Whether you are a recreational user or a professional, good binoculars are an important tool that you want to rely on. Modern quality binoculars are fairly sturdy and the few mechanical parts are usually maintenance-free. Still, a little binoculars care should be taken to reduce wear and tear to the instrument.
If you have your binoculars stowed away most of the year and only take it out for occasional observations you might not have to clean it much but still have to store it with care to avoid glass mold. Keep the lenses covered with the protective lens caps that most binoculars come with. Store the binoculars in it carry case or storage bag in a dry cabinet. Placing dehumidifier, like Silica Gel with it, will secure a dry environment.
Binoculars that are heavily used and are exposed to the weather and outdoor environment have to deal with a number of challenges that affect the functionality of even the best binoculars.
With a little care and the right kind of cleaning utensils, it is easy to remove the dirt grime from the instrument and extend the lifetime of your binoculars.
Removing minor debris
The Air blower and lens cleaner brush can be used to easily remove debris such as dust and small particles from the lenses. Be patient and avoid using too much force. You don’t want to scratch the optics with to much pressure. With a spray bottle, you can rinse debris off using distilled water or other special cleaning solutions. Be careful with non-waterproof binoculars.
To remove grease or fingerprints from your binoculars use Lens cleaning wipes and microfibre cloths. Be careful not to apply to much pressure and always clean lenses first with a lens cleaner brush the air blower. Small grains and debris particles could otherwise easily scratch the coating of the lenses.
Do not use dry paper wipes and strong solvents as they could attack and damage different materials, seals and coatings.
Best would be if lenses would not come in contact at all with crease and fingerprints as they can lead to long-term damage. Acids that from with moisture in the air could damage the lens coatings. Organic material in fingerprints could provide an environment for mold or fungi to grow. Unfortunately, dirt and debris cannot be completely avoided. So it should be promptly removed.
Rubber coating care
To remove the dirt and grime from your binoculars’ rubber coating, use a damp cloth or sponge and soap or dishwashing detergent. To maintain the rubber coating I use a silicon spray, which I carefully spray on a cloth and then wipe the coating with. Some people use talcum.
Fungi in binoculars is a big problem. It occurs usually during storage under wrong conditions.
Fungal spores are almost everywhere. Soon as spores find a suitable breeding ground, mold begins to grow. The fungus can be recognized by fine filaments growing on the lens surfaces. The waste products from the fungi are aggressive and will etch the lenses. Cleaning may remove the fungus, but not the damage left to the glass.
Nitrogen filled binoculars will not have much of an internal mold problem as their water and fog-proof feature provides a sufficient barrier. However, fungal growth may occur on the outer surfaces of the objective lenses when stored in a humid environment. Proper binoculars care and storage reduces the risk
Here is a very good detailed guide how to clean fungus from optics.