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Natural Science Forum / Physics / Optics / December 2008Feather tracks in lens coatings - any preventative?
Feather tracks in lens coatings - any preventative? Slightly off topic as this lens coating is on a camera lens, and I haven't yet seen such damage on any of my own microscope lenses. Under the microscope these tracks look like a powdered hoare frost in the coating and are usually called fungus - I don't know if this would be a correct term as it may be chemical reaction of some sort rather than biological but it does seem to spread very slowly from a point (either damage or an inclusion or weakness in the original multi layer coatings rather than from origination randomly across the lens surface. I once had a JVC video camera whose lens was completely destroyed by this type of damage in only a few years. The particular lens in question is a 1.4f aperture OM lens (1970s?)and the film facing lens is the one with a tiny area of fungus which I'm keen to halt (It can be seen with a loupe). Is there any preventative action to stop the deterioration, antifungal treatment or UV, IR radiation etc.? Obviously damage already done cannot be undone economically. Charlie+ > Feather tracks in lens coatings - any preventative? > Slightly off topic as this lens coating is on a camera lens, and I [quoted text clipped - 6 lines] > coatings rather than from origination randomly across the lens > surface. I've yet to see much real scientific analysis of what is called lens fungus, but after examining several victimized lenses, my suspicion is that it is indeed a fungus. Now anything growing has to have food and specifically nitrogen to live and grow, and in the case of lens fungi this seems to be either dust collected in corners of the lens assembly such as around the retaining edges holding lens elements, or maybe oil or other buildup on the lens surfaces. The branching pattern you describe seems typical of fungal growth. I don't believe the fungus eats the glass or coating itself; as a fungus it must survive on foreign animal or vegetable matter (which is the nature of fungi--they don't synthesize like plants or animals, just rearrange stuff from dead ones) contaminating the lens. Or perhaps oils or greases used to lubricate the mechanisms in a lens assembly. But the etching type damage occurs because the chemistry of the organism produces acids which then react with the glass or the coatings. It seems astonishing, but the energy represented in a little inert dust is transformed into destructive chemical action by a living organism. Given the exo-digestive nature of fungi, the destructive effectcs are not so astonishing. They're sort of an inside-out stomach lining. Prevention? Take away the food and/or moisture, or favorable temperatures. Cleanliness, dessicants. What I haven't figured out is why we don't see this same effect everywhere, just on lenses. Why not on glass windows or glassware in a cupboard? Or maybe I'm just not looking properly. Hi Richard, Windows are not coated with hard or soft coatings... the coating comes off from filters or lenses, because they are - I think "tempered" must be the right english word-. meaning that special surfaces have been added after the melting to prevent reflexions and blur. Far too expensive for normal windows. Colored windows are made like simple grey-filters, with ions -in- the glass. yours, heini > Windows are not coated with hard or soft coatings. I have seen severe cases of lens fungus that are etched much deeper than coatings, like it was sandblasted. My theory is that the fungus doesn't eat the glass or coatings, but dust or grease. The glass is etched by metabolic byproducts. The hyphae grow out onto the glass where there is no food, in tangled or branching patterns, like a feather or fern. A little knowledgeable diagnostic work would be good. Like a microscopic exam after a KOH wash, like is used for diagnosing human fungus infections. Thank you for your replies and theories, I am not a chemist or I would have a go myself! Do you think a broad spectrum antifungal cream for a few minutes might help arrest what already started if your theory is correct? I have taken a closeup of the particular patch (with a scale in shot) to try and get some Idea of the rate of spread at least, for my own interest. I probably will try to get a proper microscope photo but that is going to be difficult because of the depth of the lens assembly. >I have seen severe cases of lens fungus that are etched much deeper than >coatings, like it was sandblasted. My theory is that the fungus doesn't [quoted text clipped - 4 lines] >A