Home

Please support mflenses.com if you need any graphic related work order it from us, click on above banner to order!

SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

UVC to kill fungus
View previous topic :: View next topic  


PostPosted: Thu Nov 10, 2016 11:21 am    Post subject: UVC to kill fungus Reply with quote

I was asked by a friend to help kill fungus in one of his precious lenses.
Came up with the idea of using a germicidal 254nm mercury lamp.

Setup consists of an aluminum housing (studio flash reflector) plus top
and bottom aluminum shield. Very important to get this as tight as possible
to protect any UVC from leaking that housing!



Most important fact is, that UVC is so much more efficient to kill as DNA is
being destroyed below 300nm. 1h at 254nm equals about 4000h at 365nm.



============================================================
!!!DON'T DO THAT IF YOU DON'T KNOW EXACTLY HOW TO PROTECT YOUR SKIN AND EYES!!!
============================================================


PostPosted: Thu Nov 10, 2016 2:19 pm    Post subject: Reply with quote

That should work very effectively for fungus on the outside surfaces, but most lenses have VERY poor transmissions of such short wavelengths.
Only 10% of the lenses I've measured has any measurable transmission (above background scatter) at 300nm and only one of those was above 0.25%
I don't think any showed transmission at 250nm (I didn't bother recording transmissions that far down) Even the wonderful 80mm El-Nikkor doesn't transmit at 300nm.

With partial disassembly it may prove a good option, but that may not make it any easier than chemical methods.


PostPosted: Thu Nov 10, 2016 2:27 pm    Post subject: Reply with quote

I dunno, Klaus . . though I might not understand. Assuming you are going for a kill without dismantling the lenses, many forms of glass have a 0% uv transmittance below about 300nm.

When I had a lens with severe fungus, I first took the lens apart, then exposed the first surfaces having the fungus directly to the UV, without them being protected by other elements of the lens.


PostPosted: Thu Nov 10, 2016 2:59 pm    Post subject: Reply with quote

Yes, this is correct, most glass does not permit UV beyond 300nm. Dismantling would be best.
However transmission is never zero, there is always some light that transmits, yet the dose is low.


PostPosted: Thu Nov 10, 2016 3:45 pm    Post subject: Reply with quote

I don't suppose you have a convenient 300nm source handy (or anything in the 300-330nm range) these would still give fairly good germicidal results while having a better chance of transmission.

We have powerful Lead elemental lamps, whose primary wavelengths are 217 & 283nm which might work better - not easy things to use outside of the instrument though.
Other elemental lamps (hollow cathode or electrodeless discharge lamps) that might be good are Tin (303 & 318nm) Copper (325 & 327nm) Magnesium (285nm)...
Better than any of these perhaps is a deuterium lamp (which is actually quite common in labs.) They give broad spectrum UV from about 160-380nm peaking around 240nm. I think they're somewhat easier to operate than EDLs as well!

Looking again at the nice plot you attached I see the vertical scale is logarithmic so, I suppose, even the difficult to measure transmissions might be significant.
Mercury vapour lamps do also put out weaker bands, 5 of which are in the 295-315 region.

Keep us informed on how it works - I might have a few lenses that would benefit from a few hours inside one of our spectrometers Smile


PostPosted: Thu Nov 10, 2016 5:46 pm    Post subject: Reply with quote

DConvert wrote:
I don't suppose you have a convenient 300nm source handy (or anything in the 300-330nm range) these would still give fairly good germicidal results while having a better chance of transmission.

We have powerful Lead elemental lamps, whose primary wavelengths are 217 & 283nm which might work better - not easy things to use outside of the instrument though.
Other elemental lamps (hollow cathode or electrodeless discharge lamps) that might be good are Tin (303 & 318nm) Copper (325 & 327nm) Magnesium (285nm)...
Better than any of these perhaps is a deuterium lamp (which is actually quite common in labs.) They give broad spectrum UV from about 160-380nm peaking around 240nm. I think they're somewhat easier to operate than EDLs as well!

Looking again at the nice plot you attached I see the vertical scale is logarithmic so, I suppose, even the difficult to measure transmissions might be significant.
Mercury vapour lamps do also put out weaker bands, 5 of which are in the 295-315 region.

