Is there a quality anti-fogging product for windows?

White95Max said:
Nope. Let's take 1kg of air at 15*C for example. It has the ABILITY to hold 11g of water vapor. At saturation, it holds 11g. Let's say at a particular time it's holding 8g of water vapor. That means the relative humidity is 8g / 11g = 72.7%.

As you heat the air, the water vapor is not changing. If you were to heat the same 1kg of air to 20*C, it has the ABILITY to hold 15g. It is still only holding 8g of water vapor though. So now you have a relative humidity of 8g / 15g = 53.3%.



Think of the morning fog. You see fog in the morning because the temperature has dropped overnight, and unless a cold front has moved through, the water vapor content of the air is likely to be the same as it was the evening before. The air cools, the relative humidity increases, and fog forms as the air reaches saturation (100% relative humidity). As the morning sun heats the air and the earth's surface, the fog begins to lift. As the air near the ground heats up, the relative humidity becomes less than 100%, and the fog dissipates.
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Thanks Paul for that explanation, it does make sense in that aspect.



I can not directly relate this with the original topic though, I just can't picture it.



Reason being is that because no matter how much the air is heated inside of a car, if the A/C is off and the humidity is high, there will be fogged windows. Now maybe the comfort level does not allow me to have it that hot inside haha. Also there is a definite feeling of "clamminess" or "moistness" (if you would) when the heater is on w/o A/C. The A/C removes humidity from the air which keeps the windows clear.



Do you agree with that?
 
Man.......this thread is making my brain hurt! (lol) Paul: I'm very impressed with your scientific knowledge. Very nice!



However, I used to use shaving cream on the inside of the shield of my hockey helmets. Took care of the fogging. (lol)



Why am I picturing someone rubbing barbasol all over their windshield.........
 
twitch said:
Now maybe the comfort level does not allow me to have it that hot inside haha. Also there is a definite feeling of "clamminess" or "moistness" (if you would) when the heater is on w/o A/C. The A/C removes humidity from the air which keeps the windows clear.



Do you agree with that?
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Yes, the A/C lowers the humidity of the air. I think the feeling of "moistness" is just because you're beginning to sweat after having the heater on for a few minutes. The humidity in your area is probably always pretty high, so it doesn't take much heat to bring the heat index to an uncomfortable level. The higher the humidity, the longer it takes for perspiration to evaporate from your skin. This is what cools your body, and if it can't cool, it will continue to perspire in an attempt to cool itself. So moisture builds up on your skin and you feel uncomfortable.



Reason being is that because no matter how much the air is heated inside of a car, if the A/C is off and the humidity is high, there will be fogged windows.
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Nope. The air can only get to 100% humidity (actually it can be "supersaturated" >100% but we won't get into that :) ), so the instant you begin heating the air, its humidity will decrease.

Additionally, the dew point (measure of humidity) can only get so high. You won't see a dew point of 100*F, so obviously if you heated the air to 100*F there's no way you would have fogged windows. Watch the weather and pay attention to the dew point. The temperature has to fall to that level in order to create fog.

The A/C compressor/condensor works to actively REMOVE water vapor from the air. The heater just decreases the relative concentration of water vapor in the air. Either way, it is drier air, so it will feel more comfortable, as your body will be able to quickly evaporate water from itself if cooling is necessary.
 
I agree with everyone that Rain-X is an inferior product. I tried it in the past.



I have tried shaving cream also but that leaves a hazy film.



The Fog clear gel by Glass Science is another inferior product. Also leaves a haze. Returned it to Kragen after the fact



The best product is sadly discontinued. It was made by the "No Touch" brand company before they were bought out by Permatex. They had a spray on Anti-fog that smelled like oranges. It was easy to apply and left no visable film. Why they discontinued it, I wish I knew.



I saw a recipe during a google search for using a 1:5 to 1:10 ratio of Johnsons Baby Shampoo/H2O but have not tried it yet.



My search continues...
 
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