Can the Right Kind of Light Kill Fungus?

<p>My Leica R 90 Elmarit lens arrived today, bought at a bargain price, and of course there's an issue (why does this not surprise me on an eBait auction). The front element has light fungus threads across it when you do the flashlight test, and the back has some fine haze from what is probably oil from the aperture blades. The rear isn't too bad at all, but I'd like to put the brakes on any further developments in that front glass. There's not enough to affect anything yet, other than probably having to watch where the sun is in the shot, but my idea was to shoot it as a portrait lens, so that isn't a big deal.</p>

<p>I read on the internet that people have killed lens fungus by exposure to strong UV light. Of course, I've also read about pesky alien invaders from Mars on the internet too, so who knows? Is this real science? Anyone tried this, and did the fungus really stop developing? These Elmarits are noticeably sharper than the 90 Summicrons wide open, so maybe a little stuff in there will mellow out the f2.8 shots anyway.</p>

<p>High intensity pulsed UV is used to kill bacteria and fungus. The same kind of exposure can etch polymers. The systems of which I'm aware are designed for commercial operations. They need professional installation and a thorough safety review. I wouldn't recommend them for an individual. </p>

<p>Sunlight has plenty of UV and we know that photographic lenses can be pointed at the sun. This may kill the fungus, but there are no guarantees. You should also be careful to position the lens so that there is nothing at the focal point. Anyone who has played with a magnifying glass in the sun knows that you can start fires this way. </p>

<p>Sufficiently short wavelength UV light may kill the fungus, but it may also be mostly absorbed by the glass of the lens element. Since fungi routinely survive in the wild where they get sunlight here and there, I kind of doubt that exposing the lens to the sun will kill the fungus.</p>

<p>Peter raises a good point. Fungus seldom grows in open sunshine, but since the fungus is on an internal surface, the UV absorbed by the glass will reduce the effect. Most glass cuts off around 350 nm. This still lets some long UV through. </p>

<p>Is there anyone with actual experience removing internal fungus?</p>

<p>Internal fungus comes in several varieties, so one answer doesn't fit all cases. If it has been around long enough, it can etch the glass....this is not good, and unless you want to spend the big bucks to have your glass resurfaced, is irreparable damage. A small spot, without threads might be removed, and there is lots of anecdotal evidence that people have been modestly successful in doing so...mostly on inexpensive lenses, and there is little evidence of the permanence of such solutions. A better alternative, but much more expensive, is somebody with lots of professional experience, who can also, upon reassembling the lens, ensure it is properly adjusted and all fittings are proper and within factory tolerances. The sunlight trick is really a better solution for removing the brown changes in balsam between lens elements in several 1950s era lenses which had thorium in the glass. It sounds like you picked up a "bargain" which in order to perform at its best, will cease to be a bargain when you factor in a CLA. You could use it as is, but don't expect exceptional Leica quality results with a lens which has been compromised until the lens is brought back to factory specs..</p>

<p>Sounds as if it's possibly an urban myth then. Like Peter, I was wondering about the lens glass itself absorbing most of the UV. Well, even w/ a CLA it's a bargain, but I'm in no hurry to send it out just yet. I'm going to try setting it in the sun often (we're in Florida, so this part will be easy), and ck on it regularly to see if it's getting any worse. I suspect it's going to test very well even w/ these issues. I once owned one of these with serious haze internally, and it was still one of the sharpest lenses I've ever shot. </p>

<p>I recall reading that negative air ionizers is a surefire way to kill fungus and bacteria on optical instruments; can't remember the source, though. The article described a small gas-tight chamber housing a personal ionizer and the infected optical instrument. </p>

<p>Sounds very plausible. Air ionization has been used extensively to "clean air" and one of the few effective non-contact methods that doesn't involve nasty chemicals:<br>

<a href="http://www.newscientist.com/article/dn3228-air-ionizers-wipe-out-hospital-infections.htm">http://www.newscientist.com/article/dn3228-air-ionizers-wipe-out-hospital-infections.htm</a><br>

<a href="http://www.newscientist.com/article/dn3228-air-ionizers-wipe-out-hospital-infections.htm"> </a></p>

<p>By the way I have a personal air ionizer somewhere I bought years ago. It's about the size of an external hard drive case and operates from a small 12VDC adapter. </p>

<p>Internal is a high voltage multiplier (basically a bunch of diodes) to bring the output voltage to a few KV. The output is connected to something that resembles a steel wire brush bottle cleaner with thousands of contact points to ionize the air. It's passive in that it's not fan-assisted.</p>

<p>I don't know if these things are still sold but it's conceivable to place it in a plastic box with an infected camera lens, and I can't see any harm that can be done. </p>

 

