[reh321]

Exactly. I had both ends up on a random basis, and it work fine either way. I had best results from the sun vs. a lamp. My S-M-C Takumar 50/1.4 Cleaned up nicely.

Exposure to the sun worked and left no visible damage to the lenses.
That is the important thing to me.
Now I need to remember to use them on occasion to keep them that way.

[stevebrot]

if a yellow stain is on the surface of the lens it is likely Thorim oxide Th0, Th02 or any other form of Th2,4+ and therefore removable.
both oxidation stages are yellow so it matches the description.

Once again. The color goes all the way through.

I doubt he will succeed with UV experiment and permanently remove the issue but I would try different approaches, it can't hurt. If the problem was a fungus of yellow color, UV bleaching on both lens surfaces will probably do the job. I always test for fungus first and dip my lenses in a light solution of hydrogen peroxide, works better than UV

If you are able to de-color a lens having radiation-induced color center activation with a surface treatment, more power to you. Your solution is unique.


Steve

[leekil]

if a yellow stain is on the surface of the lens it is likely Thorim oxide Th0, Th02 or any other form of Th2,4+ and therefore removable.
both oxidation stages are yellow so it matches the description.

Even if the color *didn't* go all the way through, wouldn't removing the top surface of a lens, even if it was a very thin layer, have an undesirable effect on the optical function of the lens?

[Prince Harbinger]

You guys are very knowledgeable and helpful. Here is two photos of my Takumar and two photos of my Mamiya that I just purchased.

Dropbox - 20180709_212612.jpg

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Dropbox - 20180710_192155.jpg

---------- Post added 07-10-18 at 04:53 PM ----------

Thank you, Steve, I assumed it is a thoriated glass only, without any coating but I was not sure since I never tried to remove the coating from an old takumar lens. This fact should make the removal even easier since there is no need to worry about the coating. Thorium is a not a reactor fuel it is slightly radioactive, probably below average continental runoff consisting of radon etc. there is nothing to worry about, one can test it with Geiger apparatus if concerns are an issue.

if a yellow stain is on the surface of the lens it is likely Thorim oxide Th0, Th02 or any other form of Th2,4+ and therefore removable.
both oxidation stages are yellow so it matches the description.


I doubt he will succeed with UV experiment and permanently remove the issue but I would try different approaches, it can't hurt. If the problem was a fungus of yellow color, UV bleaching on both lens surfaces will probably do the job. I always test for fungus first and dip my lenses in a light solution of hydrogen peroxide, works better than UV


I never managed to damage any lenses, I even ran spectrophotometry test to test for the changed composition of my washes, never found anything worthy of concern. I regularly use moderate solutions of ammonia vinegar ethanol and hydrogen peroxide to restore old lenses and I never managed to damage anything, even when i wanted to

I would be really interested in seeing your methods for cleaning. Do you have any videos on Youtube? Raw apple cider vinegar is the most acidic for natural solutions. It's good for killing mold. Not as good as using grapeseed oil, but I highly doubt you would want to dip your lens in it. Unless, you are dipping the element alone.

[Bob 256]

If you put your lens in the sun, you risk evaporating some of the lubricants in it (when the lens gets hot) which then condense on the lens elements (only a slight amount but that's too much).

Light which does the best job clearing the yellowing is deep into the UVA (350nm and lower if you have a source) and that wavelength is attenuated by the glass in the elements so it's best applied directly to the yellowed element. If you shine it in the other end, a good amount will be lost before it gets to the element that needs it. The suns output is fairly low at those wavelengths (thank goodness) so it isn't too effective so a better choice is a UV lamp or LED (some high output UV LEDs are available now). Use caution because those wavelengths will cause skin and eye damage.

[Prince Harbinger]

Update, I'm going to use this as my light source. It is the brightest lighting that I own. The only negative is it generates an extreme amount of heat. Photo below.

Dropbox - 20180707_140250.jpg

[stevebrot]

Update, I'm going to use this as my light source. It is the brightest lighting that I own. The only negative is it generates an extreme amount of heat. Photo below.

Dropbox - 20180707_140250.jpg

Do you have an IKEA near you? The JANSJÖ is just under $10 and is a well-established, low temperature, no damage your eyes way to clear yellowed radioactive lenses. As for your two lenses, it is tough to tell with a green background, but most Super Takumar 55mm f/1.8 have a radioactive element in the rear group. The Auto Mamiya/Sekor 55/1.4 is reputed to be radioactive as well. A yellowed lens is pretty obvious. The color is not so much yellow as a smoky yellowish brown.


Steve

[Prince Harbinger]

If you put your lens in the sun, you risk evaporating some of the lubricants in it (when the lens gets hot) which then condense on the lens elements (only a slight amount but that's too much).

Light which does the best job clearing the yellowing is deep into the UVA (350nm and lower if you have a source) and that wavelength is attenuated by the glass in the elements so it's best applied directly to the yellowed element. If you shine it in the other end, a good amount will be lost before it gets to the element that needs it. The suns output is fairly low at those wavelengths (thank goodness) so it isn't too effective so a better choice is a UV lamp or LED (some high output UV LEDs are available now). Use caution because those wavelengths will cause skin and eye damage.

Thanks for your response. Would the flashlight from my S8+ be suitable? I was thinking of putting it on top of the lens.
Since it doesn't generate enough heat to burn my finger to the touch. If not then what UV LEDs would you suggest?

---------- Post added 07-10-18 at 07:42 PM ----------

Do you have an IKEA near you? The JANSJÖ is just under $10 and is a well-established, low temperature, no damage your eyes way to clear yellowed radioactive lenses. As for your two lenses, it is tough to tell with a green background, but most Super Takumar 55mm f/1.8 have a radioactive element in the rear group. The Auto Mamiya/Sekor 55/1.4 is reputed to be radioactive as well. A yellowed lens is pretty obvious. The color is not so much yellow as a smoky yellowish brown.


