Cleaning Fungus: The Definitive Thread

[Ari]

I searched in a lot of places and came up with a few general answers, but I'd like to corral everyone's opinions on this into one thread.

What is the correct procedure for cleaning and removing fungus from a lens?

Microfiber cloth or lens cleaning wipe? Or something else?
Do you use any kind of liquid or application of heat/cold?
Are UV lamps effective? Direct sunlight?
Is any competent lens repair person able to do this, or do you know people who know their fungi?

Thanks

[LabRat]

The fungus itself is easily removed, but it is the damage under it that is the concern (and might be permanent) ...

Steve K

[Steven Tribe]

I have made comments before which I can't really add to.

- Mechanical removal is the way to go.
- I find the notion of using UV as a treatment rather silly. Is it supposed to "kill" the fungus and spores? It certain doesn't remove debris. Active spores will be present again after a few hours.
- Pre Jena glass (1890) and uncoated glass surfaces only get "wispy" fungus which is not attached to the surface and can easily be removed.
- Fluoride coated glass which has been etched by fungus is U/S.
- Don't confuse Devitrification and "ORganic looking" cement breakdown with fungus attack.

[Pfsor]

- Pre Jena glass (1890) and uncoated glass surfaces only get "wispy" fungus which is not attached to the surface and can easily be removed.
-

Lenses attacked by fungus in the pre-coated era were known to be a big problem in military optics in wet tropical conditions. Research in the best chemical removal means was spurred by this problematic.

[Tin Can]

Location and environment exacerbates/enhances fungus life.

I now try to obtain lenses from low humidity environments.

Use Silica packs and refresh them. Often.

I once found a huge silica pack inside a small safe of LF glass. No fungi.

Lenses attacked by fungus in the pre-coated era were known to be a big problem in military optics in wet tropical conditions. Research in the best chemical removal means was spurred by this problematic.

[CCHarrison]

hydrogen peroxide will remove fungus better than other chemicals.

[Ari]

hydrogen peroxide will remove fungus better than other chemicals.

Good tip!

[MBuchmeier]

I'm a microbiologist with more than 45 years of experience in the field, and a photographer. Over the years I have tried to "Save" a number of lenses with fungus from the scrap heap. The common factor that seems to provide the tipping point between success and failure is
whether of not the coatings and glass have been etched by the fungal growth. Fungi produce acids that are secreted by the mycelia, those filaments that hold the colony on the glass. Normally in Nature the substrate would be a mineral or an organic surface, and the acid releases nutrients that are needed for growth. A secondary factor is the degree of organic material in and on the glass surfaces which if not removed, will support a regrowth of the fungus. So based on these two factors you should be able to tell by inspection with an 8-10x magnifier after the fungus growth has been removed whether the glass has been etched and the damage is permanent. Factors that can influence this include the composition of the glass, the type of coatings, and the nature of the fungus. It goes without saying that it is important to clean the entire lens and shutter thoroughly in order to
remove any dirt.

[Pfsor]

... whether the glass has been etched and the damage is permanent. Factors that can influence this include the composition of the glass, the type of coatings, and the nature of the fungus.

And the time the fungus has been left to grow on the substrate. A newly infected lens can still be savable.

[MBuchmeier]

True, but that can be a factor of the type of fungus and the composition of the glass. A susceptible lens can be destroyed quickly by an aggressive species.
Tropical heat and humidity also promote rapid growth.