I was watching a ChrisFix video talking about making the winshield very clean. He notes that he likes using carnauba wax after fully cleaning the winshield glass with cleaner and clay.

However, I was looking carnauba wax online, and found a few odd things. There are different grades of carnauba wax, so I'm not sure which I should get either. I read through a forum that said that carnauba wax is very weak against heat and that I should be seeking a different wax that is more heat resistant. Does the different grades of wax affect this heat resistance? How would I know what is the right type of wax I will need to protect the winshield as best as possible?

  • I prefer using RainX, then using the RainX washer fluid in my reservoir to keep it golden. I don't know whether ChrisFix is using it to protect the windshield or actually just repel water and such, though. It's glass, so protecting the glass isn't a big deal. The windshield wipers will strip the wax after a while of use. The RainX will stay longer and continue to work for quite some time ... a lot longer with the washer fluid. Just a thought. – Pᴀᴜʟsᴛᴇʀ2 Oct 10 '15 at 17:29
  • @Paulster2 ChrisFix has said that RainX isn't as durable as canauba wax but after looking it up online I'm frankly not sure if any of them are resistant to high heat. the issue with our winshield is that, when it rains, water leaves plenty of marks on the winshield. It doesn't just come right off, it actually makes it harder to see, which is why I want to get it fixed once and for all – yuritsuki Oct 10 '15 at 18:00
  • What is the purpose for making the windshield more heat-resistant? If it is to minimize the heat absorbed into the cabin there are far better alternatives. – Zaid Oct 10 '15 at 19:10
  • @Zaid From what I'm reading, the wax used in the protective layer of the winshield (to keep water flowing freely instead of getting stuck) is very susceptible to heat so a coating that may last 5 to 6 months might end up lasting 2 to 3. – yuritsuki Oct 10 '15 at 19:38
  • @thinlyveiledquestionmark Have you considered changing to a different kind of wiper blade? – barbecue Oct 11 '15 at 15:43

tl dr - Rain-X is better than carnauba wax.

I was reading an article by Wired Magazine about Rain-X. The article talks about how Rain-X works and is the basis for why it will (if applied properly) work better than carnauba wax in cool weather or in high heat.

Basically, the main ingredient in Rain-X which makes the water run off is called Polydimethylsiloxanes (PDMS). This substance creates a superhydrophobic surface on the glass which will repel water. The article states:

Polydimethylsiloxanes (PDMS) - A chain of repeating molecular subunits — two organic methyl groups attached to inorganic silicon-oxygen — forms a thin layer on the windshield, and the methyl groups provide low surface tension, which actively repels high-surface-tension fluids like water.

Rain-X also has chlorotrimethylsilane, which it states:

Residue from PDMS synthesis, this compound is regularly used to silanize — that is, chemically neutralize — laboratory glassware so organics won’t stick.

What is organic? Bugs. (As an aside: What's the last thing which goes through a bugs mind when it hits your windshield ... It's BUTT! ... Sorry, had to throw it in.) If this stuff will help keep organic matter from sticking to glassware, it will help keep bugs from sticking to your windshield.

The last thing which helps Rain-X is siloxanes and silicones, di-me, hydroxy-terminated, which the article states:

Fragments of PDMS, broken down by that sulfuric acid we mentioned. The hydroxyl groups help them bond strongly to glass, making it tougher for your wipers to disperse the Rain-X.

This will actually help the Rain-X stay on your windshield because it is bonding to the glass, even if you squirt alcohol based windshield wiper fluid onto it. Carnauba was cannot claim any of these things. It is an organic wax which repels water ... that's about it. There is nothing in it which will help it stay on your windshield when the wipers are going. There is nothing in it which will keep it from washing away when you throw some wiper fluid on it. Due to Rain-X's ability to stay on your windshield, it should outlast the wax in almost any situation.

There have been a couple of things which the blogs/forums will state are issues with Rain-X. One of those things is chitter ... where the wiper will skip across the windshield. I've found if you keep the wiper clean, this problem never occurs. The easiest way to accomplish this is when you are washing your windshield at the gas station, put the squeegee side on the glass under the wiper, the lay the wiper down onto pad side of the squeegee. Pull the squeegee out from under the wiper and see all the crap which comes off of the wiper. It will work a lot better as well. Also, usually when you start getting chitter, it's time to reapply the Rain-X. You can postpone this by using the Rain-X brand of washer fluid.

Another issue which may occur with Rain-X is after application, you may see swirl marks. There are two things you can do to alleviate this. First, only apply the one direction, such as horizontally. Second, you need to ensure you are following the directions correctly by using a wet applicator. Thirdly, use a clean damp cloth to wipe the are after its dry. A microfiber towel works wonders here.

Please note: This is not an advertisement for Rain-X. I do not work for Rain-X, but I do endorse their product (unfortunately for free). When used correctly, Rain-X works wonders. It absolutely works great at night when it's raining for being able to see what's going on around you. It will keep your windshield free of water, especially at speed.

  • I thought the OP was interested in something that resists heat, not water. – Zaid Oct 11 '15 at 8:30
  • @Zaid - The whole point of the diatribe was that Rain-X will stick better to the windshield than carnauba wax in any situation. Maybe I didn't spell it out that way, though. – Pᴀᴜʟsᴛᴇʀ2 Oct 11 '15 at 11:51
  • I only use Rain-X for windscreens. I dislike the coating waxes give. And a good Rain-X coating here means I don't need to use my wipers for up to a couple of months - even in winter – Rory Alsop Oct 12 '15 at 7:55
  • There are alternatives to Rain-X. CQuartz makes one. In a pinch you can also cut a potato in half and wipe the potato starch on the windshield. – Zaid Oct 12 '15 at 12:33
  • @Zaid, Ha, you have to be pretty hard up to rub potatoes on your windshield. But now I'm curious if that works at all. – JPhi1618 Oct 12 '15 at 20:07

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