellowed' a Takumar lens in about 2 days of continuous exposure at a distance of 4 inches. The compact CFL bulb doesn't heat the lens.
07-09-2018, 05:47 PM   #10
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QuoteOriginally posted by Not a Number Quote
Isn't it the rear element that is thoriated?
You are correct. However the oxidation forms on all of the elements.
07-09-2018, 05:50 PM - 1 Like   #11
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QuoteOriginally posted by Prince Harbinger Quote
Hi, I'm new here. I have a few vintage primes and wanted to know how do you reverse the yellow oxidation? I have been using tinfoil wrapped around my Super Takumar 55mm with the front element exposed to the sun. For a few weeks with no success. Does anyone here know of any better methods?
Here are two posts on Instagram from AUG 17 showing my use of the Ikea lamp which works very well.

Also the rear element is the one that used thorium, so it’ll take you forever to shine light through the front element and the thorium fog will never be completely and evenly removed. Note in my photo the IKEA light is focusing directly on top of the rear element.

Hope this helps a little.

Ned

Ned Bunnell on Instagram: ?08.03.17 My big science project. I'm using the Ikea JANSJÖ LED work lamp (see comment below about UV) to see how it reduces the Thorium??

Ned Bunnell on Instagram: ?08.05.17 Update on using the Ikea JANSJÖ LED work lamp to see how it reduces the Thorium fogging on one of my Super Takumar 50mm f/1.4 (7??
07-09-2018, 05:53 PM   #12
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QuoteOriginally posted by c.a.m Quote
I have had good success with a reptile/terrarium UV bulb, such as the Repti-Glo 5.0 and 10.0 series:

https://www.amazon.com/Exo-Terra-Repti-Glo-Fluorescent-Terrarium/dp/B00101JI...70_&dpSrc=srch

I 'de-yellowed' a Takumar lens in about 2 days of continuous exposure at a distance of 4 inches. The compact CFL bulb doesn't heat the lens.
Interesting, the one I have been using is the Exo Terra Sun-Glo 120V 60Hz 100W. Thanks for the response. I'll look into getting one of those.
07-09-2018, 06:01 PM - 1 Like   #13
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QuoteOriginally posted by Ned Bunnell Quote
Here are two posts on Instagram from AUG 17 showing my use of the Ikea lamp which works very well.

Also the rear element is the one that used thorium, so it’ll take you forever to shine light through the front element and the thorium fog will never be completely and evenly removed. Note in my photo the IKEA light is focusing directly on top of the rear element.

Hope this helps a little.

Ned

Ned Bunnell on Instagram: ?08.03.17 My big science project. I'm using the Ikea JANSJÖ LED work lamp (see comment below about UV) to see how it reduces the Thorium??

Ned Bunnell on Instagram: ?08.05.17 Update on using the Ikea JANSJÖ LED work lamp to see how it reduces the Thorium fogging on one of my Super Takumar 50mm f/1.4 (7??
I forgot to include this link. Here’s the main reason you don’t want to subject the front element of a lovely Tak to heavy UV treatment or try to clean it...

Ned Bunnell on Instagram: ?08.07.17 As a final tip if you're considering buying a Super Takumar 50mm f/1.4 or most early Tak lenses...The Thorium coating was only??
07-09-2018, 06:08 PM   #14
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QuoteOriginally posted by Ned Bunnell Quote
Here are two posts on Instagram from AUG 17 showing my use of the Ikea lamp which works very well.

Also the rear element is the one that used thorium, so it’ll take you forever to shine light through the front element and the thorium fog will never be completely and evenly removed. Note in my photo the IKEA light is focusing directly on top of the rear element.

Hope this helps a little.

Ned

Ned Bunnell on Instagram: ?08.03.17 My big science project. I'm using the Ikea JANSJÖ LED work lamp (see comment below about UV) to see how it reduces the Thorium??

Ned Bunnell on Instagram: ?08.05.17 Update on using the Ikea JANSJÖ LED work lamp to see how it reduces the Thorium fogging on one of my Super Takumar 50mm f/1.4 (7??
I had no idea I was doing it wrong. All of this time from being misinformed by a article I read. I followed you on Instagram. You have a lot of wonderful photographs. Thanks for the clarification. Everyone here has been very helpful.

---------- Post added 07-09-18 at 06:15 PM ----------

QuoteOriginally posted by Ned Bunnell Quote
I forgot to include this link. Here’s the main reason you don’t want to subject the front element of a lovely Tak to heavy UV treatment or try to clean it...

Ned Bunnell on Instagram: ?08.07.17 As a final tip if you're considering buying a Super Takumar 50mm f/1.4 or most early Tak lenses...The Thorium coating was only??
Thank you. Would you mind if I sent you some photos of some of the ones that I have? Maybe you could tell me a little bit about them?
07-09-2018, 06:31 PM   #15
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QuoteOriginally posted by Ned Bunnell Quote
I forgot to include this link. Here’s the main reason you don’t want to subject the front element of a lovely Tak to heavy UV treatment or try to clean it...
I don't understand difference which end you send light from; doesn't it go entire distance in any case??
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