Fungus on a scope lens?

[363medic]

I was cleaning out some boxes of parts that I had and I found a Bushnell 1-4x LPVO that I had stashed away. I was planning on mounting it but then when I looked through it the internal surface of the optical lens appeared bubbled up (pic below). I called up Bushnell which wasn’t the greatest experience ever (if you have to talk to their customer service department choose the option to have them call you back, it’s not worth trying to wait on hold). At any rate they sent me a prepaid shipping label and I sent it back to them. I just got an email saying they looked at it and determined that it was fungus damage. They are supposed to be sending a replacement so other than an annoying experience getting in touch with them initially I am pretty impressed with their customer service.

Anybody heard of lens fungus before? I looked it up and apparently it’s a pretty big deal for telescopes and microscopes, but I couldn’t find anything related to weapon scopes.

 

[GymB]

This is why lenses are purged, nitrogen filled and sealed. You had a bad seal, brought it inside from the cold, and got some moisture inside. The fungus eats the coatings and etches the glass.

Big problem with old lenses that aren’t sealed.

 

[363medic]

Yeah it is nitrogen purged, but I guess for $100 you get what you get, go figure. I think the big culprit is that it was basically in an upstairs crawl space and the seals couldn’t handle the temperature fluctuations.