Sanding Latex Paint (Before & After Applying): Is It Necessary?

Sanding removes imperfections and bumps from the surface, allowing the paint to stick to an even and clean surface. So, should you sand latex paint?

You must sand latex paint if you are painting over a bumpy surface. The bumps or imperfections will prevent latex paint from sticking properly. However, sanding will remove those imperfections. 

You must also sand if the surface is painted or sealed. You can’t apply latex paint over a sealed or painted surface. Sanding will remove the glossy layer of a sealer and create tiny ridges for latex paint to stick to. 

Latex Dry Time Before Sanding

You must sand latex paint after it has fully dried. It takes latex paint 3 hours to dry fully. Latex paint is water-based, so the paint dries faster than most paints.

To dry, the paint solvent (water) of latex paint must evaporate. Once the paint solvent evaporates, the paint particles start to harden, and the latex paint coating becomes rigid. Once the latex paint is rigid, you can sand it.

If you sand before the latex paint has dried, you will ruin the finish. If the paint solvent isn’t evaporated and the paint particles haven’t hardened, sandpaper will remove the entire coating rather than sand it. Also, if the latex paint isn’t dry, the coating is still wet, and if you use sandpaper over it, the paint will stick over the sandpaper and clog it.

To know if the latex paint is dry enough for sanding, feel the texture using your hand. If the latex paint coating feels dry and textured, it means it has dried, and you can sand it. On the other hand, if the latex paint texture feels wet and paint sticks in your hand, the latex paint hasn’t dried (yet), and you can’t sand it.

You can also use fine-grit sandpaper to know if latex paint is dry or not. Swipe the fine-grit sandpaper over the latex coating; if the sandpaper starts to clog, it means the latex paint isn’t dry yet. If the sandpaper goes smoothly over the coating, the latex paint is dry, and you can sand it. You must use fine-grit sandpaper for this and not coarse sandpaper.

Sanding Between Coats of Latex Paint

Sanding latex paint between coats isn’t mandatory. However, sanding will help latex paint to stick better and provide a smoother finish. 

While the latex paint coating is drying, dust and nibs will settle over the coating. If you apply the next coating without sanding, the new latex paint will have bubbles on its finish (because of the dust).

However, sanding will remove the dust and other imperfections from the latex paint coating and allow the new coating to stick to a smooth and even surface. As an alternative to sanding, you can use a clean rag to remove the dust from the latex paint coating and then apply the next paint coating. 

Sanding The Last Coat of Latex Paint

You shouldn’t sand the final coat of latex paint. That’s because the last coat will reveal the color of latex paint. If you sand the last coat of latex paint, the finish will look discolored and scratched.

Except for bumps in the paint coating, sanding also removes some layers of the paint. So, if you sand the last coat of latex paint, sanding will remove the bright shade of the latex paint. As a result, the finish will look old and scratched. Also, sanding will weaken the latex paint and cause the coating to peel off (wash off) easier. 

But, you can sand the final coating of latex paint if you will apply a sealer over it. Since most sealers are clear coats (have no color), they will reveal imperfections and bumps on the surface. So, sanding latex paint before applying a sealer will remove the imperfections from the surface and allow the sealer to stick properly. 

Sanding Before Applying Latex Paint

To get a better finish, you must sand before applying latex paint. Though latex paint has impressive bonding qualities, the paint won’t stick properly to a dirty surface. So, sanding will remove the imperfections (and dirt) from the surface and create a smooth layer for latex paint to stick to.

Also, you must sand if the surface is already painted or sealed. That’s because the latex paint won’t stick to oil-based paint or sealer. A sealer, such as polyurethane, forms a glossy and thick layer that repels moisture, including paint. So, if you apply latex paint over a sealed surface, the glossy layer of the sealer will prevent the latex paint from penetrating, so latex paint won’t stick. 

However, if the surface is painted with water-based paint, you can apply latex paint without sanding. But, the surface must be even and have no imperfections. If that’s the case, you must clean the surface with a clean rag, let it dry, and then apply the latex paint.

Final Words

Overall, sanding latex paint is necessary if the surface is dirty, dusted, or uneven. Sanding will remove the imperfections from the surface and help latex paint stick better. Also, if the surface is painted with oil-based paint or sealer, you must sand before applying latex paint. 

To sand between coats of latex paint, use fine-grit sandpaper. Fine-grit sandpaper won’t remove the paint coating; instead, it will smoothen the layer. To sand before applying latex paint, use coarse-grit sandpaper. Coarse sandpaper will remove old paint and even out the surface.

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