<p>Just an FYI –<br>

Negatively charged ionization wires generate the ozone. Depending on voltage, humidity and other factors, nitrogen oxide compounds can form too. At my work facility we use coronal discharge to apply potentials to photoconductors for measurement purposes. The enclosed ‘test box’ generates healthy amounts of ozone. After a few weeks of exposure, various rubber/vinyl/polymers in that cabinet begin to get gooey or ‘dry out’ and crack. The effect is rather obvious and leads to issues of insulation degradation and damage. So, just a word of caution about exposing things to ozone, don’t overdo the concentration nor go for a ridiculously long exposure window. I haven’t observed any problems with our setup in anything less than a week or so.<br>

Jim</p>

<p>Here's a typical Google result ... for some $$$ (I have no affiliation with the device/company nor am able to state effectiveness)<br>

<a href="http://photipherals.com/listing/trioxygear-i-anti-fungal-unit-for-non-sealed-optics-camera-bodies/">http://photipherals.com/listing/trioxygear-i-anti-fungal-unit-for-non-sealed-optics-camera-bodies/</a></p>

 

<p>Light can <strong>kill</strong> fungus in a lens, it might take a while, I left an old Cosina 28mm in the window for a month or so and it halted the growth of the fungus. However, it cannot <strong>remove</strong> the fungus, it has to be physically wiped from the glass to do so. I also won't rule out spores hiding in areas of the glass (like the internal baffling) where UV light won't reach them. Furthermore, fungus can etch glass, depending on how bad it is. As noted, glass does absorb a significant amount of UV, if you use a strong enough source, that small percent that gets though should kill the fungus. Ultimately, while light might kill the fungus, it still is best to clean it off by hand.</p>

<p>Sure, UV light can kill fungus, but what if you have some fungus in parts of the lens where light can't reach? Will you have achieved anything useful?</p>

<p>Sure, ozone can also kill fungus, but what if you can't effectively get the ozone inside the lens (which you probably can't)?</p>

<p>There's one way you can kill the fungus. Heat travels readily through the lens. At a modestly high'ish temperature, you can denature the proteins of the fungus, thereby killing it. I'd suggest about 130 deg F for a few hours. That's the temperature used to kiln wood when sterilizing for certain fungi that discolor and weaken the wood. This temperature should not be harmful to the lens. If this temperature scares you (which it really shouldn't), I would think maybe 115 deg F would also do the job.</p>

<p>Sarah's concerns about getting either ions or O3 inside the lens are right on the mark. </p>

<p>On almost all solid surfaces, ions recombine on virtually every collision with the surface, and on most surfaces, ozone is catalytically decomposed back into ordinary oxygen. If you don't disassemble the lens, gas going into the lens will have to pass through narrow passages and thus is certain to come very close to solid surfaces, so the probability of collision with the surfaces of the passages is extremely high if the flow rate is slow. </p>

<p>However, if you first put the lens in a vacuum chamber and then refill the chamber (and lens) with air containing a fungicide, you at least stand a chance of getting some of it inside the lens.</p>

<p>That being said, unless essentially every spore is killed, re-growth is very likely.<br>

<br />There's lots of material available on this topic and lots of potential health hazards. Try http://www.unesco.org/webworld/ramp/html/r8809e/r8809e07.htm as an intro.</p>

<p>Again, as Sarah suggests, heating (with cleaning and re-lubrication possibly needed) is likely a much better option than either UV or a chemical fungicide.</p>

<p>Tom M</p>

Heat makes lubricants go places where you don't want them, it makes lubricants change chemically (or speed up the process), and it makes lubricants evaporate and (later) condense on every surface the vapour can get to (if you thought that fleck of fungus was bad, how about an oily haze on every surface of every lens element?). Heat will put stresses on metal, and glass. It will affect paints too. The cement used to join lens elements as well.<br>And at the moderate temperatures suggested, even help increase fungal growth.<br><br>Low temperature (think 50 to 60 degrees Celcius, 120 - 140 F - enough to do damage to your lens) sterilisation will only work when combined with things like formaldehyde or ethylene oxide.<br><br>It is the cheapest option, by far, to have a fungus infected lens cleaned profesionally. Much cheaper than have a lens that went through that sort of kiln treatment cleaned, adjusted and fixed.<br><br>But we should not shy away from experiments. So Sarah, take your best loved lens, put it through the treatment you suggest, then report back. ;-)<br><br>UV will work. It will only get to places it can get to, obviously. And you need a lot of UV to get a small but working amount through glass. But it will work. And need repeating; best is to have the lens cleaned.

