Death by UV

[colinbm]

See how microbes perish under UV light.

 

[nfoto]

Rather, explode....

[Andy Perrin]

Pop goes the microbe.

[Nate]

That was pretty cool. It was something I was curious about too.

[Wayne Harridge]

Interesting video.  On a somewhat related topic, does anyone here know anything about the use of UV to stop the spread of fungus in lenses?  I've done a bit of searching on the internet and there seems to be a mixture of opinions.  I've recently acquired a 1960's vintage lens which has fungus inside and I'm just interested to know what to do with it (if anything).

[photoni]

11 hours ago, Wayne Harridge said:

use of UV to stop the spread of fungus in lenses?

My experience is with a brass lens from 1860 with a Petzval scheme , the first two lenses are glued
(I think at that time they used garlic juice or animal glue) I bought it at a good price because the doublet was partly opaque
I don't know if it was damp or fungus
in the summer I left it in the sun (to the south) 2 or 3 days ... the lens became clearer, not perfect but much better than before.

[photoni]

@colinbm only UVC?

[colinbm]

19 minutes ago, photoni said:

@colinbm only UVC?

Yes UVC as far as I know.

[dabateman]

12 hours ago, Wayne Harridge said:

Interesting video.  On a somewhat related topic, does anyone here know anything about the use of UV to stop the spread of fungus in lenses?  I've done a bit of searching on the internet and there seems to be a mixture of opinions.  I've recently acquired a 1960's vintage lens which has fungus inside and I'm just interested to know what to do with it (if anything).

Really depends on the lens.  Its possible the first couple elements would block all UV and not much would get there. Or they might transmit UV well and it could work.

Depends on the fungus too. Some are extremely resistant and would just go to spores and spread more. Or it could be sensitive and shrivels up.

 

I would try to see if its easy to take apart and clean each element properly. 

[nfoto]

I tried the UV exposure by sunlight method on my 360-1200 Nikkor, a rare lens I got very cheap as "junk" since it had sit unused in a damp cellar for 30 years and had heavy mold infestation inside. It worked -- until there was a sudden downpour and I wasn't at the premises at the time. My bad. I got a water-soaked lens instead. So I split the lens to get the water out, and at the same time wiped the front element of the zooming group (completely white with fungus) with a standard window cleaning flud. All the fungus disappeared immediately Dried out the lens thoroughly and put everything back. No more fungus inside and that is the situation 10 years later.

 

Basically, use your lenses on a regular basis and don't store them in humid conditions.

[ulf]

One problem with fungus infestation is that it sometimes eat/etch AR-coatings and even leave marks in glass surfaces.

If the affected surfaces can be reached by taking the lens apart the fungus itself can be cleaned away by sweeping the surfaces with suitable cleaning liquids.

 

 

[Wayne Harridge]

Thanks for the advice, on closer inspection it looks like the worst of the "infection" is on the inside of the front element so I should be able to get reasonable UV penetration.  It's sunny today so I'll try leaving it outside for the day with a piece of card over half the front element and see if I notice any difference.

 

[Wayne Harridge]

Ok, the lens in question spent 6hrs in the sun with a clear blue sky all that time.  I can't see any difference in the 2 halves of the front element yet.  Is it expected that the clearing of the fungus happens immediately or takes some time after the exposure to UV?

 

[nfoto]

Depending on the intensity of light received, days to weeks.

[Nate]

9 hours ago, Wayne Harridge said:

the lens in question spent 6hrs in the sun

I had a random thought about this. Would a magnifying glass, old school with no coating speed up the process?  I know they just take the light spread on the diameter and focus to a smaller area. Maybe don't do it to a pin point, but a cm or half.

[Wayne Harridge]

On 1/19/2022 at 4:27 AM, Nate said:

I had a random thought about this. Would a magnifying glass, old school with no coating speed up the process?  I know they just take the light spread on the diameter and focus to a smaller area. Maybe don't do it to a pin point, but a cm or half.

Yep, that would get more UV into the lens but I was already concerned about how hot the lens became with the sun baking!

I'm thinking now that I should just set it up in the garage for a few days with a black light bulb close to it.