Should You Sand Walls Between Coats Of Paint?

 H2: Should you sand walls between coats of paint?

It’s important to sand your walls, but it’s equally important to know when is the correct time to sand them - sanding too often could ruin your wall, while never doing it could lead to the paint looking poor.

 

Whenever you are painting a wall, it will often have a textured appearance and this happens because the paint builds up on a wall when you are painting - usually when you’ve had too much paint on the roller.  Paint build-up is a regular occurrence as it’s people commonly dip the roller into the paint more often as it 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.

 

One of the most important things to know about painting a wall is that you will need to sand the wall before painting if you are planning to paint over an oil-based paint with a latex-based paint.  This is because oil-based paint is usually very smooth which means that any paint you try to use over the top of it struggles to stick.

 

When sanding your wall, you should wrap the sandpaper around a block so that it is 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 there.

 

If you’re not sure whether your existing paint is oil-based then 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 a latex-based paint on your wall, but if no paint comes off then it is an 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.

 

H2: Should you sand between coats of latex paint?

It’s not really effective to sand your wall between coats of latex paint as it doesn’t just remove the texture from the walls it will remove all of the paint too.  Therefore, 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 degrees Fahrenheit.  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 that is 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.

 

H2: How long should paint be left to dry before sanding?

You should never rush into sanding anything and you should always make sure that you have allowed plenty of time for the paint to dry before beginning to sand it.  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 which does not contain water.

 

Paint contains binders that hold, or bind, the pigments in the paint together.  Glossy paint contains more binders than flat paints 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 degrees Fahrenheit, while oil-based paint dries best if the temperature is between 50 and 90 degrees.  However, the room should never be cold as that can increase the humidity which would cause water-based paint to take longer to dry as the water needs to be able to evaporate for the paint to dry.

 

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.

 

H2: Which sandpaper grade should I use between coats of paint?

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 24 grit is much courser.

 

Coarser - or lower number - sandpaper requires much less effort on materials such as wood than higher grit sandpaper does.  Higher grit sandpaper doesn’t remove much material and smooths surfaces rather than removing a lot of material.

 

The best sandpaper to use for sanding walls between coats is 100 to 150 grit.  This is a medium-range sandpaper and is used for most jobs as you can take more material off with it by using more pressure and more effort, or you can smooth materials with it by using less pressure.

 

H2: 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 and it 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, or over a long period of time, then 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 to a dust mask as it will filter out the crystalline silica while a dusk 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 mould.

 

Also, indoor latex-based paint contains formaldehyde and as the paint dries it can produce this as an outgas.  If you breathe it formaldehyde then 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 in while the paint is drying as it can produce harmful vapours during the drying process.