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View Full Version : Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts



renditiont
4-Aug-2017, 03:25
I am just wonder if anyone here was able to completely cleared the yellowing of the Bell and Howell 6 inches f/2.5 or AE 6 inches f/2.5 ?
I have no problem clearing out AE 7 inches' yellow in 1 day, but I am still trying to wrap up the remaining yellowing of B&H 6''.

Basically I found out this lens have both thorium on both front and the back groups, unlike the AE7 which has only in the rear group.
For tool , I used an LED 300 Watts grow light that I already have several years, which has full-spectrum and more UV than regular Ikea LED light .
It is also convenience because I can mass bleaching several thorium lenses at the same time. I surmise that the bleaching will speed up much with higher wattage , say 600 watts or 1200 watts

With this particular lens I was able to clear most of the yellowing within 2 days (12 hours per day) , about 90%, but it seems the last 10% is hard to get rid of.
FYI I am still using the LED light to clear off the remaining as mentioned above.

I post some pictures for your consideration, and a video as well (that has flickering which showed the pulsating emission) .



B&H Before Bleaching

https://c1.staticflickr.com/5/4368/36197218262_896e46607c_b.jpg

https://c1.staticflickr.com/5/4399/36365775165_e0153cb1c4_b.jpg

B&H After 2 Days of Bleaching

https://c1.staticflickr.com/5/4339/35968960040_8cc677b348_b.jpg

https://c1.staticflickr.com/5/4349/36321320056_175923281e_b.jpg



Flickering video of the bleaching currently


https://www.youtube.com/watch?v=TJahfUKjXgw

Mark Sampson
4-Aug-2017, 08:20
Trippy video, man! Seriously, it seems like you're on the right path. I'd just keep on; there's no exact prescription for the treatment you're trying.

EdSawyer
4-Aug-2017, 09:06
I'd say continue also. I have 2 or 3 of these, and have partially bleached one but haven't gotten to the others. I did fully disassemble them (8 elements I believe), so maybe doing so would help more too.

Have you shot with them at all? I haven't gotten around to shooting with mine but hopefully will someday.

-Ed

renditiont
4-Aug-2017, 13:28
I am putting another 12 hours and the yellow is still there. It is driving me crazy. I will probably put up with it for another 12 hours.
I think it is starting to follow this curve

https://c1.staticflickr.com/5/4433/36197218172_38dd225c31_z.jpg

Pfsor
4-Aug-2017, 13:42
I am putting another 12 hours and the yellow is still there. It is driving me crazy. I will probably put up with it for another 12 hours.
I think it is starting to follow this curve

https://c1.staticflickr.com/5/4433/36197218172_38dd225c31_z.jpg

Hmm. How did you measure the bleaching percentage?

Chauncey Walden
4-Aug-2017, 13:59
Just think of it as saving you the cost of a K2 filter for B&W.

renditiont
4-Aug-2017, 14:09
Hmm. How did you measure the bleaching percentage? no i am just eyeballin' the percentage ;) the yellow is not that visible if I look through the lens, but if I put it against a white paper it is still there.

renditiont
4-Aug-2017, 14:11
Just think of it as saving you the cost of a K2 filter for B&W.
I definitely do not want to pursue this bleaching for long. Probably another 12 hours before I give up :D.

Corran
4-Aug-2017, 14:32
I have one of these that for a year was at a local machinist while he tried to figure out a good way of attaching it to a Pacemaker board. He never got around to it. I took it home and put it facing in to a UV light, where it sat for months. It never fully cleared, but it got better. My guess is that it won't clear fully.

renditiont
4-Aug-2017, 15:01
I have one of these that for a year was at a local machinist while he tried to figure out a good way of attaching it to a Pacemaker board. He never got around to it. I took it home and put it facing in to a UV light, where it sat for months. It never fully cleared, but it got better. My guess is that it won't clear fully.

Thank you Corran for ...clearing... it up. Guess I will yank my light in a few minutes :D

Mark Sampson
4-Aug-2017, 15:13
Just had a thought... the external elements may be acting as a UV filter, reducing the effectiveness of the treatment. We're way off the map here, though. Perhaps the tint can be cleared up, perhaps not. Certainly the lens designers and optical glass scientists were not aware of this effect in 1944!

renditiont
4-Aug-2017, 15:28
Just had a thought... the external elements may be acting as a UV filter, reducing the effectiveness of the treatment. We're way off the map here, though. Perhaps the tint can be cleared up, perhaps not. Certainly the lens designers and optical glass scientists were not aware of this effect in 1944!

I disassembled the lens into 2 parts to accelerate the bleaching and let them face upside down as in the video because I believe the thorium/yellow parts are located there. Regardless, I gave up on completely clearing it up as well. I think those elements are physically tainted .

If anyone else was successfully in clearing it up please let me know. I have another user on facebook also gave up on clearing it.

LabRat
4-Aug-2017, 16:17
I had a Kodak AE that had a nice gold color that I left alone as it was a unique color warming filter, so if life gives you lemons...

Steve K

Dan Fromm
4-Aug-2017, 17:35
Hmm. OP, might you be too impatient?

I ask because I've used a BLB fluorescent tube to clear a few lenses with radiation damage. 55/8 Repro Claron, 6"/9 and 10.16"/9 TTH Copying lenses and 12"/9 Apotal. Clearing took months.

renditiont
4-Aug-2017, 17:51
Yeah I think I am impatient. But I am perfectly fine with a bit of yellow as well. I realized I am getting a diminished return with this 300 Watts Grow Light LED . Maybe if I have proper LED UV light with much less power consumption then I'll be motivated again.
Btw I used this light on a bunch of other radiation/yellow lenses (about 8, 2 not shown) and they cleared up within the first day or second day even with the 180 watts LED :D Guess the last man standing :mad:

https://c1.staticflickr.com/5/4365/35968897530_e088846dde_c.jpg