What grit should I start with on foggy headlights?

It depends on severity. Light-to-moderate yellowing usually starts at 600 grit. Heavy, deeply oxidized or slightly rough lenses need a coarser start around 400, or occasionally 320 for the worst cases. You want the coarsest grit that removes the damage efficiently, then work finer from there.

Do I really have to use every grit in order?

Yes — this is the rule that makes or breaks the job. Each grit removes the scratches left by the previous one. If you jump from 600 straight to 2000, you'll leave deep sanding lines the fine paper can't erase, and no polish will save it. Step through them: 400 or 600, then 800 or 1000, 1500, 2000.

Why must the sandpaper stay wet?

Water lubricates the paper, floats away the plastic dust, and stops the grit from clogging and gouging. Dry-sanding polycarbonate leaves deep, uneven scratches and can even melt the surface from friction heat. Keep the lens and paper soaking wet the entire time and re-spray constantly.

How do I know when I've sanded enough at each grit?

The lens should look uniformly frosted with no clear or glossy patches left. Any shiny spot is un-sanded oxidation. Sanding each new grit in a direction 90 degrees to the last makes it easy to see when the previous grit's scratches are gone — keep going until the old direction of scratches has completely disappeared.

Wet-Sanding Headlights: Grit Progression & Technique

Written & researched by Kenji Mori Detailing & Paint Protection Editor

Updated July 2026

Wet-Sanding Headlights: Grit Progression & Technique — a car headlight shown half foggy and yellowed, half crystal clear

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Short version: Wet-sanding is how you physically remove real headlight oxidation. Keep everything soaking wet, start with the coarsest grit the damage needs (400 for heavy, 600 for moderate), and step up through 800/1000, 1500 and 2000 without skipping any. Change sanding direction with each grit so you can see the old scratches disappear. Uniform frost means you're done at that stage.

When a headlight has gone properly yellow, no polish on earth will fix it, because the damage is a layer of oxidized plastic that has to be physically removed. That means sanding. It sounds scary — you're taking sandpaper to your car — but done right it's controlled, safe and the single most effective step in the whole restoration. Here's exactly how to do it without wrecking anything.

When you actually need to sand

Not every foggy lens needs sandpaper. Run your fingernail across it. If it feels smooth and only looks lightly cloudy, you may get away with compound and a polish alone — that's the easy path in the full restoration guide. But if the surface feels rough, chalky or catches your nail, or the yellowing is deep, you're into sanding territory. That oxidation is baked into the plastic and only abrasion removes it. If you want the background on why the plastic degrades like this, we cover it in why headlights fog up.

Wet-sanding, and why the water matters

The "wet" in wet-sanding isn't optional — it's the whole technique. The water does three jobs at once: it lubricates the paper so it glides instead of grabbing, it floats away the fine plastic slurry so the grit doesn't clog, and it keeps friction heat down so you don't melt or gouge the polycarbonate.

So before you touch the lens: fill a spray bottle with clean water (a single drop of car soap helps the paper slip), soak your sandpaper for a minute, and keep spraying the lens constantly as you work. If the paper ever starts to drag or squeak, it's too dry — stop and re-wet. Dry-sanding, even for a few seconds, leaves deep uneven scratches that ruin the finish.

The grit progression

This is the part people get wrong, so read it twice. You start coarse to remove damage fast, then step up through progressively finer grits, and each grit must remove the scratches left by the one before it. A typical progression:

Start: 400 grit for heavy oxidation, or 600 grit for moderate. (The very worst, rough lenses might begin at 320.) This does the real cutting — removing the yellow layer.
Then 800 or 1000 grit to erase the coarse scratches from step one.
Then 1500 grit to refine further.
Finally 2000 grit to leave a fine, uniform frost that polishes up clear.

Never skip a grit. Jumping from 600 to 2000 feels faster, but the fine paper can't remove the deep 600-grit scratches, so you're left with sanding lines that no compound will polish out. Every skipped step costs you far more time later than it saved. This is the number-one mistake in the whole restoration — patience through the grits is everything.

The cross-hatch technique

Here's the pro trick that makes the progression foolproof. Sand each grit in one consistent direction — say, left to right in straight, even, overlapping strokes. Then when you switch to the next finer grit, sand at ninety degrees to the last — top to bottom. Now the scratch pattern is crossing the previous one, so it's obvious when the old direction of scratches has vanished. When you can no longer see the previous grit's lines, that stage is done.

Use even, moderate pressure. You're not muscling it — let the grit do the work and keep it wet. Cover the whole lens uniformly. Any glossy or clear patch you leave behind is un-sanded oxidation that'll show through your final polish.

Knowing when each stage is finished

After your first coarse grit, the entire lens should look evenly, uniformly frosted — a consistent milky white with no shiny survivors. That uniform frost is the goal at every stage; only the fineness of it changes as you climb the grits. By the time you finish 2000, the frost should be so fine and even that it almost looks satin. That's your cue to move on to compounding.

What comes after sanding

Sanding gets you to a uniform frost — it does not, on its own, give you a clear lens. The clarity comes back in the next stages: compound and polish cut that fine frost down to optical clarity, then you seal it. Do not stop at sanding thinking you're nearly there and just wipe it — you'll have a dull lens. And whatever you do, don't skip the seal at the end; sanding removes the last of the UV coating, so bare plastic will re-yellow fast without it. We explain why that final step is critical in sealing headlights so they stay clear.

Want it faster? Use a drill

Hand-sanding works perfectly but takes time and effort. If you'd rather speed things up and get a more even result with less fatigue, drill-attachment sanding discs step through similar grits mechanically. They're especially worth it if you're doing more than one car. We cover the options in drill-attachment kits. The same rules apply though — keep it wet, and don't skip grits.

That's wet-sanding demystified. Keep it wet, start coarse enough to remove the damage, climb the grits without skipping, cross-hatch so you can see your progress, and finish at a uniform fine frost. Get the sanding right and the rest of the restoration is easy — this is the stage that decides whether your headlights come out crystal clear or quietly hazy.