How to remove fungus from lenses using soap, water and vinegar

Fungus isn’t an issue most of us have to deal with when using modern glass. It comes pretty well sealed, and it’s usually not old enough to let major fungus issues develop yet. But, if you’re buying older lenses at the rate Mathieu Stern does, it becomes inevitable. Usually, you’ve got a couple of options. The first is to simply sell it on and find another. But the more productive route is to just give it a good clean.

In this video, Mathieu shows us how to open it up and get to those elements. Then, an easy way to get them clean using soap and water, then vinegar. Finally, how to reassemble things so that everything works as intended.

As you can see, it’s fairly straightforward. Some lenses are going to be more difficult to open than others. You may have to go in through the body end of the lens to get to the element you need, but the technique is basically the same.

But, there is one key tool you’re going to want to get before you attempt something like this. And that’s a lens wrench. These are essentially an adjustable wrench which have pointed tips on one end, and flat tips on the other. This is because some lenses have a pair of holes to loosen and tighten things, while others have ridges into which the flat tips will fit.

You can see that the lens Mathieu uses here has a pair of holes. So, it’s time for the pointy tips.

With the front ring removed, the lens element simply falls out. Mathieu’s technique here for safely removing the element is a lot like removing a Christmas Pudding from its bowl. He places a notepad on top of the lens, and turns the whole thing over at once, using the pad to catch the element. Shining a light from behind shows just how obvious the fungus is.

Carefully, you’ll want to transition over to the sink, and pour hot water over the lens. Dish washing liquid soap will also help to kill mould, bacteria and fungus on the lens, as well as make existing fungus come off the glass more easily. You don’t need any special cloth or materials to do this. Simply rubbing it between your hands under the hot water will clean it off.

Pressing it inside a good quality paper towel that isn’t going to fall apart will blot it dry. Then you can pour a little white vinegar over the lens to help prevent water spots from forming on the lens. Vinegar is also said to be a rather effective anti-fungal, helping to prevent it from returning. Once it’s completely covered, just dry it off again with a fresh piece of paper towel.

For reassembly, you’ll want some clean gloves. Latex, vinyl, or white cotton gloves should work well. Basically, it’s to prevent grease and fingerprints from getting onto the glass you’ve just cleaned.

Then loosely screw the retaining ring back on by hand and tighten with the lens wrench. And you’re all done.

Newer, and more complex lenses might require a little more advanced surgery. If the fungus is on elements further into the lens, you might need to dismantle it completely, but the cleaning process is the same.

If you do have to take a lens completely apart, I’d suggest shooting video or taking photographs as you dismantle it. That way, you can look at the steps in reverse to remember how to reassemble it.

How do you clean your lenses?