Dirtbike Tech:

All Fogged Up?

The Fogged Goggle Fix

By Rick "Super Hunky" Sieman

August 2001 -- The idea for this valuable tech article came via Off-Road.Com ex-staffer, Andi Vogt. We've dug this one up from the ORC archives of many years ago to reintroduce it into some era other than the dinasaur age.

Anyhow, Andi received the following email and passed it on Rick's way:

The Spark

"My brother bought a new anti-fog helmet this winter. While out riding, though, it fogs up to the point that he can not see. What are the standards that must be met to sell merchandise as anti-fogging? Any ideas where I might be able to research this further? I saw one of your articles said to look for a helmet that is rated by ANSI or SNELL. Can I find that somewhere on the Web? Or a similar source for ratings of "ANTI-FOG"?? Any help would be appreciated, or just point me in the right direction.

THANKS!
Paula

P.S. The store that sold the helmet ($100) is not being helpful.

First off, there is no such thing as an anti-fog helmet. There are, however, anti-fog face shields that are attached to helmets.

While there are, indeed, standards for helmets, there are NO STANDARDS for anti-fogging shields or goggles.

Since I not only ride and race (both dirt bikes and off-road trucks), this is a problem that I’ve had to deal with over the years. Compounding the problem is the fact that I wear glasses. This means that I not only have to deal with goggles fogging up, I also have to deal with the two layers (inner and outer) of the glasses fogging up, as well.

In the process of riding half-blind at times, I’ve found out what works and what doesn’t work. So let’s share some of this with you.

Why Things Fog Up

All face shields or goggles are made out of some kind of plastic, or glass. They are invariably made out of transparent stuff. Early attempts with plywood goggles were dismal failures.

All fogging of goggles and face shields is caused by a difference in temperature and humidity.. If you just took a pair goggles and put it on a crash test dummy, the goggles would not fog up, no matter what the outside temperature was.

However, when those same goggles are attached to a human being, that’s when the problems start. Let’s say the outside temperature is 60 degrees. The normal temperature of a live person is 98.6 degrees, which gives you a huge near-40 degree differential.

So, you have the ideal conditions to create a mist of moisture, or fog .

But what happens when the outside temperature and your body temperature are about the same? We’ve all had goggles fog up on a 100 degree day, very close to normal body temperature. So why do goggles fog up then?

Simple. Because an area of the face is covered up with goggles, it raises the skin temperature up considerably, causing sweat to form on the skin, which then evaporates into the air, which in turn gets transferred to in the inside of the goggle lens. Instant fog.

An easy demonstration of how moist air turns into fog can be accomplished by breathing heavily on a glass surface, such as a mirror.

Or just take a real hot shower in a bathroom on a cool morning, and notice how quickly the mirrors fog up. Take that same shower on a hot day with the windows open, and very little fog will be seen on the mirrors.

Moving Air

Here’s a simple test on the effect of air on fogged surfaces. Take a hand mirror and breathe heavily on the glass until it fogs up. Let it sit for a while, and in a few minutes, the fog will go away.

Now, fog up the mirror again, then wave the mirror around like crazy. In seconds, the fog will disappear.

This is why face shields and goggles usually don’t fog up while your bike (or truck, or buggy, or ATV) is moving.

Trade-offs

OK, we know that moving air will reduce, or eliminate, goggle fogging. This means that some air must be allowed to get between the covered portion of your face and the inner surface of the goggles.

The more air you let flow in, the less fogging potential.

However, the trade-off is allowing dust to get into your eyes. If the goggles seal tightly, fogging is a problem. If you have some air vent gaps, you can get all kinds of grit and dust in your eyes.

Whenever I used to race a muddy event like the Blackwater 100, I used to tear all the foam out of the frame of the goggles I was wearing for maximum air flow. This gave me reasonable eye-protection and completely eliminated goggle fogging.

One Blackwater 100 race, however, had a combination of swampy terrain and some dusty fire roads, and my eyeballs got sanded-out badly in the dry stuff. Bad move on my part.

The next year, I made sure that the goggles I used had thin foam on the frame, and I sprayed the foam with Endust to catch the airborne grit. This worked well, but since I crashed my brains out in a bottomless bog, it was after all, a clever exercise in futility.

So, with this in mind, if you do not coat your goggles (or face shield) with some sort of anti-fog solution, maximum air flow is a must!

Home Grown Fog Eliminators

In the early days of off-road racing, we didn’t have much in the way of anti-fog chemicals and solutions, so we made do with what was at hand. And here’s what worked way back then:

1. Soap.

Before a race, I used to take an ordinary bar of hand soap and soak in for a few minutes in water to soften it up. Then I would scrape some of the softened soap off and make a thin paste of it with more water. This would then be applied to the inner surface of the goggles, and allowed to dry for a few minutes. When dry, I would buff the lens with toilet paper repeatedly until the lens were clear. This worked great and would give you several hours of decent anti-fogging protection.

2. Liquid Soap.

It worked as well as regular soap, but since I usually forgot to bring any liquid soap with me, I usually resorted to regular old bar soap.

3. Potato.

Yep, you can take a regular potato and anti-fog your goggles with it. Simply cut a wedge of the potato and rub the white part on the lens. Let the solution air dry, then buff it clean, just like the soap trick.

4. Apple.

You can use an apple (or pear) to do the same trick, but it’s not as effective.

5.Car Wax.

While some riders used car wax to coat the inner lens as an anti-fogger, I felt that it took way too much work to buff the wax out enough to remove the hazed glare it left on the lens.

