Last night here in Portland it was moderately cold and very foggy after nightfall. I noticed that when I went out to my car my winshield had a good layer of condensation on it on the outside which obscured vision from the inside. All the windows all the way around in fact were nicely coated. I looked around at all the other cars (all modern, less than ten years old probably), and almost none of them had the same build up of water on them. Many of them were quite clear of any build-up at all.

So... I was just wondering to myself as I drove off and used my wiper blades as well as waited for the inside defrost to clear things up.... what is it with the composition of more modern glass that prevents the same ammount of build up of water on them? Was some advance in glass chemistry made? Do they coat modern glass with some anti-fog compound now? If so... has anybody found some kind of spray-on stuff that will cut down or eliminate the pre-drive fog-up?

Dunno why they fog more but Rain-X is super stuff for rollin the moisture off.

Mike!

Every older car I've had has had this scenario. I think that the interior will always be just that much hotter than the exterior, especially if you drove it in the last 12 hours. If you're getting rid of ice on the outside use a scraper with warm, not boiling water; I saw a guy crack his windscreen last winter. Boy did he curse!

I always have a cloth handy to wipe down every window before I start off. I had a look at some websites and it seems that lemon juice, vinegar, potatoes, cigarettes and ...hhrrrrmmmm ... something else, will all help with misting up windows. Choose as you see fit.

Yah, I kind of hoped that my days of manual wiping were over when I made the transition to volvos from VW's. I guess I will have to keep a cloth handy for those extra-foggy times when I'll need an outside wipe down. Here in Oregon, if I tried to put anything on the outside windows, it would just wash off in the rain every five days or so. At least the problem is not significant inside, and the heat actually WORKS, like it never quite did in my old busses!

The other thing not mentioned is that most modern cars automatically turn on the A/C when the defroster is switched on engaging the "dehumidifier" canister and reducing inside fog much faster.
You may just need to clean all the contacts on your fan, etc. and ensure your old swede is putting out as much heat as possible to help dry up the inside.
Checking your floor mats for water saturation as previously suggested will also make a huge difference, You want it as dry as possible.
That defog stuff from rainx makes the moisture bead up and drop off the window so you can see out. Great for vision, but then you have drips everywhere around the car, tried it once in the wagon, good idea turned into a big mess. :).
-Erik

Thanks Erik,

But I was actually talking about the outside of the windshield, and all the outside of the windows also for that matter. My intererior is pretty dry, so no worries there... thanks though.

I have noticed that older cars seem to have more of a problem. Wonder if it is from micropitting on the glass providing surface points for condensation to form???

Well... that's a very interesting theory. You might have something there.

A thing you might want to check since your car seems to be the only one in the area that is fogged up on the inside.... Lift your mats and make sure they are not wet. It sounds like you might have a wet floor mat or hopefully not a leaking heater core which will give you a oiy film on the inside of the windshield. Another anti-for trick from the days of the old model "A" Fords was to use a damp cigar and rub it on the glass. Since this can be messy I woulden't suggest that but at your local auto parts look for Rainex brand, (the people that have the treatment that causes water to bead so you don't have to use your wipers unless it is pouring out)They make a anti-fog treatment for the insid of the glass on cars. Scuba divers spit on their face masks to keep them clear and I woulden't suggest that either.
Good luck,
Dennis

Dennis,

thanks, but I actually DID mean that the fog was on the outside of my windshield. It was much thicker than on any other car parked around me. When I get in, my breath starts to fog up the inside, but after five to ten minutes of driving and heater fan, this clears up very well. After a while of driving all's clear again and there's no problem at all. I just have a habit of making observations and then wondering why things occur like that.

Thanks for the input though.

He-he! This leads to revieling a really ancient good advise, normally only heard in the retirement-home:

Wipe your glass with a lemon cut in two! Wipe them off with cloth - No water!

How much is a lemon!?
--
/Soren

OK. Interesting idea Soren. I think that two halves of a real lemon sounds a little too messy and pulpy for me. I do have some lemon juice in a bottle however, so perhaps I will lightly diulute some, put it into a spray bottle and test this little bit of folk-wisdom on half of my windshield. I will let you know the comparison results some time soon!

it's not the composition of the glass, it's the thickness.

modern auto glass is much thinner (to save weight), therefore it conducts the temperature from the inside of the vehicle to the outside, and vice versa, quicker. This leads to less fogging and quicker clearing of the outside with heat from the inside.
--
'73 142, '75 242, '75 245, '80 245, '83 244, '86 244, '87 745T, 92 244 (for sale)

Hmmm, that's an interesting hyothesis, but I wouldn't think it quite explains why it does this while sitting for a long time? I would think that there's very little temp differential betweeen the inside and outside after it has been sitting for more than twelve hours, like it was last night when I went to go drive it. Night had fallen quite a while ago, so it couldn't have been some kind of greenhouse effect heating up the inside, then holding the heat until three hours after night-fall.

Anyway, you are correct that modern windows are much thinner. I heard this because that is one area where the manufacturers have attempted to save weight. This works quite well in fact, but the reverse side of that coin is that modern windsheilds crack and get holes from rocks much easier than old ones. I suppose the glass replacement companies don't complain about that particular trend...