Painting your new home in your favorite color is exciting but also a little daunting as you want to get it right. So is it necessary to sand between paint coats?
Sanding walls between coats of paint isn’t always necessary, but it will make your paint job look smoother. Sanding rough spots on walls ensures that the paint can adhere properly, which results in a smooth finish. It’s not recommended to sand latex-based paints as it removes too much of the paint from the wall.
In this article, I’m going to show you:
- When sanding is necessary
- Which sandpaper grade you need
- How long to allow the paint to dry before sanding
- Dangers of sanding latex paint
When should you sand walls between paint coats?
It’s important to sand your walls, but it’s equally important to know when is the correct time to do so. Sanding too much can ruin your wall, while never doing it could lead to a poor paint finish.
Whenever you are painting a wall, it will often have a textured appearance. This happens because the paint builds up on a wall while you are painting, usually because you’ve had too much paint on the roller.
Paint build-up is a regular occurrence as people commonly dip the roller into the paint too much as the paint begins to look more textured on the wall, rather than smooth.
The more you dip the roller in the paint, the thicker the roller becomes, which makes it work less efficiently and causes the textured or bumpy paint appearance on the wall.
Sanding oil-based paints
This is because oil-based paint is usually very smooth, which means that any paint you try to use over the top of it will struggle to stick.
When sanding your wall, you should wrap the sandpaper around a sanding block so that it’s easier to use. You don’t need to strip the wall completely with your sandpaper. You only need to make it rough enough that the fresh paint will stick to the old oil-based paint that is currently on the wall.
What paint is on your walls?
If you’re not sure whether your existing paint is oil-based, you can easily find out by using some warm water, detergent, and cotton wool. Wash a small area with the water and detergent, then soak some cotton wool in rubbing alcohol and use it to dab the wall with.
If your cotton wool comes away with paint on it, then you have latex-based paint on your wall. But if no paint comes off, then it is oil-based paint. If it is latex-based paint on your wall, then you don’t need to sand it first.
It’s not just built-up paint that can cause your wall to become bumpy but roller texture too. Often, people add texture to walls to make them look different, but this can also be removed by a bit of gentle sanding.
Which sandpaper grade should I use between coats of paint?
The best sandpaper to use for sanding walls between coats is 100- to 150-grit. I like this medium-range sandpaper, which is excellent for most jobs. It allows you to take more material off by using more pressure or smooth materials by using less pressure.
It’s important to always make sure that you are using the correct level of sandpaper for the job when sanding a wall, as sandpaper that is too coarse can damage the paint.
With sandpaper, the lower the number, the coarser the grit. For example, 1000-grit sandpaper is extremely fine while 100-grit is much coarser.
Coarse sandpaper requires much less effort on materials such as wood than higher grit sandpaper does. Higher grit sandpapers smooth surfaces rather than removing a lot of material.
Is it necessary to sand between coats of latex paint?
It’s not really effective to sand your wall between coats of latex paint. This is because it doesn’t just remove the texture from the walls but will remove all of the paint too. If you’ve got brush marks you don’t want on your wall, then you should strip all of the paint off and begin again afresh.
A foam roller is ideal to use for painting the new coat as it doesn’t leave as many marks or textures behind. Alternatively, you could mix some Floetrol with the paint.
You should still sand your doors and cabinets between coats even though you’re not sanding your wall as it will improve their shine and overall appeal.
It’s always important to only sand when it is dry and the temperature is between 70 and 80°F (21-27°C). It’s also best to do it when the humidity is less than 70%.
When sanding fresh latex-based paint, you should use either a fine to medium sanding sponge or 120 to 150-grit sandpaper. When sanding cured latex-based paint, you can use sandpaper with a coarser grit.
You shouldn’t use coarse grit sandpaper on fresh paint as it can scratch it easily. Latex-based paint usually takes around 30 days to cure properly.
How long should the paint be left to dry before sanding?
You should never rush into sanding, and you should always make sure that you have allowed plenty of time for the paint to dry.
Whether your paint contains water or not can determine how long it needs to dry. Oil-based paint takes much longer to dry than water-based paint. This is because water evaporates from latex paint, which allows it to dry much quicker than oil-based paint that does not contain water.
Paint contains binders that hold the pigments in the paint together. Glossy paint contains more binders than flat paint and takes longer to dry, while flat paint dries the quickest. Therefore, semi-gloss is mid-range both in sheen and drying time.
Although most paints are usually dry enough for a second coat to be applied after a couple of hours, you should always wait between 12 and 24 hours before you sand it and then apply the next coat. It’s important to check how long your specific paint type requires to dry so you don’t sand it too soon.
It is possible to dry your paint quicker by keeping the room at a certain temperature. Water-based paints dry well at around 72°F (22°C), while oil-based paint dries best if the temperature is between 50 and 90°F (10-32°C).
However, the room should never be cold as that can increase the humidity. This causes water-based paint to take longer to dry as the water needs to be able to evaporate first.
So long as there are no extremes of temperature outside and the humidity is low, then opening the windows can speed up the drying process of your paint, as can a fan switched onto a low setting.
Is it dangerous to sand latex paint?
Although latex paints do contain solvents and chemicals that can be harmful, they are water-based paints and are far safer to use than paint that is solvent-based.
However, crystalline silica is an ingredient in latex paint, which can be dangerous to sand as there is the risk of it causing scarring and growths in your lungs.
If you are exposed to a lot of crystalline silica over a long period of time, it can cause silicosis, which turns into lung cancer. Therefore, it is extremely important to wear an air respirator when sanding latex-based paint.
An air respirator is different from a dust mask as it will filter out the crystalline silica while a dust mask does not.
There are a few other risks involved with sanding latex-based paint as older walls can often contain toxic lead or mercury.
It’s important to make sure that you never use outdoor latex-based paint inside your home as it often contains biocides to prevent the growth of mold.
Also, indoor latex-based paint contains formaldehyde, which can outgas as the paint dries. If you breathe in formaldehyde, it can cause irritation in your nose, throat, and eyes, and dizziness, sickness, and headaches.
Therefore, whenever you are using latex-based paint, you should always work with all of the windows open to let fresh air in and paint fumes out. Also, you should always try to allow plenty of ventilation while the paint is drying as it can produce harmful vapors during the drying process.