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View Full Version : Rehabbing a Black Lens?



Keith Winter
11-09-2015, 5:23 PM
My engraver forgot to turn on air assist for a job, the entire lens turned black. :eek: :( We tried to clean it with the regular solution and also with some acetone. Acetone got off some of the black in the center but a ring of black remains. I'm a bit hesitant to soak it in the acetone beyond a few seconds in fear of the lens coating coming off, has anyone tried soaking a lens in acetone to remove black spots? Any other methods that work to remove black spots?

See photo of the black on the lens below:
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Rich Harman
11-09-2015, 6:13 PM
I have soaked a lens in acetone before with no noticeable ill affects. With the lens submerged I have even scrubbed it with a Q-tip to get off stubborn stains.

Gary Hair
11-09-2015, 6:15 PM
You know that stuff you have with your eggs in the morning? Your lens is basically the same - TOAST...

Call on your (new) friends as II-VI (two-six), they will set you up with a brand-new lens.

Ron Gosnell
11-09-2015, 6:21 PM
It looks like you have nothing to lose at this point.
Soak it hope for the best, maybe you will discover a fix for the rest of us when we
forget to turn on the air.

Gozzie

Mike Null
11-09-2015, 7:26 PM
Toasted or fried--take your pick.

Keith Winter
11-09-2015, 8:51 PM
You know that stuff you have with your eggs in the morning? Your lens is basically the same - TOAST...

Call on your (new) friends as II-VI (two-six), they will set you up with a brand-new lens.

Haha! Yeah wasn't funny when it happened though, between this, a lens not getting tight enough and flying out a couple weeks ago, plus one Trotec original that came unglued and fell out and chipped while they were cleaning it, I'm down 3 lens in one month. Funny we've gone 3 years without ruining any and then last month lighting struck. Gonna try soaking it in acetone and see what happens... If I just go as is, think it might work since the middle is clear or will it just Crack if we try to use it as is?

Bert Kemp
11-09-2015, 9:07 PM
thats why my air, water and exhaust are all on one UPS I can't for get to turn it on.

Jack Clague
11-09-2015, 9:22 PM
Keith hope you don't mind me butting in here with another lens related question, I have got a very small and faint scratch on my lens, if I am not noticing any effect on the engraving and cutting quality of the beam should I leave it as is or would you try and remove the scratch in some way?

Rich Harman
11-09-2015, 9:33 PM
...if I am not noticing any effect on the engraving and cutting quality of the beam should I leave it as is or would you try and remove the scratch in some way?

If it aint broke...

If you don't have a spare, then I would recommend getting one, I would not attempt to remove the scratch. It could be you would notice a difference when you put a new lens in. When I first got my laser I treated my lenses extremely carefully. Now, not so much. My abused* lenses work just as well as brand new ones. Or at least there is not enough of a difference that I have to change my settings.

* By "abused" I mean cleaning them aggressively - but I'm still reasonably careful about it.

Keith Winter
11-09-2015, 10:03 PM
Keith hope you don't mind me butting in here with another lens related question, I have got a very small and faint scratch on my lens, if I am not noticing any effect on the engraving and cutting quality of the beam should I leave it as is or would you try and remove the scratch in some way?

Faint scratch should be no issue

Jack Clague
11-09-2015, 10:37 PM
Faint scratch should be no issue

Thanks guys, I'm pretty vigilante with my cleaning but i think it was caused by a newbie mistake of not having enough cleaning liquid on my lens or lint free paper, i'll see if I can get a pic so you can see it.

Would love a spare lens but at $420 a pop here in AU its a tight expense

Dave Sheldrake
11-09-2015, 11:27 PM
Would love a spare lens but at $420 a pop here in AU its a tight expense

(coughs a lung) HOW MUCH!!

Hummm drop me a directline Jack, I may be able to help on that one with an AU buddy called Stuart

Keith.....no...just noooooo

If you remove the AR coating by mistake backscatter can in theory damage your optical train (as well as launching specular reflections off into the scenery)(usually towards something expensive)

Keith Colson
11-10-2015, 4:42 AM
I see they have "HQ" lens on ebay for about 50 bucks. I need to buy one and try it out. The $20 mirror from I got from ebay works fine. Its a pretty cheap experiment. The OEM stuff is ridiculously priced. My Universal lens which is looking aged after 4 years of running is about double the price you quoted. I will order one soon and try it.

Jiten Patel
11-10-2015, 5:18 AM
There is a post on here about that very issue I had quite a while ago (can't find it sorry). You can get it off with a lot of scrubbing (delicate scrubbing). Took me a few hours, but managed to get it all off with no visible damage. I just used the Trotec solution and cleaning tissues.

Jiten Patel
11-10-2015, 5:20 AM
here you go - http://www.sawmillcreek.org/showthread.php?205561-Have-I-messed-up-my-lens-already

Keith Winter
11-10-2015, 8:22 AM
Good advance on the back scatter thanks! Dave if I accidentally remove the coating it will turn clear correct, is there something else to look out for I'm missing?

