The haze on the inside of your windscreen is outgassing — plasticisers evaporating out of your warm dashboard and condensing on cool glass. It is an oily film, not dirt, which is why a dry wipe just smears it around.
On the outside, glass gets water spots worse than paint does because it is harder and flatter, so mineral deposits sit and etch without the softer buffer clear coat provides. Both are fixable; neither responds to more window cleaner.
Glass is one of two things people notice in the first ten seconds of getting back into a car. The other is smell.
Your dashboard is plastic and vinyl, and those materials contain plasticisers that keep them flexible. When a car sits in sun the dash gets hot — far hotter than the cabin — and those compounds slowly evaporate out of it.
They condense on the coolest surface available, which is the glass. Over months that builds an oily, light-scattering film across the whole windscreen, worst along the bottom where the dash is closest and along the top where the angle is shallowest.
You mostly do not notice it until you drive into low sun or oncoming headlights, at which point the entire screen glares. That is the film scattering light, and it is a genuine safety issue rather than a cosmetic one.
Two things make it much worse. Smoking in the car adds tar to the mix, which is why a smoker's windscreen goes brown-yellow. And silicone-heavy dashboard dressings — the ones that leave a wet shine — give the process more to outgas.
The fix is a dedicated glass cleaner and, importantly, two towels: one to break down and lift the film, a second dry one to buff. One towel just redistributes the oil, which is why people conclude their glass cleaner is useless.
Otherwise you cannot tell which side a remaining smear is on, and you will chase it back and forth. Outside, then inside.
Overspray lands on the dash, the door cards and the headliner. Spray onto the towel instead. On a windscreen, spraying at the glass also runs product straight down into the demister vents.
One damp with cleaner to lift the film, one dry to buff. Waffle-weave glass towels if you have them. The second towel is what removes streaking, and skipping it is the single most common cause of a smeary result.
Horizontal on the outside, vertical on the inside, or the other way round. If a streak survives, you instantly know which side it is on.
Where the glass meets the trim. It is awkward, it is where the film is heaviest, and it is the part everyone misses. Fold the towel over a finger or use a glass tool with a low-profile head.
The top edge of a side window is hidden in the door seal when it is up, and it is filthy. Clean that strip or you get a dirty line the moment you open the window.
On a hatchback the rear glass gets the worst of the road spray and is usually the dirtiest piece of glass on the car.
Water spots on glass behave like water spots on paint, only worse. Glass is harder and flatter, so mineral deposits sit tight and there is no soft clear coat to absorb any of it. San Francisco's hard water and constant fog wetting make this one of the most common complaints we get about glass specifically.
The same escalation applies: a fresh deposit washes off, a bonded one needs a dedicated remover, and one that has genuinely etched into the glass needs polishing — glass polishing is a real process, and it is a different job from paint correction. Sprinkler overspray is the usual culprit, and the tell is a concentrated pattern on one side of the car only. The water spot guide covers the diagnosis.
Wiper streaking is usually not the wipers. Before replacing blades, clean the glass properly and then wipe the rubber edge of each blade with a damp cloth — the amount of black grime that comes off is often the entire problem. A blade dragging across a contaminated screen streaks no matter how new it is.
If streaking survives clean glass and clean blades, then the blades are worn and worth replacing. And if the screen has a coating on it, remember a worn blade drags across that coating and wears it faster than anything else.
A coated windscreen is genuinely one of the best coating upgrades there is. Water sheets off at speed rather than pooling, which noticeably improves visibility in rain and reduces how much you need the wipers at all. See what can be coated.
Interior glass is part of every interior detail; exterior glass is part of every exterior job. Neither is an add-on, and both include the edges people miss — the top of the windscreen and the hidden strip on the side windows.
If the outside glass has spotting that survives a wash, that is decontamination or polishing territory and we will tell you which after seeing it.
More short answers live on the FAQ.
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One to lift the film, one to buff. Glass is included in every service we run.