Window and glass cleaning

Clean your car windows before low sun shows up the film

What does window and glass cleaning cover? Three separate jobs: glass cleaners cut the greasy film inside and out, screenwash keeps the windscreen clear while you drive, and de-icers free up frozen glass. On top of that comes glass polish, which takes off etched-in water spots and old coatings before you seal the glass.

Window and glass cleaning covers everything that gets the glass on your car clear again: the cleaner you use by hand, the fill for the washer system, the de-icer for frosty mornings and the glass polish for residue no cleaner will shift. Cleaning car windows isn't cosmetic. A film on the windscreen scatters low sun and the headlights of oncoming traffic, and those are exactly the moments you need to see.

• Three jobs, three products. Glass cleaner takes the film off by hand, screenwash works while you drive, de-icer only comes out when it freezes. Mix them up and you end up topping the tank with summer screenwash in autumn, even though it can freeze, or hoping the washer jets will somehow reach the haze on the inside.
• Material compatibility matters as much as cleaning power. In two 2026 tests by AUTO BILD covering 16 screen cleaners and de-icer sprays between them, two products attacked polycarbonate, the plastic many headlight lenses are made of. Whatever runs off the glass also hits everything next to it.
• Screenwash with methanol has been off the consumer market since 2019. Since May 2019, windscreen washer and de-icer fluids containing 0.6 % methanol by weight or more may no longer be sold to private buyers. Methanol is a toxic alcohol that used to act as the antifreeze in these fluids. For you, that means whatever you buy for the tank as a private customer today has to do without that much methanol.

Detailing1's day-to-day tip: Mix a glass concentrate with tap water and your spray bottle puts the limescale you just took off the outside straight back on the glass. Koch-Chemie specifies anything from neat to 1:3 for the Koch-Chemie Glas Star "Gla" glass cleaner concentrate, ideally mixed with RO (reverse-osmosis) water. And before the first bottle goes on the inside, check whether the side and rear windows have tint film. Tint film is no place for cleaners containing ammonia or sal ammoniac, vinegar or abrasives.

The film on the windscreen only dazzles you against the light

A greasy film on the windscreen barely shows in daylight from the front and only becomes visible once low sun or oncoming headlights shine through the glass.

On the outside, the film is made up of bug remains, dust, silicone, wax and diesel soot. That's how Dr. Wack describes it in the product information for its CW1:100 screen cleaner: the washer system only takes these layers off at the surface and leaves behind a water-repellent, milky haze that scatters light. That's a manufacturer claim, and it lines up with what drivers describe in forums when, after a year, the wipers do nothing but smear.

On the inside, the film builds up with no help from outside. Dashboard plastics give off compounds when they warm up, and those settle on the cooler glass. Why household cleaners smear on it and which chemistry actually shifts the haze is covered in the glass cleaner category. How the haze forms in summer is explained in our guide to interior window haze.

That's why streaks on the windscreen never have just one cause. Outside, the wipers spread whatever the washer leaves behind; inside, the dashboard film keeps coming back. If you want to clean the inside of the windscreen, you need a different approach than for the outside, and it's often the inside that blinds you against the light.

It's a seasonal job. According to Google Trends, search interest in cleaning car windows in Germany peaks in September. From then on, the sun sits low again on the morning commute. Give the glass a proper going-over in autumn and you head into the dark months with a clear view.

Glass cleaner, screenwash and de-icer do three different jobs

Glass cleaner takes the film off by hand, screenwash cleans while you drive, de-icer frees up frozen glass, and none of the three can stand in for the others.

Glass cleaner is the tool for the thorough session, whether you want to clean car windows on the inside or clean car windows on the outside. Concentrates like Glas Star you mix up yourself. Ready-to-use sprays like the Koch-Chemie Glass Cleaner "Gc" glass cleaner go on the towel rather than the glass when you work inside, so no overspray lands on the dash and screens. Glas Star has several verified reviews on Trusted Shops, and one simply calls it the best stuff for clear glass.

Home remedies often top the list when people hunt for the right product. Skip the methylated spirits that gets passed around as an insider tip for cleaning car windows: according to AUTO ZEITUNG it leaves streaks. For the inside, the magazine recommends a silicone-free glass cleaner from a specialist retailer and buffing dry until the glass squeaks.

Screenwash works while you drive. It has to shift bugs and road film without you pulling over, and it has to suit the season, because a straight summer screenwash can freeze. De-icers only come out on frosty mornings and melt ice that's already sitting on the glass.

The fourth stage is glass polish. It takes off what a cleaner can't dissolve and preps the glass for a sealant. The tool for every stage is a set of glass towels that never touch anything but glass. Any trace of interior dressing or wax in the towel comes back as a streak on the glass, which is why a towel like the Koch-Chemie Pro Glass Towel 230GSM microfibre glass towel is kept apart from all your other towels.

All four areas sit under Cleaning, because their job is getting dirt off. Glass cleaners with added sealant leave a thin protective layer as a bonus, but proper protection lives under window and glass protection. Glass comes last in every detailing session: outside after the wash, inside after the interior clean. Start with the glass and you'll end up doing it twice.

Tint film and polycarbonate limit which glass cleaner you can use

Not every surface around the glass can take every cleaner: tint film, polycarbonate headlights and coated glass set the limits before cleaning power even comes into it.