little knowledgeable diagnostic work would be good. Like a microscopic >exam after a KOH wash, like is used for diagnosing human fungus infections. > Do you think a broad spectrum antifungal cream for a few minutes might > help arrest what already started if your theory is correct? You should be able to just remove it with normal optical cleaning methods. I should add that most fungus cases don't etch glass, so if you clean it off everything is OK. That's a problem when, for example, it is on the inside of a a multielement camera lens that can't be disassembled. No, this is definitely not cleanable by any normal method otherwise I would have done it, your term 'etch' (either into the glass or into the coatings) would be the correct one, and my OP was referring to this type of damage, sorry if it wasnt clear enough. If I manage to get it under a microscope I should be able to estimate the depth it has got to. >You should be able to just remove it with normal optical cleaning methods. > >I should add that most fungus cases don't etch glass, so if you clean it >off everything is OK. That's a problem when, for example, it is on the >inside of a a multielement camera lens that can't be disassembled. > > Do you think a broad spectrum antifungal cream for a few minutes might > > help arrest what already started if your theory is correct? [quoted text clipped - 4 lines] > off everything is OK. That's a problem when, for example, it is on the > inside of a a multielement camera lens that can't be disassembled. Richard, the kind of damage is not cleanable on either a camera lens or a microscope. The stuff is permanent. Please note that some honest vendors on various camera sites will disclose if a lens is etched. Frequently lenses used in Florida would be damaged by this process. Kevin Cunningham SMS Thanks Kevin for that post, your mention of frequency in Florida would indeed support that it may be a proper fungus, heat and damp being the drivers? I will give my antifungal cream idea a go I think and see if the growth halts on this lens which it would be a pity to lose, image will be softening no doubt with this problem but it is not really discernable in normal use at its present state, the damage is not central. Charlie+ >Richard, the kind of damage is not cleanable on either a camera lens >or a microscope. The stuff is permanent. Please note that some [quoted text clipped - 4 lines] >Kevin Cunningham >SMS Charlie, In my experience, my wife used to own 50% of a camera repair firm, the cream won't stop it plus you'd have refractive problems. What you might try is very carefully clean the lens, remove all grease and foreign stuff from the lens. Use a cheap LED flashlight, a small one, so you can shine a light through the class. Use alcohol and Windex or any quality water based cleaner. Then reassemble. Carry several water absorbing packets in your equipment case and the problem shouldn't re-occure. I hope. Thanks, Kevin Cunningham SMS > Thanks Kevin for that post, your mention of frequency in Florida would indeed > support that it may be a proper fungus, heat and damp being the drivers? [quoted text clipped - 12 lines] > >Kevin Cunningham > >SMS > Richard, the kind of damage is not cleanable on either a camera lens > or a microscope. The stuff is permanent. The fungus itself can be cleaned off. If it has etched the glass, then the glass is gone and yes, the damage is permanent. But fungus often grows without etching the glass, and cleaning is possible without permanent damage. This much I know from personal experience. Why it sometimes etches and sometimes does not, this I do not know, nor have I seen scientifically explained. Maybe it is the species of fungus, the humidity conditions, the type of food, temperature, how old the fungus has grown, who knows? It would be nice to know. As regards Florida, I have to stick up for my home and assert that humidity is a problem everywhere, because 60 percent RH is the magic threshold for fungal growth, and temperate climates are frequently above that. Indeed, Florida indoors can be dryer than up north, since people here inevitably have air conditioning. Northerners also have damp basements where they store things like cameras and lenses, which we don't have here. So except for desert climates, you're not immune or even less susceptible. Dessicants are not trustworthy, either. They all saturate sooner or later short of storing in a hermetically sealed container. Dessicants in a porous container are ineffective. And people believe containers are vapor-tight when they are water-tight, when it just isn't the case. Polyethylene film is vapor porous, for example. Dear