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How common is fungus between cemented elements?
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PostPosted: Sat Jul 03, 2021 11:13 pm    Post subject: How common is fungus between cemented elements? Reply with quote

Was cleaning a lens today, and the first time I ran into fungus between cemented elements. Is this very common?


PostPosted: Sat Jul 03, 2021 11:39 pm    Post subject: Reply with quote

Not super common, maybe 10% but probably less of fungus cases will effect the doublet's common surfaces, I'm not sure if the balsam is food for the fungus, I don't think the new UV curing glues will be a food source, I've not had many lenses infected, and those that were were newly infested or lightly infested, and usually the first inner surface from the end.
The moment you discover fungus you should expose the glass to UV light to kill the fungus.


Last edited by Lightshow on Tue Jul 06, 2021 9:48 am; edited 1 time in total


PostPosted: Sun Jul 04, 2021 11:38 am    Post subject: Reply with quote

Every time I have had haze/similar of a doublet I have attributed it to cement deterioration, not fungus. It seems most unlikely to me that spores could have penetrated the cement.
Perhaps you could post a pic - tendrils creeping in from the edge would be quite convincing...


PostPosted: Mon Jul 05, 2021 8:54 am    Post subject: Reply with quote

I have a Jena Pancolar 50 1.8 with a few tendrils, and they are in the cemented part, between glasses. Growing from the sides to the center. Fortunately, they are quite small so I don't really notice them in the pictures. I gave it a nice sun bath, hopefully that killed them (although I expose it to the sun every few months: easy and for free).


PostPosted: Mon Jul 05, 2021 11:46 am    Post subject: Reply with quote

Unfortunately I reassembled the lens. I guess it could be cement deterioration, but normal delamination is the fernleaf patter commonly seen on old binos.....

I wanted a gauge on this as I buy more old glass for cleaning and repair, I think I will keep in mind that there is a say a 10-20 percent chance its something not cleanable..... Thanks


PostPosted: Tue Jul 06, 2021 9:46 am    Post subject: Reply with quote

Discriptions/pictures will be your best tool to avoid the worst ones, new fungus is fairly wispy, you really have to look for it, so the average seller may miss it.


PostPosted: Tue Jul 06, 2021 9:54 am    Post subject: Reply with quote

marcusBMG wrote:
Every time I have had haze/similar of a doublet I have attributed it to cement deterioration, not fungus. It seems most unlikely to me that spores could have penetrated the cement.
Perhaps you could post a pic - tendrils creeping in from the edge would be quite convincing...

The spores won't penetrate anything unless there is an opening, the fungus can and will penetrate solid rock, so balsam will be easy in comparison.
https://en.m.wikipedia.org/wiki/Lens_fungus
https://www.sciencemag.org/news/2016/03/iron-eating-fungus-disintegrates-rocks-acid-and-cellular-knives