Can I put a ceramic coating on my windscreen?
Quick answer: You can, and the chemistry is well suited to it -- but we advise against the front windscreen. A coating makes water cling to the wiper blade instead of the glass, and most drivers who have it done end up regretting it. We coat all the other glass as standard and leave the front screen alone.
It is one of the more common questions we get when someone books a coating: if the stuff repels water so well, surely the windscreen is exactly where you want it? Professional ceramic coatings are optically clear and strongly hydrophobic, so on paper they make ideal glass coatings. The reality is more nuanced, and it comes down to one moving part: the wiper.
What coated glass actually does for you
Start with the upside, because it is real and most drivers underestimate it. Picture a wet night: you walk out to the car and most of the rain has already beaded up and rolled off the side glass, leaving a scatter of droplets behind. Pull away, and the airflow over the car clears most of what remains -- by the time you reach the end of the road the side windows are close to clear. No constellation of droplets catching every streetlight, no leaning forward to read the junction.
The faster you go, the better it works. Seventy on the motorway is roughly the same as holding a hairdryer to the glass at full blast; rain barely gets a foothold and you can often go a long way between wiper sweeps. Below about 30mph the airflow drops away, but gravity takes over and pulls the droplets straight down and off the bottom edge instead. Either end of the speed range, the water has somewhere to go.
It earns its keep on cold mornings too. On a light frost, a degree or two under, coated glass frequently carries no frost at all while the bonnet is white over. In a harder frost it will still ice up, but the ice releases sooner and scrapes away with far less effort. And there is the look of the thing: glass is maybe a fifth of the car's surface, yet clean glass makes the whole car read as far cleaner than it is. Coated glass stays clearer for longer between washes and is plainly safer to see through.
The trouble starts at about 30mph
So if it is that good, why leave the front screen bare? The problem lives in the middle of the speed range. At roughly 30mph the airflow pushing water back over the screen and gravity pulling it down are about evenly matched, so droplets neither blow off nor run off cleanly -- they sit there and loiter. On the side windows this barely matters. On the screen you are looking straight through it, and you reach for the wipers.
That is where the hydrophobic surface turns against you. Because the water will not adhere to the glass, the wiper does not push it aside in the usual way; instead the water gathers into a band that clings to the blade and travels with it. You get a trailing puddle, typically about an inch across, chasing each sweep across your line of sight. Some people find it a mild novelty. Most find it genuinely distracting, and the large majority of customers who have asked us to coat the front screen have come back wishing they had not.
Tom, our operations manager, has a stock line for anyone who insists: it is the one part of the car where the coating fights the only tool designed to clean it. The wiper and the coating want opposite things, and on the front screen the wiper has to win.
Then there is what the coating does to your wipers
The trailing puddle is the headline complaint, but it is not the only one. A hydrophobic screen changes how the blade itself behaves, and not for the better. On bare glass a wiper rubber rides on a thin film of water that it is constantly clearing; the film lets the blade glide. Take that film away -- which is exactly what the coating does, since the water no longer wets the surface -- and the rubber drags rather than slides. You hear it before you see it: judder, chatter, that stop-start squeak across a screen that is nearly dry but not quite.
Drivers who coat the front screen often find they are changing blades sooner, because the rubber wears unevenly when it is chattering instead of gliding. Some get on better with a softer or silicone-edged blade; others end up adjusting wiper arm tension to stop the skipping. None of it is insurmountable, but it is a string of small annoyances that you simply do not have on an uncoated screen, and they tend to surface a few weeks in, once the novelty of the beading has worn off. It is the kind of thing nobody mentions in the sales blurb.
Rain sensors and the modern screen
One more practical wrinkle, and a more recent one. A lot of cars now have a rain sensor tucked behind the mirror that reads how much water is sitting on the glass and sets the wiper speed for you. That sensor is calibrated for the behaviour of water on bare glass. Make the glass aggressively water-repellent and you change what the sensor sees: water that would normally pool and trigger a sweep instead beads up and scatters, so the automatic wipers can read the screen as clearer than it really is and lag behind the conditions. We have had cars in where the owner could not work out why the auto-wipe had gone lazy, and the answer was a glass treatment a previous owner or valeter had applied.
It is not a universal problem -- sensitivity varies by manufacturer, and some systems cope fine -- but it is one more reason the front screen is a special case rather than just more glass to coat. The rear screen and side windows have no such sensor to confuse, which is part of why we are happy to coat them without a second thought.
Borrow the experiment from a bottle of Rain-X
None of this is unique to ceramic coatings. Rain-X and similar glass sealants produce the same wiper behaviour for the same reason -- they make the glass hydrophobic. The useful difference is reversibility. If you try Rain-X on your front screen and decide the trailing puddle drives you up the wall, a wipe of isopropyl alcohol takes it back off. A cured ceramic coating is not coming off without abrasion.
So if you are genuinely curious whether you could live with the effect, that is the honest way to find out: put Rain-X on your own screen for a few weeks and see how you get on in mixed conditions. It will show you the trailing puddle, the wiper judder and any rain-sensor oddity all at once, which is the whole point -- it is an accurate preview of what a ceramic coating would feel like, with none of the commitment. Plenty of drivers try it, shrug, and clean it off, which tells you most of what you need to know about coating the screen permanently.
Not everything sold as a "ceramic glass coating" is one
A word of warning on what you buy if you go shopping yourself. The shelves are full of products badged as ceramic coatings for glass that are nothing of the sort. Many are wax-style sealants with a few ceramic beads thrown in to ride the marketing wave, and they lean heavily on silicone oils to manufacture the water-repelling effect.
That silicone chemistry is far older than true ceramics, and it has a history you do not want on your glass: it was the trick used to mask fine scratches on tired paint by scattering light. An oily film that diffuses light is the last thing you want between you and the road, especially with low sun or oncoming headlights picking out every smear. A genuine coating bonds clear and hard; a silicone sealant sits on top and smears. Read the data sheet, not the front of the bottle.
What we coat, and what we leave
When a car comes in for a coating, we treat the glass that benefits without fighting back: the side windows, the rear screen, any sunroof glass, the headlights and the door mirrors. Each gets the same prep as the paint -- a proper decontamination and a clay so the surface is genuinely clean before anything bonds to it, because a glass coating laid over road film and old wiper smear will not last and will not look right. The front windscreen we leave uncoated as a matter of course, because we would rather you never noticed the coating than noticed it every time it rained at 30mph.
If you have read all of the above and still want the front screen done, that is your call and we will do it -- at no extra charge, just tell us when you book. We would just ask that you try the Rain-X experiment first, because it is a lot easier to scrub a sealant off your own screen than to grind a cured coating off ours. And if you do go ahead, budget for a fresh set of wiper blades to go with it; new rubber on coated glass behaves far better than the tired blades that were happy enough on bare glass.
For the wider case on why drivers coat the paint in the first place, see What are the benefits of a ceramic coating?.