Dave Sheldrake
11-10-2015, 11:18 AM
The coating is clear it's the lens that has the orange hue :)

Keith Winter
11-10-2015, 11:29 AM
ok good tip! Thank you!

George M. Perzel
11-10-2015, 2:08 PM
Hi Guys;
Keith- Is that lens from your Trotec or Thunder?Looks like an ordinary Chinese one. I only use Chinese $40 to $50 lens in both my Laserpros and Shenhui. I have also suffered the same fate and had great results using Oven OFF cleaner. Get a small bowl, put the lens in it burnt side upon and immerse it in Oven Off. Keep it wet and after about a hour the burnt area should slough off (first time I ever remember using that word!). Yea, I know- there are some who raise alarms at using Oven Off as prolonged use will endanger the banded snail darter and cause the mighty redwoods to molt twice a year.......
Anyway, IMHO, the price of laser lenses promoted by the big guys (Trotec, Universal, GCC, Epilog, etc.) ranks right up there with breakfast cereal and hearing aids on the top ripoff list.
Best Regards,
George
Laserarts

Keith Winter
11-10-2015, 4:32 PM
It's a Trotec lens. Haha George, yes the prices they charge for the lens are a rip off indeed!

I tried soaking it acetone for an hour then using a sterile doctors swab on it (think giant q-tip). No dice on that, didn't do anything. Parts of the edges of the lens flaked off though from soaking. It looks even worse now around the edges, middle looks the same. May try oven off, but at this point I think I'll have to affirm what Gary said, it appears toast.

Also, at the same time I tried to remove my other damaged lens from it's holder by soaking it an hour too. The acetone softened the glue a tiny, but didn't even eat the glue off the lens holder, had to chip out my other bad lens.

Chris Corwin
11-10-2015, 4:41 PM
Instead of acetone to remove the lens from the holder, try lacquer thinner, but only if the holder is metal. It could melt plastic holders.

Paul Phillips
11-10-2015, 4:59 PM
Kieth, I wonder if an Ultrasonic cleaner would work? I have one I use for cleaning collets and bits for my CNC which cleans off the most baked on wood and Acrylic residue that gets built up, if you know of anyone who has one or maybe a Jeweler or someone like that would try it for you, just a thought!?

Henri Sallinen
11-12-2015, 4:42 AM
Definitely try the eBay lenses. We've ordered the HQ lenses and they we're about 30-35 per piece (shipping was free). Quite a lot different than paying 10x for a OEM lens. Quality seems the same, price not so. The order just takes some time to arrive, so if in a hurry, then this isn't your way to go.

Kev Williams
11-12-2015, 10:46 AM
What George said: oven cleaner. If lye won't take it off, nothing will, and it probably won't hurt the coating.

Or something slightly less drastic, Castrol Super Clean or Purple Power, they also contain lye.

Dave Sheldrake
11-12-2015, 5:49 PM
What George said: oven cleaner. If lye won't take it off, nothing will, and it probably won't hurt the coating.

Or something slightly less drastic, Castrol Super Clean or Purple Power, they also contain lye.

errrr no, sodium hydroxide will make short work of the aluminium holder !

Gary Hair
11-12-2015, 6:49 PM
errrr no, sodium hydroxide will make short work of the aluminium holder !

But when you eat away enough of the holder then the lens will pretty much fall out...

Dave Sheldrake
11-12-2015, 6:58 PM
But when you eat away enough of the holder then the lens will pretty much fall out...

true :) bit of a pricey way to do it though ;)

Dan Hintz
11-13-2015, 6:53 AM
But when you eat away enough of the holder then the lens will pretty much fall out...

Like dissolving a car's engine to get to that hard-to-reach timing belt :D

George M. Perzel
11-16-2015, 1:01 PM
Hi guys;
Ref: oven cleaner
My holders have removable lenses so not dealing with any metal.
Best Regards,
George
Laserarts

Kev Williams
11-16-2015, 3:48 PM
I kind of expected it was a given that you clean ONLY the lens...

Richard Rumancik
11-17-2015, 9:59 AM
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-Laser-Optics/co2-laser-optics_products.html

The cleaning info starts on page 14.

Gary Hair
11-17-2015, 3:23 PM
Maybe I missed it, but on what page did they mention oven cleaner?

Richard Rumancik
11-22-2015, 9:33 PM
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
11-22-2015, 11:50 PM
Nope, that was a rhetorical question.

Kev Williams
11-23-2015, 4:07 PM
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
11-23-2015, 4:34 PM
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
11-23-2015, 6:33 PM
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.

325750
325751
325752

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

325753

After 50 minutes, and the brush I used

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-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.

325755
325756
325757

George M. Perzel
11-24-2015, 12:13 PM
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
11-27-2015, 1:37 AM
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