Originally posted by Teja Thanks for all the support & advice everyone. After the initial panic subsided I re-evaluated the damage. The bad news is that, several more lenses had the same filament like growth (I am not sure if it really is fungus). The good news is that most of it was on the outer surface of the lens elements and cleaned out nicely with not too much effort. Only two lens (Sigma 24-135 and Pentax 35-70) are showing some infection on the inner sides. These have been exposed to the strong sun here for over 48 hours and hopefully that halted any further growth.
The Pentax 35-70 is easy to open, I did it once before to blow out some dust that got inside. So I will open it this weekend to clean out that inner lens surface. I will take pics and post them in case any one here is interested. The Sigma 24-135 is a relatively newer lens and I am not going to try & open it. If the fungus or whatever stops growing and doesn't show up in the photos then I will leave it as it is.
Teja, I have cleaned several lenses off fungus, though storage in my environment is much easier, as it is by far not as hot and humid as it is in Southern India:
– exposing the lenses to direct sun light is a good idea. Remove the back lens cap too and wrap aluminium foil around the rear of the lens. This serves two purposes. Firstly it prevents to lens from burning anything beneath (Table, clothes etc.), secondly it reflects the sunlight back into the lens, improving the UV action.
- killing the fungus will obviously not clean the lens. If you have serious fungus inside the lens (the filamants you metioned sound very much like fungus growth), you need to take apart the lens and clean. If you do so, use alcohol also to clean out the mechanics.
- you could expose the lens to formaldehyde (sold as Formalin fluid) for a couple of days in a closed storage jar or whatever. Just be very careful, as formaldehyd is quite unhealthy. The advantage is, that the gas will penetrate the lens and kill everything inside, even in those spots, you are not able to reach mechanically for cleaning. Place the lens inside the container in a way, that it doesn't get into contact with the Formalin itself.
Make a formaldehyde test with a less valuable lens, as I don't know, whether it might interact with some of the plastics inside the lens.
For storage: make sure, that you don't use completely closed containers, unless you use some means of drying. I would opt for a unheated dryer anytime, as some of the lubricants in the lens become more viscous when very warm and will creep in all the unwanted places, like the diaphragm. I am not a fan of air conditioning, as it is an enormous waste of energy, but in such a case a room with air conditioning might be ideal. Just be aware, that an air conditioning system is a very good place for fungus growth itself, if there is no regular maintenance.
Ben