Sanding removes imperfections and dirt from surfaces and helps the paint stick better. So, do you have to sand between coats of stain?
Sanding between coats of stain isn’t necessary, but it’s recommended. That’s because the stain has good adhesive qualities, so paint bonding isn’t a problem. However, to get a perfect and smooth finish, you must sand between coats.
Water-based stains need to be sanded between coats since they raise the wood grain and cause bumps in the finish if you don’t.
Stain Dry Time Before Sanding
It takes stain 1-24 to dry enough for sanding, However, its dry time depends on the humidity, temperature, and type you used. For instance, the water-based type dries faster than the oil-based stain because it uses water as its solvent, and water evaporates faster than oil.
If you sand too soon, you will ruin the finish. That’s because if the coating is still wet, the particles haven’t hardened yet, so the coating will be sticky and wet. Once you use sandpaper over it, you will remove most of the stain and create a messy finish.
Use the sandpaper trick to know if the coating is dry enough. Swipe fine-grit sandpaper over the stain — if it gets clogged while sanding, the coating isn’t dry enough. If it moves smoothly over the coating, the coating is dry.
To sand between coats of oil-based stain, use a fine-sandpaper.
Oil-based stains use synthetic or natural oils as their solvent. Since oil takes a lot of time to evaporate, the stain has enough time to harden and cure. This allows the stain to stick better. However, sanding can improve the adhesion more and create a smoother finish.
If you take too long to apply another coat, then sanding is necessary. That’s because, while the coating is drying, dust and debris settle over it. So, if you don’t re-coat it fast enough, the coating will be full of dirt.
So, you must sand to remove the dust and dirt and create a smooth surface so the next coating can stick better.
You must sand between coats of water-based stain because it tends to raise the wood fibers as it dries. The raised wood fibers will become splinters and cause bumps in the finish. These bumps will prevent the next coating from sticking properly.
Also, the water-based stain is thin, so the raised wood fibers will affect it a lot more. Sanding will remove these bumps from the coating and leave a smooth surface behind for the next coating to stick to.
Related Read: How To Apply Stain With a Roller?
You shouldn’t sand the final coating. The final coat of stain gives the wood a unique color and beautifies it, so if you sand it, you will damage it and ruin the wood color.
Sanding between coats is recommended because it improves paint bonding and smoothness. If you apply multiple coats, it will help smoothen the coating so adhesion between them is improved.
However, the final coat of stain shouldn’t be sanded because you won’t apply a new coating over it. So, there’s no need to improve adhesion. Also, it will blur the finish because it will create dust and scratches over it.
These scratches will damage the smoothness of the final coat. The dust will make the finish blurry or cloudy, especially for clear stains. Eventually, you’ll be left with an amateurish finish.
If You Don’t Sand Between Coats:
If you don’t sand between coats of stain, the new coat won’t stick properly and the finish won’t be smooth or clear. That’s because the dust nibs, splinters, and debris will affect the quality of the finish.
Dust, debris, and splinters will settle and dry on the existing coating, making it difficult to have a smooth and perfectly bonded finish. This is why it’s required to sand lightly between coats, regardless of the type.
Sandpaper Grit To Use
You must use fine-grit sandpaper between coats, this includes grit of 320 and above. Avoid using coarse and medium-grit sandpaper as they will remove the coating instead of smoothing it out. This includes sandpaper with 150-grit and below.
You must apply stain in thin coats because thick coats will be difficult to control. So, if you sand thin coats with coarse or medium sandpaper, you will ruin the finish.
When sanding between coats, you need fine-grit sandpaper. That’s because you only need to remove the imperfections, dust, and debris from the coating, not the entire coating.
However, before staining wood, you must use medium-grit sandpaper. That’s because the wood has a lot of imperfections, bumps, and dirt on the surface, and medium-grit sandpaper will remove all of these. For rough timber wood, you can use 100-grit sandpaper.
Also, most wood furniture are riddled with glue, pencil marks, nail holes, and splinters. All of these things can affect the quality of the finish. So, you must use medium-grit sandpaper to remove all.
Fine-grit sandpaper won’t remove the large imperfections, pencil marks, or dirt from the wooden surface. You can only use fine-grit sandpaper if the wooden surface is smooth and even before staining.
Tip: Sand in the direction of the wood grain.
You must sand before and between coats of stain, but you shouldn’t sand the final coat. Sanding will help remove bumps from the surface and leave a smooth surface behind for the next coating to stick to.
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,