Sanding Between Coats of Semi-Gloss (Can You Do it?)

Semi-gloss has a glossy finish that repels liquid, including paint. So, do you need to sand between coats?

You must sand between coats of semi-gloss paint to remove its glossy finish so the new coat or paint can stick over it. When dry, semi-gloss paint will form a hard and moisture-resistant glossy that doesn’t accept paints. So, you must remove it before painting over it. 

If you don’t sand, the new coating won’t stick, will turn sticky for a few hours or days, and will peel off.

Semi-Gloss Paint Dry Time Before Sanding

Semi-gloss must dry enough for a re-coat before sanding. On average, this will take 2 hours. This gives the coating enough time to dry and harden to withstand the sanding pressure.

Semi-gloss paint dries through evaporation. This means the paint solvent (water or oil) must evaporate from the coating to get dry and hard enough to support another coating (or sanding).

The time it takes for the solvent to evaporate (or paint to dry) depends on the type (water or oil), room temperature, and humidity levels. Water-based paints dry faster because water evaporates faster. The higher the temperature and the lower the humidity levels, the faster the paint dries. 

If you sand semi-gloss paint that isn’t dry enough, the sandpaper will get clogged on the coating or the paint will get removed. This is because the paint coating won’t be hard (or durable) enough to withstand sanding. 

Sanding Between Coats

You must sand between coats of semi-gloss paint to remove the glossy finish and allow the new coating (or paint) to stick. Since semi-gloss paint has a high amount of sheen (or gloss), it forms a glossy finish that repels liquid, including paint.

So, if you apply paint over the glossy finish, the paint won’t be able to penetrate the coating and won’t stick. Sanding will remove the glossy layer, even (flat) out the surface, and remove imperfections, allowing the new coating to stick better. 

To sand between coats, use medium or fine-grit sandpaper, not coarse-grit sandpaper. That’s because coarse-grit sandpaper can remove the entire coating, while fine-grit sandpaper will remove the glossy layer only and smooth out the surface.

Sanding The Final (Last) Coat

You shouldn’t sand the final (last) coat of semi-gloss paint. That’s because the final coat reveals the glossy sheen of the paint and protects the surface underneath.

The final coat of paint is the protective layer of the finish that protects it from moisture, dents, or scratches. So,  if you sand the final coat, you will remove the protective layer and expose the surface underneath to different elements that can damage it. 

However, you must sand the final coat of semi-gloss if you want to apply another paint or sealant over it. That’s because no paint will stick over the glossy finish of semi-gloss, so you must sand it off (remove it) before applying.

If you want to apply a sealant, sanding is optional, but it helps to remove imperfections that the paint may have. Most sealants are clear coats and will reveal and highlight the imperfections underneath them. 

Sanding Before Applying The Paint

It’s recommended to sand before applying semi-gloss paint. That’s because most surfaces are uneven and riddled with imperfections or dust. So, sanding will remove the imperfections, creating a smooth and even (flat) surface for the paint to stick to. 

You must also sand if the surface is finished with a sealant or oil-based paint. That’s because sealant or oil-based paints have a glossy topcoat that repels liquid, including paint. So, you must sand off (remove) the sealant or oil-based topcoat before applying semi-gloss paint.

You must also sand if the surface has peeling water-based paint over it. Peeling paint will prevent good adhesion between the surface and new paint, so removing (or sanding) it is recommended. 

However, you can skip sanding if the surface is clean, even, dry, and isn’t finished or painted. Also, if the surface is finished with flat water-based paint or a primer, you don’t need to sand. 

If you apply semi-gloss without sanding first, the paint won’t stick or adhere to the surface properly. That’s because most surfaces are riddled with bumps, filth, or imperfections that prevent good adhesion. This will lead to semi-gloss paint not drying, turning sticky, or peeling off. 

Sandpaper Grits (Types) To Use

To sand between coats of semi-gloss paint, use fine-grit sandpaper. This includes sandpaper from 220-grit and upwards. The finer the sandpaper, the less it removes the paint and the more it smoothens the surface. 

To sand before applying paint, use medium or coarse-grit sandpaper. This includes sandpapers from 200-grit and downwards. Medium or coarse-grit sandpapers are strong enough to remove imperfections, bumps, dirt, and even paint from the surface. However, you shouldn’t use medium or coarse-grit sandpaper to sand between coatings as it can remove the entire coating.

The best way to sand while applying paint is to sand the surface with coarse-grit sandpaper (if it’s already finished with paint) or medium-grit sandpaper if the surface isn’t finished or painted. Apply one coat of paint, wait for it to dry, sand it with fine-grit sandpaper, and then apply the new coating (s). Once the final coat dries, sand it with ultrafine-grit sandpaper to remove small imperfections. 

Final Words

In summary, you must sand between coats of semi-gloss paint to remove its glossy layer that prevents the new coating from sticking. Sanding before applying the paint is also necessary, especially if the surface is already finished.

However, you shouldn’t sand the final coat as you can remove its protective top layer and decrease the paint’s durability.