Kevin and other members, There is an excellent way to check what the etching on the lens coating is and how it relates to the fungus and the kind of coating by looking at the "feather" pattern using a good SEM. There is a frequent contributor to this group who has assured me he will use his superb instrument to take a look, provided he is supplied with a suitable sample. Is there anybody in this group who has a piece of optical glass showing the discussed pattern which could be looked at using an SEM? Needless to say that this will be destructive testing, that is the sample will have to be taken apart und a small enough piece be obtained for the described purpose. If you have a sample and like to contribute it, please let us know. GR. > > Richard, the kind of damage is not cleanable on either a camera lens > > or a microscope. The stuff is permanent. [quoted text clipped - 22 lines] > are vapor-tight when they are water-tight, when it just isn't the case. > Polyethylene film is vapor porous, for example. > If you have a sample and like to contribute it, please let us know. I have the earlier described lens. They're about 10mm diameter glass elements that I could remove and send. They're heavily damaged on the edge, progressing to clear in the center, as if the fungus grew in the corners. As I also described earlier, the Martian fungus, or whatever it was, was thoroughly cleaned off, so only the etching remains. Anyway, it is junk other than its value as a fungus damage specimen, so you're welcome to destructively examine it for the sake of optical science, just tell me where to forward it if it sounds like a suitable candidate. (Email in above headers is genuine.) Unfortunately, the type of damage you describe originating from the edge of basicly badly kept lenses - is not the type of damage in my OP, where the damage occurs seemingly from a single point in the main area of a large element, which has been kept perfectly clean since inception, and there is no way any thing can be cleaned from the element by normal means, unfortunately this lens is still a very effective f 1.4 aperture 35mm lens and not available for destruction!. The damage extent would fit inside a 2mm circle and the area of the damage only a small percentage of that circle. The type of damage you describe below is something else probably and sounds definitely biological! Charlie+ >> If you have a sample and like to contribute it, please let us know. > [quoted text clipped - 7 lines] >where to forward it if it sounds like a suitable candidate. (Email in >above headers is genuine.) > Feather tracks in lens coatings - any preventative? > Is there any preventative action to stop the deterioration, antifungal > treatment or UV, IR radiation etc.? Obviously damage already done cannot > be > undone economically. In the past I sterilized my agar plates with a 100W Wood lamp, with good results. You can keep the bulb in a pot to protect eyes. >> Feather tracks in lens coatings - any preventative? >> Is there any preventative action to stop the deterioration, antifungal [quoted text clipped - 4 lines] > In the past I sterilized my agar plates with a 100W Wood lamp, with > good results. You can keep the bulb in a pot to protect eyes. H: I would guess you are talking about an ultraviolet lamp? It would not be difficult to search up what wavelengths would be most effective for this, if someone doesn't already know. As well, what about bleach on the lens or would that be ruled out because of collateral damage to coatings or superfluous to a UV treatment? Regards, Edward Hennessey >>> Feather tracks in lens coatings - any preventative? >>> Is there any preventative action to stop the deterioration, antifungal [quoted text clipped - 10 lines] > difficult to search up what wavelengths would be most effective for this, > if someone doesn't already know. I used to sterilize my agar for a couple of years with a so called 'blacklight', and this worked. Anyway, I googled and found that the best wavelenght for killing microrganisms is between 200 and 300 nanometers, so one needs a germicidal lamp (http://www.bbptraining.com/uploads/UVA_article_Oct06.pdf) ). According to a microbiologist, "UVA and UVB are not sufficient to kill fungus, they are quite resistant to UV, unless UVC (shortwave UV). You need at least above 100J/m2 UVC to kill 50% of the fungus" (http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00OjOb). Best regards h. > "Edward Hennessey" <halozzyzxhaloMINUS123@yahoo.com> wrote in > message news:x6KdnYUb49TGAsfVnZ2dnUVZ_gmdnZ2d@earthlink.com... [quoted text clipped - 26 lines] > > h. H: It came to me that another excellent