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Rain-X - The Review

Testing window treatments for clarity of vision.

by Julian Edgar

Click on pics to view larger images

Rain-X is a product that's been around for decades. Some people swear by it; others swear at it! So what is it and is it any good? We bought a bottle - and also grabbed some Rain-X Anti-Fog at the same time.


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Variably described on the plastic bottle as 'The invisible windscreen wiper', as 'letting you see clearly' and said to 'repel rain, sleet and snow', the product is made in the US by Blue Coral-Slick 50 Ltd. Slick 50? You ask. Yeah, that's what we thought too - but always test a product on its own merits, we decided... Not particularly cheap (a 100mL bottle costs anywhere from $8 to $12, depending on where you buy it), the vaguely alcohol-smelling liquid is designed to be applied to the outer surface of car windows.

The instructions actually specify that you should:

  1. Clean the glass.
  2. Apply Rain-X with a small, folded dry cloth.
  3. Allow to dry, then polish window until clear.

Well, we've shortened them slightly but that's pretty well what they say, anyway. The stuff goes on without problems - it doesn't smear, for example - and so it takes only about 5 minutes to apply. I did both the front and rear glass on my Audi S4 - the choice of car is important because the performance of Rain-X we discovered to be affected by the angle of the glass. The Audi has very laid-back front and rear 'screens.

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The worse thing about testing Rain-X is waiting for it to rain after you've applied it! Sure, you can apply the washers but that's not very realistic, is it? Anyway, after a few days it started to rain very gently, and immediately it was noticeable that the water beaded all over the screen. In these conditions, visibility is actually worse than without the stuff applied, but once more rain starts to fall, the beads soon coalesce and then an amazing thing happens. At speed, the water just shoots over the top of the car! It slides off so easily that you're looking through basically clear glass, even though it's raining heavily and the windscreen wipers are stationary.

Of course, in some situations you do need to use the wipers - and that's the downfall of Rain-X. Not because the result is smeary - though it is slightly different to normal - but because the physical scraping action of the rubber slowly removes the Rain-X from the surface. How slowly? Not very, actually. Within two weeks of occasional windscreen wiper use - in the occasional rain that occurred - the affect of the Rain-X was noticeably diminished. You could see this by watching drops on the windscreen. They slowly tracked across the swept area of the glass then accelerated like hell when they got to the area of the windscreen treated with Rain-X but unscraped by the wiper blades.

So when it was on, the results were exceptionally good. But to keep it on, you'd have to apply it probably every fortnight in the conditions we experienced. On that basis, a bottle would last a few months.

And what of the back window? As with most sedans, the Audi doesn't have a rear wiper. And, while the airflow down the rear screen is attached and not turbulent, the strength of this airflow isn't anywhere near as strong as on the front screen. I was hoping that the Rain-X would cause this water to run off, keeping the rear view clearer. But instead the water tended to form into globules - not much change in the rear vision, really. Maybe this would have been better on steeper glass - on a wagon, for example.

We also tried Rain-X on another car - one that had that common problem of smearing wipers, yes, even with the rubbers replaced. With Rain-X applied, the smears disappeared magically, and at the time of writing, had yet to appear.

Summary? Good stuff - magical in fact sometimes - but with the on-going maintenance of requiring frequent re-applications.

Rain-X Anti-Fog

Click for larger image

A more recent addition to the range, the Anti-Fog treatment appears to be made by a different company - the Unelko Corporation. No matter; it's marketed under the same Rain-X brand. This stuff's so much alcohol that you could prob drink it, but it's actually sold to wipe over the interior of glass. Doing this prevents interior fogging, misting and steaming, apparently. It's said to be suitable for the inside of car windows, for bathroom mirrors, for helmet visors and so on. We decided to try it in the steamiest area we could find - the bed-, oops, the bathroom.

And did it work? Well, kind of. The fogging of the mirror was obviously reduced, but you still couldn't see anything in the mirror anyway. It wasn't the radical change caused by the Rain-X, that's for sure.

At $8 for the Rain-X Anti-Fog, it might be worth it if you have a particularly thorny fogging problem, but it's not a product to buy as a matter of course.

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