How does Rain-X work?

By Product Expert | Posted in FAQs, Just for Fun on Saturday, August 22nd, 2020 at 2:38 pm
Beaded up raindrops on a windshield

Solving the Magical Mystery of Rain-X

Rain-X seems almost like a magic chemical. Treating a glass surface with the substance works wonders in the way water reacts. How does it repel water in the way that it does? Join us as we take a dive into the workings of Rain-X on a chemical level.


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In a simple sense, Rain-X repels water, causing it to bead up and roll off of glass surfaces. By nature, water sticks to glass and spreads out instead of rolling off. Rain-X repels water similarly to the way that oil does, and this causes the H20 to go bye-bye.

Blue 2020 Volkswagen Tiguan parked at a crosswalk in the rain
Rain doesn’t stand a chance against the 2020 Volkswagen Tiguan.

How does Rain-X work chemically?

Okay, you really want to get into this? The way Rain-X works chemically is a bit complicated (especially to a not-so-scientifically-inclined brain like ours), but stay with us and it should come across.

On the chemical level, glass consists of a network of bonded silicon and oxygen atoms. Scanning this network, the (extremely) close observer will notice an occasional exposed OH or hydroxl group. Water is naturally attracted to the hydroxl groups, and, as a result, water sticks to glass and spreads out.

Rain-X consists mostly of something called Polydimethylsiloxane (PDMS). Try saying that five times fast (ba dum tss). The carbons in PDMS are non-polar, just like the carbons in oil.

Water, on the other hand, is polar. This difference in polarization causes water to repel substances like oil and Rain-X. As a result, when water lands on a Rain-X treated windshield, this repellence causes the water to ball up into a sphere, touching as little of the windshield as possible. These balls of water run off the glass surface very easily. This state of affairs is quite a bit more desirable to the average driver than the typical sticky, spready interaction.

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