Waterproof Binoculars – Keep Moisture Out

Fog and waterproof binoculars are perfect for anyone who has to deal with really bad weather, extreme temperature fluctuations, and high humidity environments such as the jungle or on the ocean. Waterproof binoculars work in any kind of weather and environment because the seal protects them also against dirt, dust, and sand.

These are essential properties that actually every outdoorsman or prepper wants in a good pair of binoculars. But especially when hiking in harsh environments, it is important that binoculars are waterproof. Seafarers and sailors who are exposed to bad weather and humidity also need binoculars that are waterproof and fog proof.

Why Waterproof Binoculars Are Better

heavily fogged binocular lens
Heavily fogged binocular lens

Not ending up with moisture in binoculars is critical so that the binos do not fog up on the inside. This could happen during extreme temperature fluctuations, the condensation film that then forms with the finest water droplets on the lenses would impair vision.

Regular binoculars that are not waterproof and fog proof are not airtight. So there is air exchange between the outside and the inside of the binoculars and humidity that is part of the air all around us may enter the binoculars.

When going from a cold environment to a warm place, you will notice water condensation on the binoculars. That happens outside as well as inside the binoculars.  Moisture inside binoculars will cause mold to grow and damage the optical parts.

So waterproof binoculars have no doubt a number of advantages that allow you to go birdwatching, go hiking, hunting, fishing, or yachting on the ocean without having to worry about the weather damaging your binoculars.

How to prevent moisture in binoculars?

First of all, it needs a precisely manufactured, high-quality housing that offers protection and stable permanent placement of the optical parts. The chassis of better binoculars has often some sort of rubber armor to protect the instrument from shocks and blows when use gets tough. Some models may have protective coatings in eye-catching colors, such as orange or yellow, so they are easy to spot in dull light conditions.

Although a rubber coating protects against mechanical shocks and occasional drops of water, the rubber coating alone is no guarantee that no water or moisture will get into the binoculars.

O-ring seals prevent internal fogging

A watertight and airtight seal to prevent moisture from entering the inside of the binoculars is achieved through the use of rubber O-rings. In addition, the binoculars sealed in this way are often filled with a noble gas.

Gas-filled binoculars are airtight and waterproof, so there is no exchange of air with the outside, and moisture cannot get in either, so they are waterproof and fog proof. Even if they fall into the water, no water gets in and they stay dry inside. When there is no moisture in binoculars, the interior surfaces can not fog up when going through rapid temperature fluctuations.

Why are binoculars filled with gas?

Glass fungus on binoculars
Damaged due to glass fungus

In order to protect the optical systems and mechanical parts of a high-quality pair of binoculars from fogging, growing lens fungus, and internal corrosion due to the building up of moisture, they are filled with an inert gas.

Binoculars are filled with gas with a slight positive pressure to prevent anything from being able to enter them. Moisture can not build up through condensation when taking the glass from cold to warm or exposing it to other temperature fluctuations.

Some binoculars have small valves that allow them to control the internal pressure of the binoculars and to renew the gas filling if required.  Gas-filled binoculars guarantee perfect viewing in every situation.

What gas is used to fill binoculars?

The gases used are either Nitrogen (N) or Argon (Ar).  Both gases are inert and do not react with any of the materials used to manufacture binoculars.

Some manufacturers prefer the use of Argon instead of Nitrogen to fill the interior of high-quality binoculars. Argon is a noble gas of superior value. It has a higher atomic weight and the atoms are larger.

The advantage of Argon gas-filled binoculars over a Nitrogen filling is that the larger Argon atoms take much longer to disappear from the binoculars. This is because no matter how accurately something is manufactured, no material and nothing is absolutely gas-tight. And as the law of Diffusion requires everything wants to be in equilibrium.

This means that over time the gas from inside the binoculars, where the argon or nitrogen concentration is very high compared to the concentration outside the binoculars, will diffuse outwards until a balanced concentration is reached.

Are gas-filled binoculars worth it?

The advantage of an additional inert gas filling in binoculars that are waterproof anyway compared to binoculars that are “only” sealed waterproof is debatable.

Both are waterproof and fog proof, whether it is just filled with air or with a noble gas, a waterproof seal is to stop moisture from entering and prevents binoculars’ internal fogging, thus preventing mold and fungus to grow on the glass surfaces.

Environmentally sealed binoculars are more reliable and always perform as they should. This is especially true when using binoculars in tough weather, out on the ocean, or when there is a likelihood of thermal shock from extreme temperature fluctuations.

An advantage that could be seen, in gas-filled binoculars, would be the reduced susceptibility to corrosion of internal mechanical components and lubricants due to the absence of corrosive oxygen.