Keep us informed on how it works - I might have a few lenses that would benefit from a few hours inside one of our spectrometers Smile


Thanks for that! I do have a few other suitable lamps, yet problem is to radiate for hours in a fully closed cabinet
which has to be large enough for the lens.

Also have a 30 Watts Deuterium lamp, jet is very expensive to replace the bulb and I don't want to waste it on such a project Wink

I have a very strong continuous Mercury doped Xenon lamp system (200 W) with lots of strong Mercury lines (esp 313nm) (it is mid pressure) with quartz fiber coupling, that might be best choice then.


(c)photonics.com


PostPosted: Thu Nov 10, 2016 10:58 pm    Post subject: Reply with quote

kds315* wrote:

Thanks for that! I do have a few other suitable lamps, yet problem is to radiate for hours in a fully closed cabinet
which has to be large enough for the lens.

Also have a 30 Watts Deuterium lamp, jet is very expensive to replace the bulb and I don't want to waste it on such a project Wink

I have a very strong continuous Mercury doped Xenon lamp system (200 W) with lots of strong Mercury lines (esp 313nm) (it is mid pressure) with quartz fiber coupling, that might be best choice then.


(c)photonics.com


I thought you must have better options available
D2 lamps aren't cheap I know, I think our last replacement was £478 via a third party supplier!

The doped Xenon lamp sound interesting with one of those I might finally be able to start seeing some UV with my converted camera. I bet it falls outside my projects budget though...


PostPosted: Tue Feb 01, 2022 12:02 am    Post subject: Reply with quote

Resurrecting an old thread. I am trying to see if I can kill some fungus in a few of my lenses. My record with lens disassembly and repair isn't great so I wanted to see if I could kill spores inside of a lens with a UVC light. I went ahead and bought this one that claims to be 254nm: https://www.amazon.com/gp/product/B08JNPK13Y

But I never considered that UV light transmission might be so limited in a standard lens. I wish I had seen this post first. I did see a YouTube video in which someone stopped some lens fungus from advancing, but perhaps this was only possible because it was on the back of the front element?

https://youtu.be/wCFh-GvVR6o

If I left the light on for, say, an hour, or even overnight, would that still not be enough to kill any spores? Or are there any widely available 300nm+ lights/bulbs that are new to the market since this thread was started in 2016? What about the B+W UV-Pro?


PostPosted: Tue Feb 01, 2022 10:03 am    Post subject: Reply with quote

At 254nm the transmission of usual glass especially with AR coating is very, very low. So I would say this is not very helpful for stopping the fungus groth somewhere deep in the lens system.
Additional, you would only stop the groth, but it will likely not chnage its apperance, So it will sit there for decades to come.

So perhaps better learn on cheap lenses how to work on lenses?
With visible blue / near visibel UV the transmission would be higher, but the effect on the fungus is likely low.


PostPosted: Tue Feb 01, 2022 10:53 am    Post subject: Reply with quote

A problem with killing fungus this way:

- Low UV transmission in the glass (as discussed above), so if the fungus is deep inside a cell it will take a long time
- Not 100% effective; let humidity levels creep up above 65% RH again for more than a week and the fungus will come right back
- You really need to disassemble the optics anyway to clean the glass of the fungus' metabolic by-products, acids in particular

Killing the fungus seems intuitively the right thing to do, but it is not very effective. Once you have cleaned the glass, really the key to controlling fungus is storage conditions:

- Keep it dry; below 65% RH spores don't germinate, below 55% RH already growing fungus goes dormant
- Don't provide a food source; keep the glass clean from contamination such as dust and skin oils

A single day of high RH is not a problem; spore germination requires around a week of consistent high RH, so happily use it on a humid day but bring it back to dry conditions as soon as practical.


PostPosted: Wed Feb 02, 2022 7:24 am    Post subject: Reply with quote

Super useful replies, especially about the relative humidity numbers. I went ahead and bought a hygrometer so that I can get a sense of what the humidity is like in my home. I was hoping that UV could at least help me buy some time but it seems like a dry cabinet may be the next step, unless I want to try to clean the lenses myself. Thanks you both!