Info about lens fungus from professionals

Hello.

Being contracted by local university for certain equipment repair, I had chance to talk to very skilled and experienced microbiologists there, who deal with fungus and other small nasty things. We had a pleasant talk about fungus that happens in lens, and they told me some pro-grade recomendations how to deal with it. We even were able to determine the long, hairy-patch style fungus genius (forgot it's name but it was of pennicilum breed or family, not strong in biology).

So, some info about fungus from pros, how to remove it, do's and dont's:

Don't forget!

Fungus is very stable, it has very nicely "protected" cells and nature worked on this protection for million years, so:

Commmon methods that don't work:

1. Alcohol won't deal ANY noticeable damage to fungus at all, even 99% medical grade one.

2. So does nothing vinegar or other consumer grade acids. Of course, fuming nitrous acid or any other super strong acid will kill the fungus, but your lens multi-coating will follow fungus shortly.

3. UV/Sunlight exposure is surely great and helps a lot, but for complete eradication, you'll need so long time, that such prolonged exposure to UV/Sunlight, that will certainly cause irreversible damage to your lens components, causing discoloration.

Exotic ways:

1. Ionising radiation, such as X-ray and gamma rays. You should consider that fungus will witstand 10000 Roentgen with ease, and that is not the power you're going readilly to find somewhere around.

2. Iode fumes will definetly kill the fungus, but it will readilly stick to your lenses, making them permanently brown.

3. Strong oxidizers, such as industrial-grade acids, Nitrous Oxide and Hydrazine will do the trick, but they will etch lens too.


So, you might think, there's no solution?

Sure it is!

It is any alkali detergent, which does not contains additives such as aromatisers or "surface active ingredients". In plain words, old caustic soda, used to clean clogged sewer, will do the best, and be the least agressive to glass. But don't forget, after treating lens with caustic soda solution, you need to rinse surface with plenty of deionised water. Failure to do so, may cause appearance of irremovable white deposit on lens surface. And remember, warmer the water, better the result. But don't pour boiling water, just temperature you're able to witstand with hand, will be ok.


Please note, all above is for KILLING the fungus, including it's spores, so it won't grow again after removal. And removal can be done using any convient way you have access to.

Yes, I asked that, and speaking with simple language, they said that fungus can't distinguish sonnar from plannar, APO from MD mount and so on to choose place of living according to that. All fungus needs is a bit of humidity and microscopic amount of organic for feeding. Why it get "stuck" at lens? one of possible answers was that fungus spore was intaken by moving air, and since lens surface is not perfectly flat, there was small dent or surface irregularity, to which spore stuck on. This also explains why there's glass damage under fungus - glass might was non-perfect at that area already, so fungus just worsened the conditions.

Regarding the genus or genius, you might be correct, I'm not that strong in Latin. In fact, they wrote the name of that patchy fungus on paper, but it was latin, and so unreadable for me, that I already misplaced it :(

I would be a little cautious about using strong alkali on a lens. It can and will etch the glass. As long as it is used and removed right away it should be OK but long exposures (no pun intended) should be avoided.

It would be interesting to find out how companies that deal in used lenses remove fungus.

The fungus removal means treating raw glass removed from the lens, without making contact with other materials.

P.S. They have some specific solution that they use for immersion microscope lens cleaning, but no idea whenever it is usable for normal lens.