Sanding improves the paint adhesion and smoothness of the finish. But, since chalk paint has impressive bonding qualities, should you sand it?
You can sand before applying, between coats, and after applying chalk paint. It will create a smooth surface for the paint to stick to. Sanding between coats will also help the next coat to stick better. Also, sanding the final coat will create a distressed finish.
However, you must know the right type of sandpaper to use. If you use coarse sandpaper, you will remove the finish.
Sanding between coats is optional because chalk paint has a dry textured finish that allows new paint to stick with ease. Also, the paint has impressive bonding qualities so it will stick over any surface.
However, a light sanding between coats will help/boost the smoothness of the finish. It will create small scratches that the new coating can stick to, remove imperfections, and bumps, and leave behind an even surface.
To sand between coats of chalk paint, use fine-grit sandpaper. The fine-grit sandpaper is coarse enough to remove paint bumps and imperfections, but not strong enough to remove the finish. Avoid using coarse-grit sandpaper as it can remove the entire coating.
Related Read: Does Chalk Paint Scratch Easily?
Chalk Paint Dry Time Before Sanding
Chalk paint must dry for 30 minutes before sanding. This gives its coating enough time to harden and dry to support sanding. However, the dry time depends on the humidity levels, number and thickness of the coats, and room temperature.
Chalk paint dries through evaporation, meaning the paint solvent (water) must evaporate. Since chalk paint is water-based and uses water as its solvent, the paint dries fast because water evaporates fast. If you sand it too soon, you will damage the finish. Sanding a wet coating will remove it and make the finish tacky or sticky.
To know if chalk paint is dry enough for sanding, use the sandpaper trick. Swipe ultrafine-grit sandpaper across the finish (after 30 minutes); if the sandpaper gets clogged, the paint isn’t dry enough. If the sandpaper swipes with ease (doesn’t get clogged), the paint is ready to be sanded.
Here are the tools you need:
- Fine-Grit sandpaper or Sanding Block
- Soft Brush
- Face Mask
1. Clean The Finish
First, clean the finish. Cleaning will remove dust, debris, and filth from the coating which can prevent a good sanding result.
To clean the chalk paint finish, use a soft brush or lint-free cloth to sweep the coating. The paint isn’t durable, so don’t use tools that can abrade or scar the finish.
2. Sand it
To sand chalk paint:
- Use fine-grit sandpaper (400-grit).
- Swipe the sandpaper across the coating.
- Don’t apply pressure while sanding.
- If sanding between coats, move the sandpaper back and forth over the coating to create tiny scratches.
- If sanding the final coat, don’t move the sandpaper back and forth repeatedly. Instead, sand it with one swipe.
You shouldn’t sand the final coat repeatedly because you aren’t trying to create holes or pores. Instead, you want to make the final coating as smooth as possible.
3. Vacuum The Dust
After sanding the chalk paint finish, remove the dust by using a vacuum. Sanding creates a lot of dust that can prevent the next coat from sticking.
Related Read: How To Paint Over Chalk Paint?
4. Inspect The Finish
After sanding and cleaning the finish, inspect it. If the coating is smooth enough, you don’t have to sand it anymore. If the coating has bumps or imperfections, sand it again. But, this time use 320-grit sandpaper.
- You can re-coat the paint immediately after dry sanding.
- The finish won’t get removed.
- It produces a lot of dust.
- The sanding result isn’t as smooth.
Wet sanding chalk paint is different from dry sanding it. To dry sand, you must wait until the paint solvent evaporates and the coating gets hardened. But, for wet sanding, the chalk paint must be cured (dry fully) because water can wash it off.
Here are the tools you need:
- A Bowl Of Water
- Waterproof sandpaper Or Sanding Sponge
- A Dry Towel
1. Prep The Paint & Sandpaper
First, clean the finish. Use a clean rag and wipe off the dust from the coating.
Next, wet the waterproof sandpaper:
- Dip the waterproof sandpaper into water.
- Wait 2 minutes.
- Take the waterproof sandpaper off the water.
- Squeeze it to remove excess water.
- The sandpaper must be damp, not dripping wet. If it’s dripping wet, it will damage the paint.
Lay the abrasive side of the waterproof sandpaper over the finish and move it lightly. Ensure not to apply much pressure so the finish doesn’t get removed.
While sanding, dust will start to stick to the sandpaper. Sand until the waterproof sandpaper accumulates too much dust (where you can’t sand anymore), and then stop, dip the sandpaper into the water again, and start again. You must do this often.
3. Let The Paint Dry
After wet sanding the chalk paint, leave it to dry. This will take a few minutes. When the paint dries, inspect the finish and check if you have a desired level of smoothness. If the finish isn’t smooth enough, wet sand it again.
- Wet sanding doesn’t produce a lot of dust
- It creates a smoother finish.
- The paint can get washed off if you use too much water.
- You must wait until the paint cures before wet sanding (which takes longer).
- You must wait until the coat dries to re-coat it.
Sanding Before Chalk Paint
You must sand before applying chalk paint to remove imperfections from the surface and help the paint stick better. Sanding before painting is mandatory for non-porous surfaces whether the surface is clean or not.
However, if the surface is clean, smooth, and porous, sanding isn’t necessary. That’s because chalk paint has impressive bonding qualities and will stick to most surfaces.
You must also clean the surface before painting it. That’s because most surfaces are dirty and riddled with dust that can prevent the paint from sticking. To clean a surface, use soapy water, wait for it to dry, and then apply the paint.
If the surface is painted or sealed, you must remove the existing finish. That’s because the existing finish will prevent chalk paint from sticking. To remove an existing finish, use coarse-grit sandpaper.
So, sanding before painting is required only if the surface is dirty, already painted (finished), or for non-porous surfaces.
Sanding The Final Coat
Sanding the final coat of chalk paint is optional. You can sand the final coat if you want a distressed finish or if you want to apply another paint (or sealant) over it. However, if the chalk paint is the final coat, you don’t have to sand it as you risk damaging the finish.
To sand the final coat, use ultrafine-grit sandpaper (800-grit). This sandpaper will lightly sand the coating, and remove imperfections, paint bumps, or brush marks. Don’t use coarse-grit sandpaper over the final coating as you can remove the entire finish.
You can also sand the final coating if you want to seal it. While a sealant will stick over paint regardless, light sand will improve the bonding and prevent imperfections from showing once the sealant dries.
Sanding Won’t Damage The Finish
If you use the right type of sandpaper (grit) you won’t damage the chalk paint. However, if you use the wrong sandpaper, you will damage the finish.
Sandpapers come in different grits. For instance, ultrafine-grit sandpaper is made to smoothen a surface and remove imperfections. On the other hand, coarse-grit sandpaper is made to remove a finish from the surface. So, if you use the right type of sandpaper, you won’t damage the finish.
Here are the sandpaper grits you need:
- Before applying chalk paint, use coarse-grit sandpaper (150/180-grit).
- For between coats of paint, use fine-grit sandpaper (300/400-grit).
- For the final coat of the paint, use ultrafine-grit sandpaper (800-grit).
You can sand before, between coats, and after applying chalk paint. It will improve the adhesion between the surface and the paint, and remove imperfections from the coating. However, the paint must dry fully and you must use the right type of sandpaper.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,