<p>If sending it in to get it professionally taken care of seems like more than you were looking to spend there may be a low cost method may work for you. Fungus needs a certain minimum humidity to grow, under that some will go dormant others can be killed with dry enough air for extended periods. I live in Costa Rica and humidity is a problem 8-10 months out of the year. I have been storing my lenses in air tight polypropylene containers with a generous amount of silica gel to keep them dry and to dry them back out after I've used them. In the 3 years that I've been doing so I haven't noticed any negatives to doing so. I have humidity indicator strips in the containers that show I maintain a relative humidity below 10% and I wouldn't doubt that it is very close to zero moisture after I've recharged the silica in the oven.<br>

Potential concerns would be the plastic containers could be giving of some volatiles that could condensate on the optical surfaces, as of yet I haven't noticed this though. Another is that I've read that lens manufacturers have a minimum humidity level to store lenses at in order not to dry out certain components. Don't know how much truth is in that statement, but on my modern lenses (none older than 10 years) I've not noticed functional differences other than what I consider normal wear( focus mechanism getting a bit looser for example). And I doubt that they used anything that can absorb/give off moisture for lens construction.<br>

It's worked for me to prevent fungus from even showing up even though sometimes I have seen light condensation on the inside of the lens after getting back from a hike a few times. I simply swap the moist lens for a dry one and in an hour the lens has completely dried out.<br>

If you do choose to go this route, I'd suggest flower drying silica that you can buy in 5lb boxes at craft stores. It's the cheapest per pound that I found. I pour it into small canning jars and replace the metal cap with a piece of Tyvek. Works great and I can put the whole thing in the oven to drive out the moisture once it's stopped keeping the humidity level where I want it.</p>

<p>The heat idea has potential, although I want someone to stop me if you ever see me putting a Leica lens into an oven. There's just something a little spooky about that, especially since I burnt our garlic bread to a crisp in that oven last night.</p>

<p>I'm not sure that removing humidity is going to work once the fungus begins, as it generally likes to grow between two cemented optical elements.</p>

<p>Thinking out loud: </p>

<p>Unless lens fungus is of some exotic variety that doesn't need oxygen, we can probably kill it by placing a lens in an atmosphere devoid of oxygen - maybe nitrogen or simply burn off the oxygen in the trapped ambient air. </p>

<p>Michael's idea sounds promising. Welding supplies sell clean dry nitrogen for shield gas. The initial investment in the tank isn't cheap but after that you can swap an empty for a full one relatively cheap if you go to an industrial welding supply. Running a hose into an air tight container and purging the air out before sealing it would probably get the oxygen levels low enough to at least make the fungus go dormant. And a large tank would last a really long time.</p>

<p>Siegfried, I remember an old high school experiment to measure atmospheric oxygen level. </p>

<p>A test tube is placed inverted in a pan of water. Inside the test tube is a small wad of steel wool. The idea is that the steel wool will oxidize thereby depleting the oxygen, and the volume-displacement of water in the test tube represents the oxygen level. </p>

<p>There are other considerations of course, but it might be a possible to do this in a simple Thermos bottle big enough to accommodate a lens. </p>

<p>Michael I'll do you one better, hand warmers. The type that you open the air tight package and give them a good shake, they're filled with a mixture of iron, salt and a couple of other ingredients to give a quick oxidation of the iron once exposed to oxygen(hence the heat). They are relatively cheap and I'm guessing would absorb most of the oxygen in a small container. I'm not sure though at what oxygen concentration the reaction would cease but my guess would be at levels below what fungus would need to continue growth.</p>

<p>Brilliant! Much faster than waiting for steel wool to rust. :-) </p>

Fungus will survive without oxygen. Even if not the fungus itself, the spores will.<br><br>Do you know how long a fungus can 'hold its breath', and how that compares to the length of time you are willing not to use the lens being treated, and to how long you can keep the the thing in an oxygen depleted environment?<br><br>Heat treatment is still a bad idea.

<p>Q.G.<br>

I realize this isn't something that would reliably kill the fungus, but I think it could halt it's advance. Fungus does need a certain set of conditions in order to grow (humidity, oxygen, temperature) and they all have to be within the limits for it to continued growth. If you can nudge at least one of these out of bounds it will at least go dormant, if not eventually die. Also, and this is complete conjecture, but I think that for the fungus to come out of dormancy the conditions would have to be close to optimal. So if the OP is planning to only occasionally use this lens and otherwise store it under conditions that are outside of the zone for fungus growth he should be able to keep it from doing any further damage.</p>

Siegfried,<br><br>The thing is how long "eventually" will be. How long are we willing, and able, to keep a lens in an oxygen-free environment?<br><br>It's of course correct that the conditions have to be good enough for the fungus to start growing again.<br>The fact that it's there to begin with tells us that at one time, they were indeed good enough. So if a change in environment is the thing that will have to stop the fungus, it will have to be a permanent change. Taking away oxygen for only a while will not help.<br>And if another change, one that can be 'more permanent' (i know...), has to be made as well, we can ask ourselves why go through the trouble of putting the fungus into 'stasis' using other non-permanent measures?<br>But yes, keeping the lens dry and sunny will help.

<p>This is probably an academic discussion since no research has surfaced that we're aware of on the types of fungus and its propagation which typically attack optical instruments, but I think there's a consensus that the only real fix is to dismantle the instrument and resurface its elements which probably isn't practical in the case of consumer camera lenses. </p>

<p>In the alternative, the only real option is to minimize its rate of propagation which established storage methods already addresses and any further intervention probably won't make much of a difference anyway. </p>

<p>It's still fun to think about, though. </p>