According to AUTO ZEITUNG, cleaners containing sal ammoniac or ammonia, enzyme-based cleaners and abrasive cleaners have no business on tint film, and the vinegar in household glass cleaners can damage it. The recommendation is water and a soft cloth. The magazine also says to leave the film edges alone completely. If you need more than water, reach for an ammonia-free formula like the INNOVACAR "0" Ammonia Glass cleaner and check the film manufacturer's approval first.

Polycarbonate is a tough, crystal-clear plastic that many headlight lenses are made from. It looks like glass but behaves differently: some cleaner ingredients cause fine cracks, especially when the material is under stress. What that means for you: whatever you spray on the windscreen or spread with the washers, the headlight right next to it has to cope with too. One customer asked about windows made of Makrolon, a polycarbonate, and the same caution applies there.

Within the range, too, every product has its surface. Koch-Chemie describes Glas Star as alcohol-based and meant for smooth, alcohol-resistant surfaces. Soft99 rules out its Glass Compound, a glass polish with abrasive particles, for interior glass, plastic, paint and glass with a water-repellent or anti-reflective coating, and says it shouldn't be used in direct sun.

The glass itself sets a limit as well. If it's already sealed and you want that layer to last, leave the glass polish on the shelf: according to the manufacturer, it strips old glass coatings, and with them exactly the layer you want to keep. For sealed glass, a glass cleaner that won't attack the coating and a clean towel are all you need.

An honest word on ready-to-use sprays: one Trusted Shops review of Gc reports needing two to three passes. With stubborn film, several light passes are the way to go; piling on more cleaner in one go isn't, because the excess dries into a ring at the edges.

Your washer system only cleans as well as what's in the tank

The washer system can only spread what's in the reservoir: if the fill doesn't suit the season, the film stays on the glass, or a straight summer screenwash freezes at the first frost.

AUTO BILD's 2026 test of eight summer screen cleaners shows how tough the job is. The products had to shift bug grime and water-repellent dirt made of soot, silicones and hydrocarbons, each over ten wipe cycles with 50 millilitres. On top of that came material tests on paint and on polycarbonate held under stress for 24 hours at 80 °C.

When a manufacturer like Dr. Wack explicitly designs its screen cleaner for plastic headlight lenses and fan-spray jets, it tells you just how far the fluid travels: into the jets, over the headlights, along the seals. So screenwash has to do more than get glass clean. It mustn't attack the surfaces around it either.

In winter, antifreeze goes in the tank. How much cleaner concentrate can go into the antifreeze mix, and in what order you mix, is set by each manufacturer for its own product. Dr. Wack, for example, specifies pre-diluting the antifreeze concentrate and pre-mixing the components separately. There's no blanket figure that holds for every product. The label is what counts.

The screenwash category collects the concentrates for the tank. Even so, it's no substitute for a thorough session by hand: no washer system reaches the haze on the inside, and on the outside it only removes what the wipers can reach.

De-icer clears ice on the glass, antifreeze protects the tank

A de-icer melts ice that's already sitting on the glass, while antifreeze in the screenwash keeps the reservoir, lines and jets from freezing. Two jobs, two products.

The way AUTO BILD tested eight de-icer sprays in 2026 shows what matters: a cold chamber at −19 °C, 35 sprays, 130 seconds of dwell time. Scores covered de-icing, material compatibility, smell and refreezing. According to the test, the sprays are mostly alcohol, plus a share of antifreeze so the thawed glass doesn't ice straight back over.

Refreezing is the criterion you can't see on the shelf. The glass is clear, and as you pull away, the cold locks the leftover moisture back in place. That's exactly the moment the antifreeze in a de-icer is there for.

In driver forums, people ask whether more antifreeze in the tank makes de-icer redundant. The answer lies in the job: antifreeze protects the system, de-icer protects the glass that's already iced over. Keep the two apart and you won't waste money on either. You'll find sprays for frosty mornings under de-icers.

Keep the material question from earlier in mind. De-icers run off the glass onto seals, wiper arms and headlights. One spray attacking polycarbonate in the test is no reason to go without, but it is a reason to spray sparingly and aim at the glass.

Glass polish comes before every glass sealant

No glass cleaner shifts etched-in water spots or old coatings: they have to come off mechanically, and every glass sealant needs exactly this deep clean before it can bond to the glass.

The Soft99 Glaco Glass Compound Roll On glass cleaner works with two types of abrasive particle and, according to the manufacturer, removes traffic film, water spots and old glass coatings. Soft99 explicitly positions it as prep for a glass sealant. In our orders it's often bought together with a glass sealant from the Glaco range, and that's exactly the right sequence.

In forums, drivers describe etched water spots on glass that survive several passes with cleaner and only disappear with polish. That's not the cleaner failing. Limescale that has etched into the glass is no longer a film a solvent can pick up; it's a deposit that has to be abraded. More glass cleaner gets you nowhere there, a glass polish does.

After the polish comes protection, and that's no longer part of cleaning. Sealants, rain repellents and anti-fog products are grouped under window and glass protection, and the coatings themselves live under glass sealant. Skip the polish and you seal the old film in with it, and the new layer only holds as well as whatever it's sitting on.

The most honest test for your glass costs nothing. Drive into low sun and see what shows up: streaks the wipers push around are on the outside; a haze they don't touch is on the inside; pale rings that a second pass won't shift are etched in and a job for polish. That way you know which job comes first before you've lifted a finger.