Fungus

I went to buy a filter at Mathers of Lancahire yesterday, and one of the salesmen ver generously gave me, free of charge, an smc Pentax-M 75-150mm f4 lens, which is in great condition apart from two spots of what I assume are fungus, both on the front of the front element. The worse one is shown here (apologies for the hand-held macro shot!):




It seems like a really nice lens, so I would love to fix it. I have read all sorts of ideas, from using aceetone, meths and even one suggestion of petrol! Does anyone know how I could clean this lens, or do I need to take it to a specialist? It appears to be just on the surface of the lens. Also, is it likely to contanimate any of my other lenses?

Whoops! Should probably have been in the Troubleshooter section if a mod wants to move it.....

It depends whether or not you can easily dismantle it. I have succesfully cleaned a Takumar 135mm f3.5 that was riddled with it and it is now spotless. As for whether or not it will grow back or contaminate your other lenses, the answer is 'no' as long is it and your other lenses are not stored in conditions which favour fungal growth. Fungal spores are everywhere and will already be in your other equipment; if they have not grown into fungus so far, chances are they won't.

Good luck!

PS forgot to say, I use Isopropyl alcohol. Anything that won't damage the lens coating will do as long as the fungus has not etched into the coating.

I have used vinegar or computer monitor cleaning spray (alcohol-based) in the past, none of the lenses I have thus treated show any signs of a return of the fungus. I tend to dunk a cotton bud in the liquid then polish the fungus away.

Surgical-type gloves help to keep fingerprints off the elements while cleaning and reinstalling them - you can buy big boxes of these and they have numerous uses around the house (refilling grease guns, unblocking sinks, any unpleasant jobs really!)

SMC coatings seem to stand up to fungus pretty well, I know I have a 50mm which was absolutely riddled with it but cleaned up perfectly aside from slightly more dust than my untouched minty example of the same lens.

Ponds Cold Cream and lighter fuel.
See theses pages.

link

link

It might be worth noting that "cold cream" is made from the following ingredients (or variations of very similar compounds)

Paraffin Wax (Candle wax)
Beeswax
Liquid Paraffin
Borax
A soft smell- such as rose water.

I used to make it by the bucket full and package it in margarine tubs for any girls that wanted it. Then liquid paraffin and borax became politically unpopular.

Make of that what yoou will, but I would suggest the Liquid Paraffin/Borax is the active fungal remover, simply because its a gentle cleaner. I'm not a biologist but I doubt if any have antifungal properties

regards
Bernard