Rehabbing a Black Lens?

[Richard Rumancik]

In the II-VI catalog there are detailed instructions for cleaning lenses that are mildly to badly soiled. There is a lot of other interesting technical info in the II-VI catalog concerning lenses and other optics. You can view it on-line here:

http://www.iiviinfrared.com/CO2-Lase..._products.html

The cleaning info starts on page 14.

[Gary Hair]

Maybe I missed it, but on what page did they mention oven cleaner?

[Richard Rumancik]

You are asking me Gary? You won't find anything about using lye in the II-VI catalog. I would highly doubt any lens manufacturer would recommend using lye to clean a lens.

[Gary Hair]

Nope, that was a rhetorical question.

[Kev Williams]

Why would any lens manufacturer recommend ANYTHING to re-hab a lens? They will always recommend a NEW lens, it's how they make money...

And in case anyone cares, I just test-cleaned a cracked 2" lens I have, the crack was caused by something burning to and overheating the lens. I used ZEP industrial purple cleaner, which has lye in it. And I know from using it on my pontoon boat's aluminum 'toons that it has enough lye in it to turn 50 series aluminum white.

I got most of the black off this lens awhile back, but doing so took the coating off around the area. And there was a tiny bit of black left over, you could only see when held in the right light.

What I did was submerge the lens in the purple cleaner, and let it soak for just under 50 minutes. I then used a New Hermes 'toothbrush' on it, also not recommended I'm sure...

The results? The lens is a clean as a whistle, the coating is completely unaffected by the lye or the brush. I took a series of before-during-after pics of the test. While the black smudge was easy to see by just looking at it, I could only find the black spot in one 'before' pic. And now, I can't find that tiny smudge of black anywhere, by eye or in the pics.

I took 17 pics, was going to post some but the board's upload window won't load...

[Dave Sheldrake]

a lot of western machine shave the lens epoxied into aluminium holders Kev

Run a Lye'd lens through a beam profiler, you may be surprised by the results

[Kev Williams]

I'm not advocating dunking an entire lens assembly into lye. Like I said above, ONLY the lens, like the pics. And anyway, if the lens is "toast" as described earlier in this thread, then other than an ounce of Purple cleaner, what do you have to lose? At worst you may end up with a serviceable spare. The lens in these pics, bad as it looks, engraves just fines. I have two other 2" lenses, but I HAVE broken 2 lenses in one day before, and this one will work fine if I need it..


These are 'before' pics. Notice the hairline scratches visible when the light hits just right.

lens2.jpg
lens3.jpg
lens4.jpg

This is the pic that shows the black spot, and the 'bald' area I created trying to clean it previously.

lens6.jpg

After 50 minutes, and the brush I used

lens11.jpg


-and the 'after' pics. The lens is very clean, the black spot is gone, and the hairline scratches don't appear any better or worse.

lens12.jpg
lens14.jpg
lens16.jpg

[George M. Perzel]

Kev;
I echo your comments - what do you have to lose?? I have used regular kitchen variety oven cleaner on lenses for at least the last five years and have reused the lenses with no negative results . I just soak the lenses, not the holder, and rinse and wipe gently-no need for a brush.
Of course the lens mfrs and laser suppliers are going to suggest you use nothing more abrasive than hummingbird eyelashes...fear is a very effective marketing tool and their motivation is to sell more lenses at the 1000% markup common in the industry.
I am curious as to whether any of the naysayers have tried to clean a burnt lens and had negative results? What was used and how??
Best Regards,
George
Laserarts

[Craig Matheny]

I have had lenses look like that and have used 3 different things to clean them first 90% rubbing alcohol second acetone then grain alcohal (ever-clear) If that does not work then you have the ever-clear to take the edge off of the cost for the new lens