Wet sanding — also called wet flatting — is a technique where you use water as a lubricant to refine the final paint coat. The result: a mirror-smooth surface ready for polishing. Here is how to approach it.
When to wet-sand?
After the final coat has fully cured — minimum 24 hours for 2K paint, minimum 48 hours for water-based paint. Starting too early draws moisture into the paint, causing white spots and damage.
Materials
- Sandpaper P800–P2000, depending on the starting quality of the paint
- Clean water with a drop of dish soap (reduces friction)
- A soft sanding block or interface pad for even pressure
- Microfibre cloths for intermediate drying and inspection
Procedure
- Start with P800 or P1000 if the paint has orange peel or dust nibs. If the paint already has a good surface, start at P1500.
- Soak the paper for five minutes in water before use. This makes it more pliable and prevents tearing.
- Sand in straight lines, never in circles. Cross the direction after each step to detect irregularities.
- Rinse regularly — accumulated slurry sands back and causes scratches.
- Dry and inspect under raking light after each grit step before continuing.
- Work up to P2000 and then move on to machine or hand polishing.
Common mistake
Pressing too hard. Wet sanding works on even, light pressure. Heavy pressure sands too deep and rounds the surface. Let the paper do the work.