Smudge on side window

While cleaning the optics on my GF this morning, I noticed that a “smudge” has developed on the side window, just above and to the left of center. I can’t tell whether it’s on the inside of the window or the outside, but it doesn’t wipe off with a Zeiss wipe and it doesn’t look scratched. Here’s a photo:

I haven’t (yet) noticed any change in how the GF works, but wonder what the community experience is with this sort of thing. In particular, I’m wondering if the problem seems to get progressively worse until Bad Things happen. Or is it something benign I can ignore. If the former, maybe I need to buy a new window, just in case.

Thanks for the help!

It’s likely a bit of smoke/dust that’s starting to become burned onto the glass by the laser beam. It’s best to get it cleaned off now, or it’ll get worse.

That entire silver ring with the glass in the middle unscrews from the laser arm.

Unscrew it, and then use a q-tip dipped in isopropyl alcohol to rub it a bit harder. That will likely clean it off. Then screw it back in.

I’m pretty sure it’ll clean off fine, but you can always buy a replacement here:


For me ‘if it’s not broke, don’t fix it’ is my motto. I do think it’s a good idea to have one on hand. And, if you start to have problems, you may want to use some alcohol to ‘soak’ that spot and see if it will come off first. My thoughts…

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Dan do you use the cheap stuff or the good alcohol

I use 91% isopropyl I got at walmart

Thanks! Just what I needed to know.

@dan84 , yes, I’ll try the Q-tip and isopropyl alcohol trick. I think I’ll start with leaving the window in place and only remove the window if it doesn’t come clean easily. If it works, the optical path stays sealed. @rvogt ‘if it’s not broken…’ is my motto, too, but only to the first order. Second order: Do the PM, but don’t go crazy. :wink:

Thanks again.


A quick application of isopropyl alcohol (I had a bottle of the “good alcohol” on hand) with a Q-Tip did the trick. One swipe, no more smudge. Thanks again for the tip.


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