Here is a recent posting from the Canon FD listserver that ought to give the
last word in lenses and fungus. I've never seen such a comprehensive write
up on the problem:
***************
From: snaver@xxxxxxxx (Dr. Richard H. Evans)
Posted on: canon-fd@xxxxxxxx
Years ago I put my talents as a veterinary pathologist to work when I
noted fungi on the lens of my old Canon Ftb and Nikon microscope lens
after they were stored for 2 years. I went hog wild and looked at other
lens I had and used often and new ones friends had just bought. I found
out the ALL lens even brand new ones come with fungal spores floating
around in them. Now - given increased humidity and darkness they can
sporulate and grow hyphae (called vegetative forms as the grow and
produce kids) along the glass, producing millions of spores which
themselves sporulate if the conditions continue and result in those
beautiful tints.
Further, the older the lens, the easier it was to flunk the pressure
smoke test indicating the lens compartments were not sealed (smoke would
enter the interior of the lens when passed over the lens under
pressure), allowing air in with all the bugs it carries. Many of the
lens I used came from a camera store in Northridge, CA after the
earthquake. Several of the brand new ones developed colonization by
fungi released from the earth during the quake. This makes me wonder
just how tightly the are sealed.
Last year at the request of a friend who owns a camera store, I cultured
the front glass of 20 used lens and 20 brand new, never out of box lens.
All 20 used lens had on average 6 species of fungi, while the new lens
average 1-3 species, until left out of the box for 24 hours, then they
ranked as high as the used lens. I am not going to tell you the number
of fungal species on the hand of my friend, he is still in shock today,
claims "he fells dirty all the time" since I entered his shop.
As a remedy, I tested desiccant packs and found most CONTAIN fungal
spores and actually very poor moisture 'suckers' as Klaus remarked.
I tried a myriad of antifungal agents. Alcohols such as ethanol were out
because as Bill says the require soaking which does a job on internal
portions of the lens and they do not kill many saprophytic fungi.
Hydrogen peroxide is usually thought of as a sporocidal agent, but it
ain't necessarily so. Many species spores are not effected by it. Except
for UV, almost all other commercial agents require the item be immersed
in it. However, the organic aldehyde disinfectants (actually sterilants
- such as those used to sterilized medical instruments that can not be
autoclaved) were the choice as their vapors in sufficient concentration
kill fungal spores not to mention everything else. The two most common
are formaldehyde and gluteraldahyde.
I built a airtight box and placed lens in it on a rack with a small dish
of gluteraldahyde in the bottom and put the whole affair out in sun for
3-4 hours to get temp up. The gluteraldahyde vapors did the trick. End
results were that when then the old lens was disassembled in a sterile
environment, it was sterile. I tried this procedure with 6 other used
lens and the effect was the same except 3 of them developed weird
dicolorations and 2 actually fell apart. The gas probably acted as a
solvent, dislodging all manner of important things.
Radiation - sounds great, but it is dose dependent in it's killing
effect on fungal spores. Remember, the deserts of California contain
many species of very, very, very old fungal spores, despite all the
solar radiation.
Moral of this story - fungi are on and in everything. Good hygiene for
your camera and lens should keep them from taking over!! What is good
hygiene you say? Well, I got a used and broken 30 gallon aquarium (free
from pet store), used a butyl caulk to seal the broken glass, placed a
small dehumidifier ($10) in it and a all spectrum aquarium fluorescent
light on top (called a Vitalight in the aquarium trade). I turn it on
for about 2 hours each week and have not had anymore problems in over 5
years.
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Gary Reese
Las Vegas, NV
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