When collecting old lenses, one is bound to come across lens fungus at some point. It might sound a bit odd, but fungal spores can grow behind glass elements, feeding on trapped organic matter and oils. At best, the colonies remain small, become inert and produce no visible photographic effect. At worst, the acidic byproducts of some rare species of fungus will actually eat away at the glass itself and cause irreparable damage. Given that we’re surrounded by tiny spores anyway, it’s no surprise that some lenses have a fungus problem !
So, what can one do about the problem? Most people will avoid buying fungus infested lenses (I do in most cases), but if you’re intrepid and think you might be able to buy a bargain (or have been burnt by a dodgy ebay seller), then you might want to consider trying your hand at cleaning it up. With that in mind, here’s a photo of some of my humble lens and camera repair toolset:
Some tools are not pictured, but the basics include the usual suspects, including pliers, utility knives, nailclippers, White Lithium Grease (great for regreasing stiff focussing helicals and other moving parts), WD-40 (not recommended by many, but useful on non-critical areas to loosen up stuck parts), Acetone (for wiping off nail-polish that is sometimes found sealing tiny screws), jewellers screwdrivers (essential for those tiny screws), spanning wrench (for unscrewing lens retaining rings), Kimwipes (lint free tissues), Q-tips (great for delicate cleaning), makeup removal pads (great for cleaning camera bodies), Isopropyl Alcohol (great for cleaning dirt and grime away on those camera bodies and lens barrels), B+W Lens Cleaner fluid (for cleaning lens glass), and Hydrogen Peroxide.
I bought a Kowa Super Prominar 50mm f1.3 projection lens very cheaply because it had fungus behind the front glass element. You can see the nasty fungus in the top image below forming a haze near the perimeter of the lens.
After removing the front lens retaining ring with the spanning wrench and removing the lens element carefully, I was left with these component parts:
It’s wise to lay the removed parts of any lens out in the order in which they have been removed so that it is easier to put them back together in order. The front element in this lens is held in by one retaining ring. After cleaning each of the metal parts individually with isopropyl alchohol, I turned my attention to the glass lens itself. You can see the partially disassembled lens and the front glass element below:
I tried rubbing away the fungus with isopropyl alchol first, but the toughest residue didn’t budge at all. I then tried acetone, but that also failed. Scratching my head, I carefully used a Q-tip and some hydrogen peroxide. This method worked a charm, and cleared away the remaining fungal residue. Luckily no acidic glass etching had taken place, and the glass was clear beneath the fungal colony.
After making sure there was no residue left, I cleaned the entire element with isopropyl alchol again, used some B + W lens cleaner to get it squeaky clean, and finally used a Giotto rocket blower to blow off any remaining dust and lint. I replaced the glass in the lens barrel and then replaced each piece in backwards order to complete the lens assembly.
As you can see in the photos above, the lens is now completely clean and usable ! She’s a beauty ain’t she?