resource to check would be art conservators. As they deal with objects of all kinds, glass and instruments among them and are very studied in my experience, my bet is they would have a number of operational procedures and literature references. Plus, they are some of the nicest people to talk with as long as one is courteous and focused. Regards, Edward Hennessey A very interesting tack to go down, thank you! I collect glass and some of it is hundreds of years old - not a sign of such fungus is visible, crystallization is the usual deterioration mode for ancient glass, though very difficult to tell the mechanism for glass that has been buried or sunk for a long time. My guess is that this etching fungus is a child of the low pressure vapor coatings age. Charlie+ >It came to me that another excellent resource to check would be >art conservators. As they deal with objects of all kinds, glass and [quoted text clipped - 8 lines] > >Edward Hennessey Hello Group, Am I very wrong in suggesting, that nobody in this thread has convincingly presented any evidence that the "hoary frost" is actually a fungus, that is a sapro- phytic plant? Could it not be, that it is the formation of microcrystals within the layers of coating which were applied to the lenses? GR. > A very interesting tack to go down, thank you! I collect glass and some of it > is hundreds of years old - not a sign of such fungus is visible, crystallization [quoted text clipped - 16 lines] > > > >Edward Hennessey > Am I very wrong in suggesting, that nobody in this > thread has convincingly presented any evidence that [quoted text clipped - 4 lines] > within the layers of coating which were applied to the > lenses? That's a genuine question, and why I suggested microscopic examination and the potassium hydroxide tests. Although I am equipped for this exam/testing, I don't have any "fungus" specimens at the moment; the one badly etched lens I had I disassembled and thoroughly cleaned before I got interested in the subject (indeed, this was how I became interested) (maybe someone has a lens ruined by fungus they want to contribute?). The thorough cleaning was applied because I believed the lens was fogged by some tenacious contaminant, and it wasn't until I had applied every polar and non-polar solvent and alkali in the lab supply cabinet to clean it off, that I took a microscopic look to see that the fogging was a very fine surface etch, in a pattern that suggested fungus growing in the edges of the lens elements where dust collected in this very old lens, and sparing the center of the glass. While I haven't done any serious research, if you Google, say, "lens fungus" you just get a lot of lore about the subject, nothing like an academic treatise, although such may exist. The casual evidence does strongly suggest actual fungus: required humidity, required presence of dust or contaminants, observed musty odors, macroscopic patterns resembling fungi, etc. And of course it may be possible that there is both true fungus *and* some physical crystalization process in various cases. Here's a Zeiss page on the topic, oddly following what I've been saying here: http://www.zeiss.com/c12567a8003b58b9/Contents-Frame/29cd78d56723da79c12571180042df52 Another idea that occured to me is whether the optically polished surfaces might somehow promote certain fungi to "creep". Most places fungi grow in nature are rough and porous, and maybe the organism "goes wild" when it finds something hard and smooth to crawl out on next to its food. Because you get fungus on lenses when other nutrient-rich objects in the same environment don't show it. This might explain the perception that coatings are feeding fungi, when they're not (and why would MgF, etc., feed fungi?). This sort of creeping behavior is a characteristic of fungi versus ordinary plants. Hello Dr. Kinch and Group, Please refer to the texts below for reference and perspective. I am glad you took my questions seriously. It is curious, is it not, that "fungus" on optical surfaces seems to occur only when optical coatings have been applied? Ordi- nary glass, uncoated lenses etc do not seem to show the de- scribed "feather tracks" thought to be characteristic of the fun- gal growth on camera and microscope objectives and eye- pieces. I never had the opportunity to see a fungus infested lens. I as- sume that the feather track pattern is similar to the growth of beautiful icy structures which one can see in wintertime on the inside of window panes. Such growth is also called dendritic growth and is typical of many microcrystalline structures. Un- fortunately I can't present images of such structures here. A