Sanding Water-Based Paints: Can You Do It?

To get a better finish quality, you must sand between coats of paint. So, can you sand water-based paint?

You can sand water-based paint to improve paint adhesion and get an even finish. To sand water-based paint, use fine-grit sandpaper. Sanding removes imperfections from the surface and allows the paint to stick better. 

Sanding also removes paint bumps from the paint coating after it dries. However, it’s not always advised to sand water-based paints; let’s see why. 

Wait Time Before Sanding Water-based Paint

How long should you wait before sanding water-based paints? You should wait until the paint has dried. Usually, between 2 to 24 hours.

The water-based paint must cure and harden before you can sand it. Water-based paint cures within 24 hours. However, the cure time of water-based paints depends on the type and brand of the paint and the temperature. 

In a cold and humid temperature, the water-based paint takes longer to dry and cure. That’s because during humid temperatures there’s more water in the atmosphere which prevents the paint from drying. 

If you sand before the paint has dried, you will ruin the finish. Sanding water-based paint that hasn’t cured will scar the finish and make it cloudy. Also, sanding will remove most of the uncured paint. That’s because uncured paint hasn’t bonded (or hardened) properly to the surface, so sandpaper will remove most of it. 

To know if water-based paint is dry enough to sand, use the sandpaper trick. Swipe fine-grit sandpaper over the paint coating, if some of the paint gets removed, the paint hasn’t cured yet. If the paint doesn’t get removed, the paint has cured and you can sand it. 

Sanding Between Coats of Water-Based Paint

You should sand water-based paint. But, should you sand between coats of water-based paints?

You don’t need to sand between coats of water-based paint unless the surface has imperfections or bumps. When dry, water-based paint doesn’t produce a sheen or glossy finish, so you don’t need to sand it. The new coat of water-based paint will stick to the old one. 

When dry, water-based paint forms a dry and textured finish that doesn’t repel new paints. If you apply paint over the dry and textured finish of the water-based paint, the paint will stick properly. Since the water-based paint has a textured finish, you don’t need to sand between coats.

Also, water-based paint isn’t affected by dust or filth as much as oil-based paint. This is because water-based paints dry faster, so the paint isn’t wet long enough to attract dust or filth. 

However, if you paint over old water-based paint, you must sand it. That’s because the old paint coating has attracted too much dirt and dust over time, so a new paint won’t stick properly.

If you paint a vertical surface (such as a wall), you must sand between coats of water-based paint to prevent paint from dripping on the floor. 

Related Read: How To Sand Latex Paint?

Sanding Before Applying Water-Based Paint

You should sand between coats of water-based paints. But, should you sand the surface before applying water-based paint?

It’s not necessary to sand before applying water-based paint, but it’s recommended. Sanding before applying water-based paint increases the chances of getting a smooth and even finish. 

However, sanding before applying water-based paint is necessary if the surface is painted. That’s because the painted surface will have dust, filth, and imperfections that prevent good paint adhesion.

Also, if the surface to be painted is sealed with a topcoat, you must sand before applying a water-based paint. That’s because a sealed surface will prevent the water-based from sticking. Medium or coarse-grit sandpaper will remove the topcoat and create a smooth surface for the water-based paint to stick. 

To sand before applying water-based paint, use medium-grit sandpaper (120 or 150-grit). However, you must use coarse sandpaper if the surface is too dirty or uneven.

The only time you shouldn’t sand before applying water-based paint is if the surface is clean and even. Water-based paint has impressive qualities and will stick to a clean and even surface without sanding. 

Wet Sand vs Dry Sand (For Water-Based Paint)

You must wet sand the last coat of the water-based paint because wet sanding is less abrasive and won’t scar the finish. However, you must dry sand between coats of water-based paint. That’s because dry sanding smoothes rough paint coatings faster. 

Dry sanding is done by rubbing fine-grit sandpaper against the water-based paint coating after it has cured. To dry sand, you just need fine-grit sandpaper, nothing else. 

To wet sand, you must rub waterproof fine-grit sandpaper against the water-based paint coating. You must also pour lubricant (water) over the paint coating before sanding. During wet sanding, you remove less material, and the sanding process produces less dust. That’s why you must wet-sand the final coat of water-based paint.

However, you must dry sand between coats of water-based paint. That’s because dry sanding will remove imperfection better than wet sanding. Also, dry sanding is more abrasive and will scar the water-based paint coating. These scars allow the next coating to stick better. 

If you dry sand the final coat of water-based paint, you will scar the finish.

Related Read: Sanding Chalk Paint?

Sandpaper Types To Use

What Type Of Sandpaper Should You Use To Sand Water-Based Paint?

You must use fine-grit (240-grit+) sandpaper to sand water-based paint. Fine-grit sandpaper is designed with tiny bristles that won’t cause any damage to the water-based coating.

The fine-grit sandpaper will remove the bumps or imperfections over the paint coating, but won’t remove the paint. It will also remove bumps, dust, and brush marks from the paint coating. The fine-grit sandpaper will abrade the finish by creating tiny scars that allow the next  paint coating to stick better. 

However, if you use coarse or medium-grit sandpaper, you will scar and peel the water-based paint. The coarse or medium-grit sandpaper is strong enough to remove the water-based paint coating. You must only use coarse or medium-grit sandpaper before applying the water-based paint. 

Sanding Water-Based Primer

You can sand a water-based primer to smoothen it after it has dried. However, sanding a water-based primer isn’t necessary. That’s because primer has impressive bonding qualities and is thick enough to cover most imperfections. 

But, if you apply thin coats of primer, you must sand it before applying paint. That’s because imperfections such as raised fibers and splinters will show over the thin coat of primer. But, sanding will remove most of the imperfections from the primer coating. 

In other words, sanding water-based primer isn’t necessary, but it’s still recommended to get a good finish quality.

To sand a water-based primer, use very fine-grit sandpaper such as 400-grit and above.

Related Read: Does Water-Based Paint Expire?

Final Words

You can sand water-based paint, but only after the paint has cured. To sand water-based paint, use fine-grit sandpaper. You must dry sand between coats of water-based paint, but you must wet-sand the final coat of the paint. 

Leave a Comment