Quick answer: To wet sand: soak waterproof silicon carbide paper for 10–15 minutes, wrap it around a soft block, keep the surface flooded with soapy water, and sand in light, straight, overlapping strokes – changing direction 90 degrees at each grit change. For automotive paint, start at 1000–1500 grit to level orange peel or runs, finish at 2000–3000, wipe dry to check, then compound and polish to bring the gloss back. For metal, start at 180–400 and work up to 800 or finer before buffing. Never skip a grit and never skip the polishing step.
Wet sanding is used across metalworking, woodworking, plastics and auto body work for the same reason: it takes out the scratches left by dry sanding and produces a flat, even, glossy-ready surface while removing almost no material. Here's the full process. If you want the "what and why" first, read what is wet sanding.
What you need
- 9" x 11" wet/dry sheets – silicon carbide on a latex-treated backing that stays intact when soaked. Silicon carbide is sharper and harder than aluminum oxide, which is why it cuts cleanly at very fine grits. The same sheet works dry, hence "wet/dry".
- A soft sanding block – rubber or foam. Fingertips leave grooves.
- A bucket of water with a few drops of dish soap, and a spray bottle to keep the surface wet.
- Clean microfiber towels to wipe the slurry off and inspect.
- For paint: masking tape for edges and body lines, then cutting compound, polish and a machine or hand pad to finish.
Step by step: wet sanding paint and clear coat
- Wash the panel and mask any edges and body lines – the clear is thinnest there and cuts through in seconds.
- Soak the paper for 10–15 minutes. Cut sheets into quarters and wrap one around the block.
- Flood the surface with soapy water. There should always be a film of water between paper and paint.
- Start with the coarsest grit the defect needs – 1000 for heavy orange peel or runs, 1500 for light texture or dust nibs, 2000 for a scratch in cured paint. Sand in straight strokes, light pressure, overlapping by half. Don't sand in circles.
- Wipe and check. Squeegee or towel the panel dry. The surface should look uniformly dull. Shiny low spots mean you're not level yet; keep going, gently, until the dullness is even.
- Move up a grit – 1500, then 2000, then 2500 or 3000 – and turn your stroke direction 90 degrees each time. That way you can see exactly when the previous grit's scratches are gone.
- Compound and polish. Wet sanding leaves a fine, even haze. Cutting compound removes the 2000–3000 grit scratches and polish restores full gloss. This is not optional.
Step by step: wet sanding metal
- Dry sand or grind first to remove the heavy scratches and shape the part. Wet sanding won't remove stock.
- Start wet at 180–320 grit depending on how coarse the surface is, sanding in one direction only.
- Step to 400, sanding at 90 degrees to the last grit until every 320 scratch is gone. Keep re-wetting – metal swarf is heavier than paint dust and needs to be flushed constantly.
- Continue to 600, 800 and finer as the finish requires. Stainless and aluminum for a mirror finish typically go to 800–1500 before buffing.
- Buff with compound on a cloth wheel. See buffing wheels and compounds.
Grit progression
| Surface | Sequence | Then |
|---|---|---|
| Fresh clear coat, orange peel or runs | 1000 → 1500 → 2000 → 3000 | Compound, polish |
| Light dust nibs in clear | 1500 → 2000 → 3000 | Compound, polish |
| Scratch in cured paint | 2000 → 3000 | Compound, polish |
| Steel or stainless to mirror | 180 → 320 → 400 → 600 → 800 → 1200 | Buff |
| Aluminum to mirror | 320 → 400 → 600 → 800 → 1500 | Buff |
| Plastic, acrylic, headlights | 400 → 800 → 1500 → 2000 → 3000 | Polish |
| Wood finish between coats | 400 → 600 | Next coat |
| Wood finish, final rub-out | 600 → 1000 → 1500 | Polish or wax |
Increase by no more than double the grit number at each step. If you start at 800, go to 1000 or 1500 – not 3000. Skipping grits is the most common reason a wet-sanded surface still shows scratches after polishing.
Mistakes to avoid
- Too much pressure. Let the paper and the water do the work. Pressure cuts through clear coat and gouges soft metal.
- Letting it go dry. The moment the paper drags, add water. Dry spots load the paper and leave deep scratches.
- Sanding edges and body lines. Mask them. Paint is thinnest there.
- Circles. Straight strokes, rotated 90 degrees per grit, so you can read your progress.
- Too much water on wood. Wood absorbs water and swells. Use a damp surface, not a flooded one.
- Stopping before polishing. A wet-sanded surface is dull by design. Compound and polish are what make it shine.
Shop wet/dry sanding sheets from 60 to 2000 grit, and polishing compounds for the finish.