magnificent reference with images can be found in Physics To- day, Nov. 2000, with the title "Diffusion Limited Aggregation: A Model for Pattern Formation". The images presented there are typical of the microscrystalline structures one can observe under the microscope formed under suitable conditions by most inorganic and organic compounds on the surface of glass. Images of fungus as observed in biological specimens and made visible under the microscope using verious methods of preparation can be found in the standard work "Principles and Practice of Infectious Diseases" by Mandell/Douglas/Bennet. These images do not look like feather tracks. It is possible that fungal growth provides the environment for microcrystalline formations by the creation of organic acids which, acting on the substratum of optical coatings leads to the formation of dendritic growth. It is also possible that the optical coating undergoes micro- crystallinization over time, depending upon its compostion and the exact mechanism of deposition. It may be worth while to use scanning electron microscopy to visualize the "fungal growth" on the surface of an affected optical element. Such an observation would almost certainly be able to differentiate between a microcristalline pattern and a biological skeleton. GR. > > Am I very wrong in suggesting, that nobody in this > > thread has convincingly presented any evidence that [quoted text clipped - 27 lines] > > Here's a Zeiss page on the topic, oddly following what I've been saying here: http://www.zeiss.com/c12567a8003b58b9/Contents-Frame/29cd78d56723da79c12571180042df52 > Another idea that occured to me is whether the optically polished surfaces > might somehow promote certain fungi to "creep". Most places fungi grow in nature [quoted text clipped - 5 lines] > This sort of creeping behavior is a characteristic of fungi versus > ordinary plants. > > Am I very wrong in suggesting, that nobody in this > > thread has convincingly presented any evidence that [quoted text clipped - 39 lines] > This sort of creeping behavior is a characteristic of fungi versus > ordinary plants. May I suggest an experiment? Put a fungus infested lens in a polythene container and microwave it! The polythene container should prevent arcing, and only water in the lens, viz that in the fungus, should heat up. Forseeable problems: Any moisture in the lens or between the elements might boil and explode! The microwaves might adversely affect the lens cement. Unfortunately, i do not have either a fungal infested lens nor a microwave oven, so i can't try it myself. It would be very unwise to try this on a lens with any residual value, as it will probably ruin it. However, it should kill the fungus and dehydrate it, making the mycelium shrink, perhaps to invisibility. Anyone care to give this a try and let us know what happens? If it works, it might be useful as a periodic preventative. (Oh dear - I believe Kevin has fainted!!!!) -hj Hi hj, sounds like a good idea at a first glance, BUT: metal parts in a microwave will fire sparks and make huge damage! Ever put a CD in a microwave? just heating up in a oven to 80 °C would sound like be a much better idea to me... without destroying too much, I think In conclusion, I think UV is the best thing to try. Wear eye and skin protection! yours, heini On 27 Jun, 10:58, heini <buerg...@physiologie.uni-heidelberg.de> wrote: > Hi hj, > sounds like a good idea at a first glance, BUT: [quoted text clipped - 9 lines] > > yours, heini Yes, but I think the heat might jeopardise lens cement. Also expansion within a tight mount might produce problems I suggested putting the lens in a sealed polythene food container in order to prevent the arcing you mention. Perhaps this would prevent the fireworks! Why not try it with a CD in a container, instead of a lens, and see what happens. Also, as you know, glass is generally a very efficient UV filter, and you would probably need to use a UV-C source to sterilise a lens with fungus. Ordinary glass transmits 250-100nm very poorly. Less of a problem with quartz glass. Personally, I wouldn't go near one of these sources without really meaningful UV protection........seriously dangerous stuff. Also, fungi are rather resistant to ionising radiation damage especially when dry and "resting" - probably the same for UV. Hell, chaps, let's do the experiment ! But only on a worthless lens!!!!!! hj > On 27 Jun, 10:58, heini <buerg...@physiologie.uni-heidelberg.de> > wrote: [quoted text clipped - 29 lines] > lens!!!!!! > hj Hi There, If you have access to a plasma etcher you could try this. Owen |
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