How to kill glass fungus

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Pau
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How to kill glass fungus

Post by Pau »

Dear lab experts:

I have some interesting vintage microscope slides highly infested by fungus, aparently similar to the ones that colonize lenses, so I'm highly reluctant to put them in my microscope before being sure that they can't spread to my optical systems and other slides.
I want to sterilize the slides with the minimum possible damage to the slides. The subjets are mainly histologic sections but someones are of mineral samples, all of them mounted in Canada balsam.
At my work lab I have access to an autoclave and to variety of chemicals.
I think the best way would be gamma rays, but I have not access to it.
If anyone has experience (methods..details..) I will be most grateful to his advice.
Last edited by Pau on Thu Apr 07, 2011 11:58 am, edited 1 time in total.
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Charles Krebs
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Post by Charles Krebs »

I've never seen a definitive answer. Many references to UV exposure. (But apparently the spores are the tough thing to kill off).

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Cactusdave
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Post by Cactusdave »

Normally fungus occurs on the glue used in dry mounts or more rarely in old fluid mounts. I've not heard of it occuring under the coverslip of a Canada balsam mount. Are you sure the fungus is really under the coverslip and not superficial on the upper or lower surface. I would clean the slides thoroughly and carefully above and below with 70% alcohol and then have another look at them. This should remove all surface contamination. If the minerals are dry mounts and not coversliped I agree that there is a very small chance of fungal spores getting somewhere you dont want them. However fungal spores need at least a trace of moisture/condensation to germinate. If you keep your microscope and objectives dry and at an even temperature you shouldn't have any problems.
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Pau
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Post by Pau »

Charles and Dave, thanks for your posts,

- UV light would likely damage the samples, in special the stains. I need to kill spores, it's the key to avoid contamination.
- Most fungal hifes are over the glass surface, only under the coverglass in points where it is separated from the cement.

I will try the autoclave sterilization, but I think the high temperature is going to damage the canada blasam.
A fungicide chemical that don't attack the balsam would be the best approach, but what one?
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Post by enricosavazzi »

Pau wrote:A fungicide chemical that don't attack the balsam would be the best approach, but what one?
You might try thymol first (it will kill growing molds but I am not certain it can kill spores). Thymol vapors act slowly, so you need to store the slides and a small amount of thymol in an air-tight container and let it work over days or weeks. Other than high temperature and intense radiation, I am not certain of a physical way to kill spores.
--ES

Tom Jones
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Post by Tom Jones »

Pau,

I really doubt you can actually sterilize the slides without making a mess of them.

Just clean off the outside of the slide with 5-10% bleach. It won't penetrate the mounting and kill anything inside though. Once you've done that, reseal the edge of the coverslip and you should be good to go. Nothing under the coverslip will get out, and probably wouldn't anyway even without resealing. If whatever is in there is alive, it may continue to grow, but unless it reaches the edge of the coverslip, nothing will get out.

If they were my slides, I'd store them seperately from my other slides to prevent cross contamination (only for peace of mind, really), and clean/reseal as above. Doing that, I think the odds of contaminating your optics during viewing are essentially zero. And to be honest, I think the odds are essentially zero even if you do nothing! I think most cases of contamination result from spores that are present in the original mount, not some that make their way in after the fact.

Tom

Pau
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Post by Pau »

Many thanks Enrico and Tom for your sugestions.
I will try the bleach bath, it's a very powerful desinfectant. It is to be seen if it don't destroy the canada balsam.
enricosavazzi wrote:(it will kill growing molds but I am not certain it can kill spores).
I prefer to protect the optics even if I finally ruin or throw out the slides
Tom Jones wrote:If they were my slides, I'd store them seperately from my other slides to prevent cross contamination Tom
They are now 8 km away in a closed box :D , but some of them were examined with one of my school lab microscopes.
Pau

Mitch640
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Post by Mitch640 »

What about UV light? Should not harm the slide itself, but should kill the fungus and spores.

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Post by enricosavazzi »

Mitch640 wrote:What about UV light? Should not harm the slide itself, but should kill the fungus and spores.
UV light (especially UV-C and UV-B) does not damage ordinary optics, and indeed does kill fungus and its spores. However, in this case the fixed tissues and pigments of the slide are likely sensitive to UV, and may degrade and discolor.

A further problem is that the slide glass and Canada balsam of the slide certainly absorb UV-C and probably also UV-B, so a strong UV source should be used. Transparency of ordinary glass to UV-A is somewhat less of a problem, but UV-A is also less effective for this purpose. Ordinary sunlight is probably insufficient.
--ES

Mitch640
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Post by Mitch640 »

After further thinking about the problem, I think, even if you do kill the fungus, that doesn't remove the effects of it. The damage is done.

You never see a camera lens that is used all the time with fungus. My theory is, that just the act of the lens being out in sunlight, or strong studio lights, is enough to keep the fungus from ever growing in the first place.

Lenses with fungus are almost always found in an advanced stage of infection, after being kept in cases and closets for years. I bet these slides were kept in wood boxes, maybe even with moisture absorbing felt liners, never seeing the light of day. A place fungus will love. :)

Harold Gough
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Post by Harold Gough »

I seem to remember, several years ago, seeing ammonia fumes (not the liquid in contact) recommended for killing fungi on lenses. I don't know how safe that is.

Harold
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realjax
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Post by realjax »

A while ago I got hold of a very cheap Componon-s 50mm. 'Its a bit dirty' the guy said who sold it to me. But some of the elements turned out to be heavily effected by fungus.

Since I paid so little for it I figured that a ruthless cleaning job could not make things much worse. So I went looking for some info on how to do this and found interesting techniques at the forum on mflenses.com

A few people there swear by cold creme as the miracle fungus remover. Throw in a bit of lighter fluid for cleaning off the creme afterwards and it's fungus-be-gone! Tried that, several times actually, but my element was beyond the handcreme solution. In the end the only stuff that actually removed the fungus was acetone.

And allthough this removed the fungus, it had been sitting there for long enough to completely eat away most of the coating of the lens element.
Funnily enough (it was one of the back elements) it still works quite well when used reversed..

Anyway, moral of the story: you might want to give cold creme a try. More info on how and what is here for instance.
Last edited by realjax on Wed Apr 20, 2011 12:50 am, edited 1 time in total.
Jacco

Harold Gough
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Post by Harold Gough »

I used the cold cream method to largely remove a black deposit from the rear element of a lens. It would not remove it all but the mark seemed not to affect images before being thinned down by my efforts, so I was fairly pleased. In any case the main feature of the lens was its optional/controlable soft focus.

Harold
My images are a medium for sharing some of my experiences: they are not me.

Craig Gerard
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Post by Craig Gerard »

Jacco,

Excellent information and link! Thanks :)


Craig
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