Steve

Steve thanks for your time. I really appreciate it. I live in South Jersey, and have not heard of IKEA. I do notice that when outside the glass appears to be clear, but when I'm indoors it is yellow with a hint of purple. I have some pictures of my current setup that is likely overkill. It is making both lens warm, but I assume since they are wrapped in tinfoil they should be fine.

Dropbox - 20180710_222701.jpg

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[stevebrot]

I do notice that when outside the glass appears to be clear, but when I'm indoors it is yellow with a hint of purple.

I suspect what you are looking at is the reflection off the coatings. That is usually yellowish with some purplish and is quite normal. This thread is in regards to clearing discoloration that is evident when looking through the lens. The easiest way to visualize is to get a piece of bright white white paper and look through the lens (iris wide open) at about ten inches distance from your eye. Compare the appearance of the paper as viewed through the lens with that of the paper on either side. The paper should appear white. Ideally this should be done in natural light.

As for IKEA, the nearest store is probably in South Philly...

https://www.ikea.com/us/en/store/philadelphia


Steve

[Prince Harbinger]

I suspect what you are looking at is the reflection off the coatings. That is usually yellowish with some purplish and is quite normal. This thread is in regards to clearing discoloration that is evident when looking through the lens. The easiest way to visualize is to get a piece of bright white white paper and look through the lens (iris wide open) at about ten inches distance from your eye. Compare the appearance of the paper as viewed through the lens with that of the paper on either side. The paper should appear white. Ideally this should be done in natural light.

As for IKEA, the nearest store is probably in South Philly...

IKEA South Philadelphia Home Furnishings - IKEA


Steve

I'll try that test outside in the morning. I do notice the Takumar produces photos with a yellow cast. Unless it is normal for it to give off a warm color? I compared it to my Pentax 50mm 1.8 and that has a clear element with normal color.

[ddb]

Once again. The color goes all the way through.



If you are able to de-color a lens having radiation-induced color center activation with a surface treatment, more power to you. Your solution is unique.


Steve

Because the thread mentioned thorium oxide, I was under impression that color appears on the surface. There is no way thorium could come in contact with a sufficient amount of oxygen inside the glass. I apologize for the misunderstanding.

---------- Post added 07-11-18 at 12:24 AM ----------

Even if the color *didn't* go all the way through, wouldn't removing the top surface of a lens, even if it was a very thin layer, have an undesirable effect on the optical function of the lens?

I don't know. I never managed to hurt any deplorable lenses when testing the borderlines. Think of your teeth as an inferior porcelain or glass, how can something that doesn't hurt your teeth possibly ruins a high-end lens?

I've seen some cheap seventies window glass smoked by longtime exposure to HF vapors and sunlight, I worked in many labs worked with lab glassware. I compared my pre and post pixels. I tested my washes. Nada.


I am not saying it is impossible but it takes some serious effort to visibly corrode a piece of high-quality glass. This is the reason why glass is used in chem labs all over the world. I tried to remove a badly scratched coating using HF on a rokkor lens and I ended up trashing it.

[Not a Number]

It's not so much the glass to worry about but the coatings.

And tooth whiteners and acid erosion from eating acidic foods do damage tooth enamel. There are four generations of dentists in my family. I won't use tooth whiteners.

[stevebrot]

Because the thread mentioned thorium oxide, I was under impression that color appears on the surface.

The trace additive is thorium oxide, but in general usage the lenses are referred to as "thoriated" and the additive abbreviated to "thorium". Sorry for the confusion.


Steve

[leekil]

I've seen some cheap seventies window glass smoked by longtime exposure to HF vapors and sunlight, I worked in many labs worked with lab glassware. I compared my pre and post pixels. I tested my washes. Nada.


I am not saying it is impossible but it takes some serious effort to visibly corrode a piece of high-quality glass. This is the reason why glass is used in chem labs all over the world. I tried to remove a badly scratched coating using HF on a rokkor lens and I ended up trashing it.

Well, 70's windows and lab glassware isn't trying to be optically perfect, so that is kind of a different case. As you point out, it is hard to dissolve glass, but the coatings are the real issue as Not a Number mentioned.

[Bob 256]

Thanks for your response. Would the flashlight from my S8+ be suitable? I was thinking of putting it on top of the lens.
Since it doesn't generate enough heat to burn my finger to the touch. If not then what UV LEDs would you suggest?[COLOR="Silver"]

I'm not familiar with your flashlight - some are designed for UV output for examining minerals etc, but they are fairly weak. MPJA.com has some high output LED modules, one which into the bottom end of UVA (lower wavelength) and might do the trick though I'm not sure. You'd also need the constant current driver for that LED module which they carry as well. Again, be sure to use precautions with such a source - it's bright in the UV though it may not appear that bright otherwise, and you can get serious cornea damage from it as well as skin burns. Wear Yellow tint sunglasses when using it and avoid skin exposure.

Ozone or germicidal lamps are also available which go further into the UV spectrum but they are costly for a one time job which the LED might do for a lot less.

LED link: Ultraviolet LED, 10W, 365nM | MPJA.COM

and http://www.mpja.com/LED-Driver-10W-90-264VAC-Input/productinfo/32817+PShttp://

Ozone Lamp link: Standard Quartz Germicidal 254 nm UV Lamps | Light Sources

The color Thorium imparts is due to what are called "color centers" which develop in the glass itself throughout its thickness. It takes the high energy of UV light to reverse this process (bleach it). It's somewhat like the self-darkening sun glasses but in reverse. Ivory exhibits a similar phenomenon where it will yellow in the dark but whitens up when exposed to light.