How to get better water behavior on back window?

[Desertnate]

My area has been in a bit of a drought over the last two years since I brought home my current car, so until recently I never noticed this problem:

When driving in light misty/showery/snow and rain mixture conditions, water just beads up on the back window of my BRZ and sits there. In heavy rains the factory conditioning of the glass works great and water rolls right off, however in lighter rain, the water gets really nice tight beads...and sits there making visibility difficult in some lighting conditions.

Does the angle of the glass and car design put me at mercy of gravity and aerodynamics, or is there something that will make the rear glass disperse water even better? My last coupe had a similar problem, but the aerodynamics would eventually lead to the glass being blown clear at speed. On that car I tried Aquapel and I also tried wiping down the glass with Ech2O. In both cases, neither product performed any better than the factory treatment of the glass. In fact, I couldn`t tell any difference. Some days I really miss having a hatchback with a rear wiper.

So...Is there some amazing product that will allow the water to roll off better than others?

[Setec Astronomy]

You`re the last guy I`d expect to be asking this. Are you saying this vehicle has some sort of special finish on the rear glass ("factory conditioning")?

You could be a prisoner of the aerodynamics. I`m not going to be much help, but RainX is a cheap try, I liked Opti-Glass the couple of times I used it before the sprayer clogged up, and I have some Diamondite that I found to be much easier to apply than RainX, but I stopped using it so I could use up my RainX. I don`t know how those compare to Aquapel, which I have never used. You could also try a wax (ok, I`m a heretic). What about your Mohs EVO? I told you I wasn`t going to be much help.

[Desertnate]

You`re the last guy I`d expect to be asking this. Are you saying this vehicle has some sort of special finish on the rear glass ("factory conditioning")?

I don`t know what you`d call it or what it is, but over time I`ve observed the factory/OEM glass on some cars have different water behavior than others. VW`s and BMW`s seem to bead up water that looks just like a really good coating does on paint; right from the factory. Water would form really tight beads and roll right off. My Subaru, and our Acura aren`t as good as the Germans, but they also get pretty tight water beading, but they don`t depart as quickly. My old Mazda, recently departed Toyota, and every rental GM, Ford, Jeep, and Korean car I`ve driven seem to have nothing there. Water sticks and lays on the glass like unprotected paint.

I have no idea what causes the difference and it`s observable on both the windshield and the back glass. In the case of my vehicles I put NOTHING on the glass and I don`t use any sort of wash/wax product. Most of the cars I bought new and there was no dealer protection package or other nonsense applied. The properties remained through the life of the vehicle in my hands, most of the time averaging around a decade. This lead me to think it was something about the glass itself. Am I crazy? Always a possibility.


You could be a prisoner of the aerodynamics.

Quite possible. I did notice last night in the snow the glass would be blown above 60mph, but that doesn`t help much with the majority of my commute is below that speed.


I`m not going to be much help, but RainX is a cheap try, I liked Opti-Glass the couple of times I used it before the sprayer clogged up, and I have some Diamondite that I found to be much easier to apply than RainX, but I stopped using it so I could use up my RainX. I don`t know how those compare to Aquapel, which I have never used. You could also try a wax (ok, I`m a heretic). What about your Mohs EVO? I told you I wasn`t going to be much help.

Thanks. I was looking for something a little more durable than Rainex. I do have some Mohs EVO left over, don`t know why I hadn`t thought about that. I know many here like to use some sort of product on their glass and was open to suggestions since I`ve never messed with it in the past.

[Setec Astronomy]

I think the main problem with the longevity of glass treatments (to your RainX durability comment) is using them on the windshield, where the wipers wear them off. That was the reason I bought Opti-Glass, was because it was supposed to be a special coating that bonded to glass and held up to the wipers. I think you`ve got a lot more flexibility on fixed windows, even if you don`t want to take the time to coat it now, putting something on it, sealant, spray wax, etc., will at least tell you if you`re able to change the behavior so it`s more to your liking, even if it`s temporary.

[Accumulator]

Last time I got an Audi windshield replacement, the new one had that "factory coating" that was kinda like a half-@$$ed, but very durable, version of RainX. Eh, OK...no terrible downside and it was basically OK though I`d prefer it just bare (especially after a few years of hard use).

Desertnate- One more vote for the RainX, which might surprise you durability-wise. And even if it doesn`t, I`d expect doing that backlight to be pretty quick and easy.

[sf_car_guy]

I`ve always just used whatever coating I`m using on the paint for all windows except the windshield (wiper judder and smearing risk)

[PA DETAILER]

I would not over think it. Put on any good spray coating or glass treatment and call it a day.

[Desertnate]

Thanks for the inputs everyone!


I would not over think it. Put on any good spray coating or glass treatment and call it a day.

Good advice. I`ll probably hit it with some left over MOHS and hope for the best. If my bottle has gone bad, I`ll try out some RainX I was really looking to see if there was any glass product people rave about, but doesn`t seem to be the case.

[Fskof]

Why not use Gyeon Q2 Quickview? Very easy to apply, affordable and just works great. I apply it on all the glass on my vehicles. I get about 1 year on the glass and 6 months on the windshield on my cars that are used all year long in Wisconsin weather (sun, heat, humidity, bugs, rain, snow, sleet and ice)

From my experience RainX does not last long.