6. Spit.

Skin divers have been doing this for years, but the effect is relatively short.

There are a number of commercial things you can buy to stop fogging, that have nothing to do with racing. Among them are:

Bathroom Cleaners.

There are many bathroom cleaners that work well as anti-fogging agents, but many of them have harsh chemicals in them that can cause your eyes to burn.

Windex.

This does a decent job, and some riders swear by it, but I recommend that you do not use the ammoniated type.

Dow, Ajax and several other companies make a mirror cleaner/defogger that works well, but again the evaporating vapors can hurt your eyes, and I’ve found that their effectiveness is limited to about 45 minutes or so.

Plastic Cleaners.

You can find a huge selection of glass and plastic cleaners at most auto parts stores (Chief, Pep Boys, etc.) that work reasonably well as anti-fogging agents. They have the added benefit - in some cases - of reducing scratches and extending lens life.

Furniture Polish.

Pledge and many other brands of spray polish can be used to reduce fogging. Some leave a hazy coating on the lens, and some don’t. Experiment to see what works for you.

Specialty Stuff

Various goggle makers sell anti-fogging solutions and cloths to work with their product, and some of them toss in that product when you buy the goggles. Some of the best are Smith, Scott and Bell anti-fog.

For my own goggles, I’ve come to rely on the Smith No-Fog Cloth. Here’s how I use it:

1. Make sure the lens is clean and dust free.

2. Breathe lightly on the lens, or moisten the lens with a piece of damp toilet tissue.

3. Wipe the lens surface with the No-Fog Cloth until it’s dry.

4. Breathe heavily on the lens again.

5. Repeat the cloth rubbing.

6. Buff any remaining haze off the lens with a soft towel, or toilet tissue.

Under normal conditions, I find that this will give you about a half-day of fog-free riding.

Options

For really cold days of riding, I don’t rely just on the No-Fog Cloth. If you get to one of those situations where you have to push your bike over an obstacle, or pick it up after a crash, you might experience some fogging, no matter what you use.

For those days, I use a Smith double Lexan lens. This operates on the same principal as double-glass windows. These lenses not only have two layers of Lexan, but also have vent holes in the top edge with foam covering the holes to keep dust out.

The outer lens takes the cold hit of air and the inner lens is much closer to your face temperature. With these lenses AND an anti-fogging solution, you’ve got the best possible combination.

For hot weather riding, I use Smith Turbo goggles. These little beauties have a small fan built into the frame of the goggles, that you can turn on or off. While you’re moving, you can turn them off, as the normal air flow prevents fogging.

When you’re going slow, or stopped for some reason, or horsing your bike over a fallen log, flick the fan on and the cooling air prevents fogging and perspiration from forming on your covered face area.

My Turbos are older one-speed models, but Smith now makes a two-speed version, with a low and high switch. You can get about 50 hours of actual use with the switch in the low-speed position, and maybe 10 to 15 hours out the faster mode. All this from a tiny nine-volt battery.

The only drawback is that you can feel the slight extra weight of the fan and the battery on the bridge of your nose, but it’s certainly not objectionable. You’re just aware of it.

For the absolute ultimate in anti-fogging, consider using a Turbo goggle with the double-layer vented Lexan lens, and anti-fogging solution on the lens.

If you’re wearing a basic goggle and use anti-fogging solutions, consider some of these helpful tips:

Wear one of those sweat-absorbing head bands to prevent perspiration from increasing the fogging possibilities.

If you’re wearing glasses, put a small absorbent pad on the bridge of your nose. This is where perspiration is heavy, and the heat from your face can actually cause beads of water to form on the inner surface of your glasses. I use small pieces of Dr. Scholls foot pads cut to fit over the sizeable bridge of my nose. This has a secondary benefit of keeping you from cutting into the bridge of your nose with your glasses if you should take one of those ass-over-heels crashes and dig your helmet into the ground. Trust me on this one, as I crash a lot, and with great enthusiasm.

If you’re using a full coverage helmet with a face shield that fogs up, glue some foam strips to the lower and side edges of the shield, where it sits against the helmet opening. This will allow some decent air flow and stop all fogging as long as you’re moving.

In warm weather, use a vented helmet to prevent heat build-up in the helmet itself, which leads to perspiration on your face, which in turn, contributes to fogging.

There are some lenses and face shields that claim to have been pre-treated with an anti-fog solution. In my opinion, none of them live up to their claims … at least the ones I’ve tried so far.

Flip-up shields. For those who ride street and use full-face helmets with face shields, get a hinged shield that can be flipped-up easily. This way, when you experience fogging, say at a stop light, you can just flick the shield up, and get some air on the inner surface.

Breathe down. If you’re using a full face shield and exhaling through your mouth, extend your upper lip out a bit and breathe down, rather than straight out at the shield. Hey, this really helps!

In really cold weather, wear a bandana over your mouth. This keeps you from breathing your hot air directly onto the face shield and dramatically reduces fogging.

What Doen't Work

Don’t use Rain-X as an anti-fogger. While this stuff works great on the outer surface of your goggles to help with rain and splattering mud, it doesn’t help on the inner lens.

Anything with ammonia or harsh chemicals in the solution is a no-no. Even if you let it air dry, moisture from your face can re-activate the chemical and cause it to irritate or cause a burning sensation in your eyes.

Don’t use any soaps with grit in them, like Lava, as applying the soap will scratch the lens.

Don’t rub the lens too much when applying the anti-fog solution, as excess rubbing can cause static electricity to build up on the lens, which will attract dust and cause it to stick to the inner lens.