When studying intensely for my college entrance exam, I decided to put my telescope away in the closet so that it would not be a distraction. One year later, after passing the exam, I was a little shocked to find it full of fungus.
I knew that I was supposed to keep my telescope in a well-ventilated area, but I was surprised at how fast the fungus grew in just a year. In Japan, it’s very humid in summer, which is bad for optical devices.
When you find fungus on the lenses of your binoculars, it can be very difficult to get rid of by yourself. In many cases, you‘d need to contact customer service of the maker and ask them to replace the entire optical unit. This can cost more than buying a new pair.
Since then, I have been careful not to let this happen again. As long as you store your binoculars properly, you can use them throughout your life.
In this post, I will show you how to protect your binoculars from fungal growth and how to clean the lenses.
How to store your binoculars properly
You need to protect your binoculars from the fungal growth that can ruin the lenses. Fungi grow easily in places with high humidity and little ventilation.
There are two ways to prevent fungal growth. If you often use your binoculars, you can just hang them in a well-ventilated room. They will stay even more ventilated if they are stored outside of their case.
The second way to store your binoculars is in a dry box that can be sealed.
These usually have a humidity indicator that you can check. You can adjust the humidity by using a drying agent (desiccant).
If you think this is too much trouble just to keep one pair, you can put them in a Ziploc bag with a drying agent. Just be sure to replace the drying agent with a new one every few months.
It’s also important to avoid high temperatures. Some people keep theirs in their car, where it can get over 60 degrees in summer. This is a sure way to damage your binoculars.
For example, the O-rings and oil that work to keep your binoculars air-tight can fail. High temperatures also can turn the rubber on the body and eyecups into a sticky mess.
It should go without saying that you should clean your binoculars before putting them in a dry box as dirt or oil from your skin can be nutrition for fungi. Next, I will show you how to properly clean your binoculars.
How to clean your binoculars
First, I should tell you what NOT to do.
Wiping the lenses with a handkerchief, sleeve, or Kleenex can damage the coatings and the glass. These cause fine scratches on the surface of the lens, which degrades the image.
Also, you shouldn’t breathe on the lenses because saliva can also be harmful to the coatings. I used to watch my grandfather breathe on his camera lens, and then wipe it with his sleeve. This is a bad combination!
Remove all the dust first!
Before beginning to clean your binoculars, wash your hands with soap to avoid fingerprints on the lenses. If oil from your skin is left on the lenses for a long time, it can melt the lens coatings.
What you should do first is get the dust off. The lenses can get scratched if you don’t remove all the dust because dust includes minute sand particles.
The best way to get dust off of lenses is to use a blower designed for optical instruments.
You can use canned air cleaners that are often used for computers instead of a blower brush.
However, you need to be careful not to get the nozzle close to the lens, as they contain additives that can be harmful to the lens coatings. You may have seen the white coolant that comes out of canned air. If this sticks to hot glass, it can actually crack the lens!
Clean the lenses with ethyl alcohol and cotton swabs.
Ethyl alcohol, which can be bought at most pharmacies, is very useful for cleaning lenses. Try to find 100% pure alcohol (ethanol). This is not the same one used for sterilization (rubbing alcohol). Cotton swabs are also useful for cleaning lenses.
After making sure there is no dust on the lens, dip the tip of a cotton swab with a little ethanol and rub the stained areas including fingerprints very gently. Then, gently wipe the area with a new cotton swab (without alcohol).
It’s important to do this rubbing gently as the lens surfaces are easily damaged. Rub as little and as lightly as possible.
I make it a habit to cover the lenses with the caps when I‘m not using my binoculars. When you hang your pair from your neck, even talking can inadvertently spray the ocular lenses with saliva.
This lens should be cleaned off immediately. The sooner these droplets are cleaned, the easier they’ll be to get rid of.
This may sound paradoxical; but it is important to clean the lenses as infrequently as possible.
I highly recommend binoculars with water-repellant coatings because you don’t have to clean the lenses as often as those with regular coatings.
How to clean the exterior of your binoculars
The dirtiest part of your binoculars is usually the exterior body. Dust and dirt can accumulate in the creases and crevices which can be blown off with compressed air. Don’t forget to cover the lenses with the lens caps.
Use a clean, slightly damp cloth to wipe down most of the body and a cotton swab for difficult-to-reach areas. I do not recommend using alcohol on the rubber areas. It‘s okay to clean the body frequently.
As you may know, prevention is a better strategy than frequent cleaning. Just using the caps can effectively protect your binoculars from dust and dirt.
However, you shouldn’t need to be so careful that you can’t take your binoculars on outings. You got them to use, not to sit on a shelf.
Letting fungi grow on the lenses should be avoided. It is, therefore, important to store your binoculars properly.
Frequent users can store their binoculars by hanging them in a well-ventilated room without a case. But the best way to store them is in a dry box with a humidity indicator.
When you need to clean the lenses, first get rid of the dust with a blower brush. Handkerchiefs and other abrasive materials can scratch the coatings and the glass.
With a little ethyl alcohol and cotton swabs, rub the surface of the lens very gently. It is important to minimize lens cleaning. The more frequently the lenses are rubbed, the more chances they have to get scratched.
You can use a clean cloth to wipe down the body and cotton swabs for difficult-to-reach areas.
I suggest that you use lens caps as often as possible to prevent your binoculars from dust and dirt.
With a little care, your binoculars can last you a lifetime. Now that you’ve learned how to clean your binoculars, you can feel free to bring them on your next outing.